All posts by John Goerzen

Voice Keying with bash, sox, and aplay

Debian, Linux, Programming, Technology, ,

There are plenty of times where it is nice to have Linux transmit things out a radio. One obvious example is the digital communication modes, where software acts as a sort of modem. A prominent example of this in Debian is fldigi.

Sometimes, it is nice to transmit voice instead of a digital signal. This is called voice keying. When operating a contest, for instance, a person might call CQ over and over, with just some brief gaps.

Most people that interface a radio with a computer use a sound card interface of some sort. The more modern of these have a simple USB cable that connects to the computer and acts as a USB sound card. So, at a certain level, all that you have to do is play sound out a specific device.

But it’s not quite so easy, because there is one other wrinkle: you have to engage the radio’s transmitter. This is obviously not something that is part of typical sound card APIs. There are all sorts of ways to do it, ranging from dedicated serial or parallel port circuits involving asserting voltage on certain pins, to voice-activated (VOX) circuits.

I have used two of these interfaces: the basic Signalink USB and the more powerful RigExpert TI-5. The Signalink USB integrates a VOX circuit and provides cabling to engage the transmitter when VOX is tripped. The TI-5, on the other hand, emulates three USB serial ports, and if you raise RTS on one of them, it will keep the transmitter engaged as long as RTS is high. This is a more accurate and precise approach.

VOX-based voice keying with the Signalink USB

But let’s first look at the Signalink USB case. The problem here is that its VOX circuit is really tuned for digital transmissions, which tend to be either really loud or completely silent. Human speech rises and falls in volume, and it tends to rapidly assert and drop PTT (Push-To-Talk, the name for the control that engages the radio’s transmitter) when used with VOX.

The solution I hit on was to add a constant, loud tone to the transmitted audio, but one which is outside the range of frequencies that the radio will transmit (which is usually no higher than 3kHz). This can be done using sox and aplay, the ALSA player. Here’s my script to call cq with Signalink USB:

#!/bin/bash
# NOTE: use alsamixer and set playback gain to 99
set -e

playcmd () {
        sox -V0 -m "$1" \
           "| sox -V0 -r 44100 $1 -t wav -c 1 -   synth sine 20000 gain -1" \
            -t wav - | \
           aplay -q  -D default:CARD=CODEC
}

DELAY=${1:-1.5}

echo -n "Started at: "
date

STARTTIME=`date +%s`
while true; do
        printf "\r"
        echo -n $(( (`date +%s`-$STARTTIME) / 60))
        printf "m/${DELAY}s: TRANSMIT"
        playcmd ~/audio/cq/cq.wav
        printf "\r"
        echo -n $(( (`date +%s`-$STARTTIME) / 60))
        printf "m/${DELAY}s: off         "
        sleep $DELAY
done

Run this, and it will continuously play your message, with a 1.5s gap in between during which the transmitter is not keyed.

The screen will look like this:

Started at: Fri Aug 24 21:17:47 CDT 2012
2m/1.5s: off

The 2m is how long it’s been going this time, and the 1.5s shows the configured gap.

The sox commands are really two nested ones. The -m causes sox to merge the .wav file in $1 with the 20kHz sine wave being generated, and the entire thing is piped to the ALSA player.

Tweaks for RigExpert TI-5

This is actually a much simpler case. We just replace playcmd as follows:

playcmd () {
        ~/bin/raiserts /dev/ttyUSB1 'aplay -q -D default:CARD=CODEC' < "$1"
}

Where raiserts is a program that simply keeps RTS asserted on the serial port while the given command executes. Here's its source, which I modified a bit from a program I found online:

/* modified from
 * https://www.linuxquestions.org/questions/programming-9/manually-controlling-rts-cts-326590/
 * */
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 


static struct termios oldterminfo;


void closeserial(int fd)
{
    tcsetattr(fd, TCSANOW, &oldterminfo);
    if (close(fd) < 0)
        perror("closeserial()");
}


int openserial(char *devicename)
{
    int fd;
    struct termios attr;

    if ((fd = open(devicename, O_RDWR)) == -1) {
        perror("openserial(): open()");
        return 0;
    }
    if (tcgetattr(fd, &oldterminfo) == -1) {
        perror("openserial(): tcgetattr()");
        return 0;
    }
    attr = oldterminfo;
    attr.c_cflag |= CRTSCTS | CLOCAL;
    attr.c_oflag = 0;
    if (tcflush(fd, TCIOFLUSH) == -1) {
        perror("openserial(): tcflush()");
        return 0;
    }
    if (tcsetattr(fd, TCSANOW, &attr) == -1) {
        perror("initserial(): tcsetattr()");
        return 0;
    }
    return fd;
}


int setRTS(int fd, int level)
{
    int status;

    if (ioctl(fd, TIOCMGET, &status) == -1) {
        perror("setRTS(): TIOCMGET");
        return 0;
    }
    status &= ~TIOCM_DTR;   /* ALWAYS clear DTR */
    if (level)
        status |= TIOCM_RTS;
    else
        status &= ~TIOCM_RTS;
    if (ioctl(fd, TIOCMSET, &status) == -1) {
        perror("setRTS(): TIOCMSET");
        return 0;
    }
    return 1;
}


int main(int argc, char *argv[])
{
    int fd, retval;
    char *serialdev;

    if (argc < 3) {
        printf("Syntax: raiserts /dev/ttyname 'command to run while RTS held'\n");
        return 5;
    }
    serialdev = argv[1];
    fd = openserial(serialdev);
    if (!fd) {
        fprintf(stderr, "Error while initializing %s.\n", serialdev);
        return 1;
    }

    setRTS(fd, 1);
    retval = system(argv[2]);
    setRTS(fd, 0);

    closeserial(fd);
    return retval;
}

This compiles to an executable less than 10K in size. I love it when that happens.

So these examples support voice keying both with VOX circuits and with serial-controlled PTT. raiserts.c could be trivially modified to control other serial pins as well, should you have an interface which uses different ones.

Crazy Enough?

General, Society

So far this year, I’ve read somewhere in the neighborhood of 5000 pages. As I’ve started to read more, I’ve started to watch TV, movies, and Youtube less, because they are simply boring and shallow in comparison. War and Peace, in particular, deeply touched me. Lately I have been reading the Wheel of Time series, which has its own unique characteristics.

Whether an epic (or super-epic, such as Wheel of Time) novel, or the Sherlock Holmes series, or nonfiction works, there is something magical about reading a book. We often see characters, real or fictional, that rise from obscurity to do great things for the world. We are transported in time and place to a time or place we will never be able to experience, perhaps because it is long past, or perhaps because it never was. But in any case, we can be inspired.

I am reminded of this quote:

“The people crazy enough to think they can change the world are the ones that do.”

If someone told me that a street vendor in Tunisia would, in less than a year, cause the overthrow of 4 dictatorships and reform in a handful more, I would have, yes, thought that was crazy. And while Mohamed Bouazizi isn’t a household name in much of the world, he managed exactly that. But not just him. It took crazy unarmed people to occupy Tahrir Square, some to die, for progress to be made in Egypt.

This story is written all over history. People have done the impossible, have defied all odds, through sheer belief that they could. Civil rights have been granted due to the leaders we all know, but also due to the millions of marchers we don’t. Changing the world doesn’t have to mean that the world knows you. It just has to mean that you love the world, as Tolstoy pointed out:

Love hinders death. Love is life. All, everything that I understand, I understand only because I love. Everything is, everything exists, only because I love. Everything is united by it alone. Love is God, and to die means that I, a particle of love, shall return to the general and eternal source.

Whatever your stance on religion, this is a powerful quote. Sometimes particles of love might look crazy. But isn’t it then that they are the most alive? Isn’t it then that they are the greatest hindrance to death and despair?

Summer

Family, Outdoors

It’s been a hot year in Kansas this year. Really hot. Our average high for July was 101F / 38C. It’s also been extremely dry. So we haven’t had too many pleasant opportunities to enjoy a bit of an upcycling project I had with the boys.

When we renovated our old farmhouse, we had two chimneys removed. The bricks were saved in a large pile out back, and we haven’t really touched them in the last 5 years.

I got the idea at some point that it would be nice to have a fire ring on our yard. The boys love campfire-style cooking, and enjoy helping gather kindling and watching the fire grow. I had looked at fire rings in stores, but just couldn’t bring myself to pay $60 or $100 or even more for what was really a piece of round metal. I decided we would find a way to build our own fire ring.

So the idea of chimney bricks seemed perfect. Some of these bricks still have mortar on them, so the result is imperfect, but it is functional. More importantly, the boys helped. They picked out bricks one at a time, set them in the wheelbarrow (or even carried a few themselves, as Jacob insisted on doing sometimes.) Then we’d dump them out on the ground, and I’d make some attempt at making the thing round, while the boys would put them on the pile.

We did this over the course of several evenings, with me filling in on some of it after they lost interest. When we got it done, they of course loved cooking outside. I made sure that we placed it in a place that will be in the shade every summer evening so we’d be comfortable. I made no attempt to mortar it in; this way, it’s easy to move or resize. And it’s safer for the boys than a metal one, since the outer edge never even gets warm to the touch.

Anyhow, it finally got a little cooler last week, so we cooked out there for dinner two days in a row. One day, after eating, the boys came back out to help put out the fire with the hose. After that, Jacob and I went out there to eat dessert. He sat on the grass, and I sat down next to him. He scooted over a bit to be closer to me. Pretty soon, Oliver came running out too, and sat on my lap. The three of us just sat there on the grass, eating our desserts and enjoying the evening. It’s the kind of moment that makes a dad happy.

The other evening, they again helped me put out the fire with a hose. They’d been active that day, so after I finished hosing down the fire ring, I gave them each a small spray with the hose. After a brief flicker of indecision, they both decided this was hilarious. Jacob took off running, yelling “You’ll never catch me!” (And clearly hoping I would.) Oliver copied him, and so I proceeded to chase them around the yard with a hose for quite awhile. There was much laughter from them, and they wound up totally soaked and happy. Another good evening. You never know what will happen outdoors, but so often it is very good.

A Verbose, Hands-On Nexus 7 Review

Hardware, Reviews

Some of you may have noticed that I am not a concise author. Perhaps that has something to do with the fact that I am not a concise reader. I like facts, details, and lots of them. So as a recent Nexus 7 purchaser, here you go.

Genesis

I’ve long used Android devices, and last year had a company-issued Motorola Xoom, which was the first Google Experience tablet with Honeycomb. That tablet has specs roughly similar to iPads; its 10.1″ screen was the same, the 1280×800 screen was better than the iPad available at the time, and its 730g weight identical to the early iPads (though 10% higher than the current iPad). I lost access to it when I changed jobs, and had been without a tablet until recently.

Other devices I own are the Galaxy Nexus, sporting a 4.65″ screen; and what’s now called the Kindle Keyboard, with an eInk screen.

I had been somewhat interested in the Kindle Fire, but the closed nature and limited capability of the system kept me away.

The Nexus 7 reviews, however, were stunning, as was the price. $200 for a great tablet. I wound up buying the $250 16GB model. But not until after I spent a great deal of time thinking about size.

Physical Size

My main concern was that the Nexus 7 would be too small to be useful. I had never been particularly pleased with my input speed on the Xoom. I tried to touch type on it, but was just never fast enough to surpass “frustratingly slow.” I have long been a fast and accurate typist on keyboard; well over 100 words per minute, and it is frustrating when my fingers can’t maintain that speed.

I figured the situation would be even worse on the Nexus 7, given its smaller size.

I also found the Xoom to sometimes feel a little small with the 10″ screen, and was concerned about that as well.

And finally, 7″ doesn’t sound all that much larger than 4.65″.

However, having actually had the Nexus 7 for a little while now, I’m very pleased with the size, and may even prefer it. The 10″ tablets are just too big and heavy to comfortably hold in one hand, and I’ve realized that part of my Xoom frustration was the fact that I had to set it down and prop it up for anything beyond very brief use. At 340g, the Nexus 7 is less than half the weight of the Xoom or iPad, and it makes a huge difference. While still nowhere near where I’d be with a keyboard, two-thumb typing in portrait mode, or even something approaching touch typing in landscape mode, is possible on the Nexus 7.

The screen size hasn’t been a bother, at all. This may be due to the fact that it’s higher resolution (it’s 1280×800 like the Xoom, but those pixels are crammed into only 7″). I think it’s also partly due to the fact that the browser in Jelly Bean is significantly better than the one in Honeycomb, and perhaps that websites are better at tablet-friendliness, too.

Overall, the Nexus 7 feels a lot farther from the size of a laptop than did the Xoom, and as such is more prone to come with me in lots of situations, I think.

It works reasonably well with foldable Bluetooth keyboards, so when thinking about a laptop replacement or alternative, that might be the way I go. A Bluetooth mouse also works with it, though I found it didn’t provide near the utility that a BT keyboard does.

Display

The display is both amazing and disappointing. Browse some photos and some of them will show up in eye-popping clarity. Websites display fine. But the screen can also take on a washed-out appearance at times. I am notoriously picky in my displays, and this bothered me enough that I researched it. Analysis has shown that poor firmware calibration has lead to the compression of highlights, which mirrors what I was seeing. I am mostly used to it by now, but it’s a disappointment.

Most of the time, though, the screen is excellent. In comparison to my eInk Kindle, however, I don’t think any tablet will ever be as good for book reading. The eInk screen truly is easier on the eyes, and the reflection of overhead lights on the Nexus 7 display can be distracting at first.

I have had occasional issues with it not registering touches properly. This is always cleared up by touching the power button to put the unit to sleep, then waking it back up.

Other Hardware

There are three hardware buttons: power and volume up/down. Physically, the device fits my hand well, though I might wish it was a little lighter like my Kindle. Charging is accomplished via high-power 2A micro-USB, and there is, of course, a headphone port. There is no alert LED like my Galaxy Nexus has, and no vibration feature. The speaker is on the back, and the microphones along the left side – a position which, it appears, many Nexus 7 cases are blocking.

Battery Life

I am astonished at how good this device is battery-wise, especially compared to the battery disaster that is the Galaxy Nexus. Google claims the Nexus 7 can survive 8 hours of solid screen-on use, and I don’t doubt it. Mine’s never gotten low enough to get a solid measurement.

Wifi

The wifi works well, as far as it goes. The wifi doesn’t support 802.11n in 5GHz, which although somewhat common for devices like this, is a bit of a disappointment.

Software

The big story about the Nexus 7 is Jelly Bean. I had used Honeycomb on the Xoom, and Ice Cream Sandwich on my Galaxy Nexus, so I’m familiar with its predecessors. Let’s take a look.

Project Butter

Much has been made of Project Butter, Google’s attempt to optimize Android to improve its responsiveness and the smoothness of things like scrolling. I can say they have done quite well. This device is so smooth you don’t notice how smooth it is. It wasn’t until I had been using it for a bit that I really noticed. That’s a job well-done.

Chrome

The browser in Jelly Bean is now called Chrome. I am not sure if this is just marketing or not. It doesn’t really feel all that different from previous versions of the Android browser, and the changes have been along the lines of incremental changes Google has introduced before.

One of the very best new features happens when you touch a link that is close to other links on a page. Rather than getting a pretty much random page, Chrome pops up a partial-screen zoom box showing the part of the page near where your finger touched. With everything showing up huge, it is now easy to touch the precise link you want. Do so, and the box goes away, and your page loads. I am amazed at how much improvement this one change brings. Compared to ICS Browser, bookmarks can be brought up quicker, and the tab interface is nicer.

All is not perfect in the land of Chrome, however. It contains several regressions from the Ice Cream Sandwich browser.

I have two complaints about bookmarks. One is that previous versions of the browser would show thumbnails of sites in the bookmark viewer. This was a nice navigation aid. Chrome shows only favorites icons, if one is available, or a generic icon if not. Also, the bookmarks synced with other Android devices are called, confusingly enough, “Desktop Bookmarks” now, and require an extra tap to access.

I have had occasional trouble with Chrome not wanting to prompt for credentials for servers on my LAN that use HTTP auth.

Chrome has also removed the ICS browser’s ability to save a page, including all its elements, for offline viewing. Good for things like an airline checkin screen and such. I have no idea why Chrome removed this. I installed the Firefox Beta for Android, which also doesn’t have the offline save feature, but it does have a save to PDF feature.

Soft Keyboard

The on-screen soft keyboard in Jelly Bean is a significant regression from previous versions of Android. My biggest complaint is the lack of visual feedback for keypresses. On earlier versions of Android, when you push a key, you’ll see an image of it pop up on the screen, offset a little from the location of the key itself. In JB, all that happens is that the key itself changes colors. Not very helpful, because it is under your finger at the time. This small thing frustrates me to no end.

The keyboard in ICS introduced some nice features as well, mainly long-presses as shortcuts to other features. For instance, you can long-press a key on the top row of letters to get numerals without having to switch to the number mode. Similarly, long press the period and you get other common punctuation. The JB keyboard removed both of those features.

Thankfully, in the Market, there is an app called Ice Cream Sandwich Keyboard. It appears geared towards people running earlier versions of Android. Sadly, it is also a step up over what we have in JB.

Google Now and Voice Recognition

The other main headline feature in Jelly Bean is Google Now. The somewhat-competitor to Apple’s Siri, Google Now takes a bit of a different approach than Apple. It is said that Siri is better than Google Now at responding to queries, but Google Now is better at predicting what you want to know before you ever ask. I haven’t ever used Siri, but I would buy that explanation.

Google Now is available with a swipe up from the bottom of the screen, or with a single touch from any Home screen. Bring it up and it shows you current information about what it thinks you need to know. Examples include weather and forecast information, time to get to home or work from your current location, alerts that you need to leave soon to get to a certain place on time, flight schedules, sports scores, etc.

Google Now has been mostly a gimmick to me, but that may be because I fall outside its target demographic in significant ways. I live nowhere near a public transportation system, work at home for the most part, haven’t flown wince I’ve had the Nexus 7, don’t follow sports, and already know how long it takes to get places (and when it varies, it’s because of muddy roads or harvest — neither things that traffic services know about.)

The weather widget always seems to show the temperature from a couple of hours ago. It does show the weather in your current location. Well, mostly. I was in Newton, KS one day. I tapped on the icon for more detail. That simply took me to a Google search for “weather Newton”. Which showed me the weather for Newton, Massachusetts — 1600 miles away. Fail.

Speech recognition in JB is definitely improved. It is somewhat useful with Google Now. I like being able to simply say “set alarm for 30 minutes.” And it does it a lot quicker than I could in the interface. It’s supposed to be able to let me bring up my contacts in the same way, but it is much more likely to try turning such an attempt into a Google search than an actual display of a contact. It’s picky on the precise language used for setting an alarm too; say it slightly differently, and it’s another Google search.

JB also supports limited offline speech recognition. I say limited because it’s a bit strange. I have, for instance, a Remember the Milk widget on my home screen. It has a microphone icon to use to speak a new reminder. Tap it, and you can’t use it offline. It also has a button that brings up the on-screen keyboard. Do that, then touch the microphone on the keyboard, and you can use offline recognition. I have no idea how to explain this difference, since both are clearly using Google’s engine.

The speech recognition is indeed better, and might make it suitable for use instead of a keyboard for composing short texts and such. But it rarely produces even a sentence that I don’t have to correct in some way, even now.

Conclusion

Despite some of its shortcomings, I am very fond of the Nexus 7. It is an excellent device. And at $200-$250, it is an AMAZING device. I am truly impressed with it, and don’t regret my purchase at all.

Proof Humans Are Capable of Working Magic

Uncategorized

What an astonishing thing a book is. It’s a flat object made from a tree with flexible parts on which are imprinted lots of funny dark squiggles. But one glance at it and you’re inside the mind of another person, maybe somebody dead for thousands of years. Across the millennia, an author is speaking clearly and silently inside your head, directly to you. Writing is perhaps the greatest of human inventions, binding together people who never knew each other, citizens of distant epochs. Books break the shackles of time.

A book is proof that humans are capable of working magic.

— Carl Sagan, The Persistence of Memory

How to get started programming?

Programming

I have been asked for advice from several people recently on how to get started programming, or how to further develop a nascent interest in coding or software engineering. The people asking the questions range in age from about 10 years old to older than me. These are people that, for various reasons, are not very easily able to take computer science courses right now.

One would think that, since I’ve been doing this for somewhere around a quarter century (oh I do feel old now), that I’d be ready to offer up some great advice. And offer some suggestions I have. But I’m not convinced they’re good ones.

I have two main tensions. The first is that I, like many in the communities I tend to hang out in such as Debian’s, have a personality that leads me to take a deep dive into details of anything that holds my interest. Whether it’s Linux, Haskell, or amateur radio, I want to do more than skim the surface if I’m having fun with it. Many people are not like that. They may have a lot of fun programming in Visual Basic, not really caring that other languages are out there. Or some people are not like this yet. I feel unqualified to provide good advice to people that are different from me in that way. To put it a different way: most people don’t want to wait 4 years to be useful, and want to start out right away and get better over time (and I was the same way too.)

The second is related. I learned programming at a time when, other than BASIC, interpreted languages were not really available to me. (Yes, they were available, but not to me.) I cut my teeth on BASIC, Pascal, and C. Although I rarely use C anymore, I can still drop into it at a moment’s notice and be perfectly comfortable. I feel it was a fundamentally valuable experience, and that it would be very hard to become a great programmer without ever having lived and breathed something like C, where memory and pointers must be managed manually. Having said that, it is probably possible to become a good coder without ever having touched C.

Here, then, is an edited version of some rambly advice I sent to someone recently, where learning OOP was particularly mentioned. I would welcome your comments and suggestions. I may point people that ask to this post in the future.

For simply learning how to write code, Dive Into Python has long been a decent resource, though it may assume more experience than some have. I haven’t read them myself, but I’ve also heard good things about the How to Think Like a Computer Scientist series from Green Tea Press. They’re all available as free PDF downloads, too!

Eric S. Raymond’s The Art of Unix Programming is another work I’ve heard good things about, despite having never read it myself. A quick glance at the table of contents makes me think that even if people don’t wind up working on Unix, the lessons and philosophy should be informative.

It seems that many Computer Science programs are using Java for the core of their instruction, or even almost exclusively. Whether that is good or bad, I’m not completely sure. It certainly gets people into OOP more deeply, but I’m a “right tool for the job” kind of person. Despite the hype, OO — like everything else — isn’t the right tool for every job.

It is fine for people to dive straight into OO and become good programmers/engineers. However, I think it would be difficult to become a great programmer/engineer without ever having a solid understanding of a more low-level language, such as C in particular. I did my CS work when it was mostly based in C, and am glad for it. If someone never has to manage memory or pointers, I suspect they will be at a disadvantage in the long run for not being able to understand or work with the system at a more fundamental level. If a person knows C, plus some concepts of OO and Functional Programming (FP), it should be easy to pick up just about any other language out there.

I used to think Python was a great first language, but during the 2.x series they added so much fluff and so many special cases that I’m less enthusiastic now, though I don’t know how much of that got cleaned up in 3.x. I am not too keen on Java as a first language, because too many things that should be simple aren’t. I have a fondness for Haskell, and its close relationship to mathematics could make it a great first language — or maybe a poor one, depending on your perspective.

One other thing – I think it’s important for good programmers to have experience with all three major models of programming (procedural, OO, functional.) Even if a person winds up working mostly in one universe, knowledge of and experience with the others is important and informative and, in my experience, leads to better algorithms and architecture all around.

  • Procedural languages: Obviously C, but also Unix shell
  • OO languages: Python, Java, plenty of other fine choices
  • Functional: Lisp, Scheme, Haskell (also the only lazy and pure language on this list)

    • Having said all that, more important than a choice of book or language is experience. I have heard people suggest that it takes 10,000 hours of practice to become a superstar at something, whatever that “something” is, and I wouldn’t doubt it. Seth Godin discusses that a bit, with some criticism of the idea too.

    So that leads to the most important piece of advice: dive in to whatever your interest is. Experiment, write code, put theory into practice in a way that holds interest and excitement. People that try to do things they don’t enjoy don’t seem to stick with them as long or execute as well, and thus will never become great.

A Linux-Based RFID Thing Finder

Hardware, Technology

Sometimes I have things nicely organized. Power adapters for radios in one drawer, for cameras in the next. And sometimes… not so much. Sometimes I’m not sure if things are in the basement or the attic. It seems like technology should be able to help solve this problem, but as far as I can tell, no such solution exists yet.

So I’m planning to build one.

Here’s my general idea. Feedback, of course, is welcome.

Each item to be tracked can have an RFID tag of some sort attached to it. These tags can be read by an RFID reader at a distance of somewhere between 1ft and 1m in typical conditions. The reader could then act as a proximity alert to an object being searched for – a “you’re close” beep, for instance.

That helps, but is only part of the battle. It doesn’t help if you don’t even know which room to look in. So the second part of the plan is that the RFID reader is constantly talking to an object database. Besides the obvious association between RFID tag IDs and object descriptions, the database will also capture background reads of RFID tags. Logged with accurate timestamps, we can then conjecture that RFID reads that occurred within a few seconds of each other are probably physically nearby. If boxes have RFID tags on them, then I can probably get a reasonable idea, down to a box or two, of which box that elusive book is in. If I further put tags on certain immovable physical locations in the house, such as every few feet along shelving, then these will also be captured in the background and hopefully associated with objects nearby, giving a good physical idea of where things are.

What’s more, the simple act of looking for things using the RFID reader would help keep the proximity tables up-to-date, since it could of course log the RFID tags it sees on the way. The only discipline required to keep this info current is to periodically hover nearby storage areas when moving things around.

I like this concept a lot. That doesn’t mean it’s necessarily simple.

Implementation requirements

  • The cost of tagging an item must be less than $0.25 each. Ideally it would be $0.10 or less. We’re talking hundreds or thousands of items here, so even the $2.50 RFID tags for sale on hobbyist sites are way too expensive. RFID tags in industrial bulk quantities are needed, and cheaply.
  • Read range must be at least 1ft, and ideally 3ft, and ideally even around as many obstacles as possible. Shorter than that and it can’t even take in a whole box without pulling things out.
  • Cost kept as reasonable as possible.
  • Must be simple and unobtrusive, requiring little manual effort or discipline to maintain current data. This is the reason for RFID instead of barcodes; barcodes require much more specific action (scan the bin, scan the item) rather then just turn on the scanner and wave it around a bit.

Software side

I’m envisioning the software being split into two components. One would run on an embedded system with the RFID reader. Its job is simple transmitting of scanned RFIDs to the server, receiving instructions from the server, and generating a tone if it’s in search mode and the item being searched is nearby.

On the server lies a database. The database would contain descriptions for the objects that are tagged (so that the tag ID can be looked up). It would also contain the timestamped scan logs.

I envision a simple CGI-based frontend to it that is mobile-friendly, so a laptop, phone, tablet, etc. could be the user interface for the thing – saving the cost of a display and input device by reusing what most people already have.

This is the part I feel most qualified to work on already.

Hardware

The first question is what kind of RFID tags to use. Optimizing for cost per tag, the 800/900MHz UHF tags (EPC gen 2) seem ideal. I have found them in costs approaching $0.10 per tag when bought in rolls of 500 or 1000 Avery RFID labels. That’s reasonable.

The RFID reader is the more complicated part. UHF RFID readers are a lot more costly than their HF or LF counterparts. So far, the cheapest solution I have found started with a post about an Arduino UHF reader. It used a SolidDigi UHF reader board with UART interface for $177. That same board is also available with a USB interface at the same cost.

There is also the need for an antenna. There is a small 5dBi one rated 0-50cm for $8, or a $100 8dBi version rated 1-6m designed for wall mounting. They sell these in kit form that include power adapter, USB cables, etc. as well. The kit with the small antenna runs $192, including reader board.

Next is the compute platform. A DreamPlug might work for this at $160, though both the cost and the power consumption (5VDC 3A) are high. A Raspberry Pi seems perfect, though for whatever reason seem to be backordered by months everywhere and don’t include wifi. The Pi is $35, and the USB wifi is another $30, plus a cheap SD card, so we’re around $80 of computing. The running total of the project, then, is at least $272. Add on provisions for batteries, some sort of case, etc. and we’re probably past the $300 mark. That’s a lot cheaper than the $1000 for handheld RFID readers.

The final item is tags. Bulk tags can be found in the $100 to $200 range, making the total cost of the project $400 to $500. Higher than I’d like, but providing some valuable experience building something.

Risks

There are a few major risks to the project. First among them is read distance. If it’s not long enough, the usefulness of the project will be low. Fortunately, $100 gets a more high-gain antenna and I’d only be out the $8 if the cheaper one doesn’t pan out. But that’s something of a cold comfort, as it’s another, well, $100.

Having a bunch of RFID hardware can be used for all sorts of other interesting things, though, so it could perhaps be reused or repurposed.

Another risk is that RFID collisions wouldn’t be handled as intelligently as I’d like, meaning that the read range required to be useful would activate so many tags that collision algorithms break down. I don’t know enough about RFID collision algorithms to know if this is a serious councern.

Decisions on Listening to Music

Music, Software

A couple of days ago, I commented about my thoughts on finding a better way to listen to music, and asked for suggestions. I’ve checked out the avenues suggested, and here are my thoughts so far.

Streaming service: Spotify

Of the streaming service offerings, Spotify seems the most compelling. It has both Linux and Android clients. The Linux client is unofficial and a bit buggy, but serviceable. The service is fairly nice, and the serendipity of listening to “radio” of tracks like any track or artist I may pick is an incredible feature. It will mean a different mindset; rather than carefully choosing what I buy, I have a vast catalog at my fingertips. I’d have to give up some control, but might be better off for it.

Spotify can play local files, but sadly lacks support for FLAC that most of my collection is in. A little work with the shell, and I had a quick multi-core FLAC to MP3 conversion done. It can also identify local files and match them up with its catalog, but it does a somewhat poor job of it, despite the fact that my files are tagged by Musicbrainz. There are also a fair number of albums in my collection (from Magnatune and from local artists) that aren’t in Spotify’s catalog and probably never will be. I may wind up using git-annex or something like it to sync them between PCs.

Surprisingly, it doesn’t have any kind of web-based player available. It has a lot of features, but many of them are under-documented.

Subsonic / Supersonic

The idea of being able to stream music anywhere certainly has appeal, and the idea of streaming that music from my own machine — my own collection — is quite the appealing one. Subsonic seems to be the standard that people recommend for this. It has a web-based player that works well, as well as mobile clients for various platforms. The Android mobile client is particularly well-regarded and is probably the best one here, aside from Spotify. The playlists work well, as expected, and generally it has the appearance of a well-rounded system. There is a lot of flexibility in bitrates; maximum bitrates can be set per-user and per-client. It, of course, transcodes on the fly.

My chief gripe about Subsonic is that it has no true album/artist/genre browser. Its main browser is mostly a filesystem browser. I have used clients that show album/artist/genre panes or sortable lists, based on tags, for so long that my filesystem organization is rather different – centered around bitrate of rip, origin, etc. It is not very easy to navigate my collection in that way. The search feature can search artist and album, and this can partially make up for it. But there is simply no way to see a list of all artists in the collection.

The server is written in Java, and takes up 362MB at startup. That’s, I guess, decent for a Java server, but doesn’t make me pleased as I’d be running it on lower-end hardware.

Supersonic is a git-maintained actively synced subsonic fork which removes the license cost (the source is GPL3 anyhow so that wasn’t a big deal).

Ampache

Often mentioned in the same breath as Subsonic, this is yet another frequent suggestion for streaming your own collection. Its primary player is web-based, like Subsonic. It has full artist/genre browsers, and adds tag cloud and various other options as well – by default, it loaded the tag cloud with my genre tags, which was a nice touch. The search feature is a little less robust, as it simply searches anywhere and returns a list of all matching tracks, rather than listing matching albums and artists before going into the list of all tracks. But that is somewhat of a minor nit.

Ampache’s web-based player, liks Subsonic’s, uses Flash, but the implementation is really quite awkward. You can’t simply click a play button and have playback start. Rather, you must add things to the “playlist” (queue), a frame on the web interface. Then, you must click play in THAT frame, which launches a new window for the player and transfers its contents to it. You thus have two separate running playlists. And if you think you can just add to the playlist of the player window, think again; you can only replace it. It is simply not possible to add a track to the end of that list without losing your existing place. This makes the usefulness of the web-based player rather, well, low.

Playlist functionality in Ampache is rather odd. You can have playlists, but if you want to add a track to a saved playlist, first you have to clear you current playlist, then add the track to it, then save it to the existing playlist.

Frontends for Ampache exist in banshee and in amarok. Banshee’s is broken, and simply silently fails to do anything. Unless you look in the console, in which case you’ll see a .NET backtrace. Banshee has had these mysterious errors for me for years. The Amarok plugin is so basic that you can browse by artist but not by album, and is almost unusable. There is also a rhythmbox plugin in Debian, but it is apparently for an old version of Rhythmbox and no longer works.

The best frontend is a dedicated Ampache frontend called Viridian. It has a nice interface, provides features such as taskbar integration, and generally works pretty well. The only thing it’s bad at is playlists, and here it’s even worse than the web interface. It doesn’t support modifying the server-side playlists at all. And accessing one is an annoying “load playlist” operation, that replaces your current play queue (also called the “playlist”) with its contents by default.

Several Android clients exist for Ampache, though it seems only one has seen any updates since 2010.

mpd

This is an interesting program, as it is designed more to provide multiple points of control for a single player than it is to stream a single collection to multiple devices. Nevertheless, I tested its HTTP and icecast stream modules. (It can also stream with PulseAudio, but PulseAudio causes devious breakage on my workstation, so I refuse to bother.) This could be made to work reasonably well on my LAN using the gmpc client. There are several Android clients as well, though none of them integrate as well as Subsonic or Spotify. Most seem focused on controlling a remote player. The ones that do stream do so with some hiccups, and don’t integrate controls with the lock screen.

gmpc is a reasonable control program and, combined with mplayer, makes a decent player. It can browse the database every way I’d want to. It doesn’t let me right-click on tracks to add them to playlists, but I can use copy/paste to do so, or add them to the play queue and from there to a playlist. It’s annoying, but not completely unworkable.

But here’s the real concern. mpd has no provision whatsoever for any sort of encryption such as SSL. If I want to be listening to my music collection from on the road, I don’t really wish to open up a streaming music service for the entire Internet. Nor do I really want to mess with SSH tunnels and the like, which are cumbersome on Android (and can be in general). This is pretty much a fatal flaw to me.

Google Music

An interesting service, but ultimately one I don’t see the point for in my situation – where I already have my music on a PC that is always on. It would probably accommodate my entire collection free, but how many weeks would it take me to get it there? And how would it stay in sync? It simply doesn’t offer me any compelling advantage over streaming direct from my PC, so I don’t see much need to bother with it.

Others

I briefly considered Streeme (poor mobile support), Audiogalaxy (no Linux support), Jinzora (appears dead), and Sockso (no mobile support). I also briefly considered other streaming services such as Pandora, Slacker, rdio, etc., but based on reviews didn’t think that they were worth bothering with.

Conclusions

I’m left mainly considering Spotify and Subsonic. For right now, I’m going to try Spotify and see where that leads me, but may wind up getting back to Subsonic if I can’t find tracks I want with Spotify.

How to listen to music?

Music, Software

This seems like a simple question: how do you listen to music?

But in a way, I think I’ve fallen behind the times.

I’ve enjoyed listening to digital music for years, since well before MP3 even existed (MIDI files could be comfortably downloaded over dialup; some of you may even remember MOD files).

Anyhow, a few years ago, I digitized my entire CD collection, ripping it to FLAC and encoding to high-bitrate MP3 for storage on my 160GB iPod. Since, I’ve purchased some music from DRM-free MP3 retailers, and even FLAC files from Magnatune, but at this point I basically say that I have enough music. I have only rarely bought anything new in the last couple of years. I have used Musicbrainz Picard to enforce consistent tagging across almost my entire collection.

I am usually in front of a Linux machine. I run mt-daapd on my fileserver, so I can stream music from it to any other machine in the house. However, this has a lot of drawbacks. It is generally impossible to create or modify persistent playlists with this protocol. I can’t modify metadata. I can’t assign ratings. Though perhaps I don’t need to.

There are a lot of online services I could think of: Pandora, Spotify, Rdio, Slacker. Plus, of course, the upload your music to the cloud services such as Google and Amazon. Have people tried these? I’m hesitant to use a service where I pay a monthly fee, unless I wind up owning the music in a DRM-free fashion. And I’m a little nervous about the privacy implications of uploading a vast amount of music to the cloud.

There are some items in my collection that I am certain are not available on any of those others, but for the most part I’m willing to take what is out there if it meets my tastes. My tastes, by the way, typically run to classical and opera but also can go towards middle eastern or certain new age music (though I’m very picky about that, since I don’t care for most new age stuff I hear.) But these are huge categories; sometimes I’d like to hear some load and noisy classical (say, Beethoven’s Ninth conclusion, some Wagner, Verdi arias, etc.) And other times, something more contemplative (a Mozert concerto) or even quiet (a nice sonata) meet my mood. I have playlists for these on my iPod Classic – a bit of a problem, since I don’t use that device much anymore except in the car, and it takes a LOT of time to categorize things into these playlists. (An opera or a symphony could have parts in various styles and various levels of energy, for instance.) I keep a small manually-managed subset on my Android phone, which works fine. A recommendation engine for things like this could be useful, if it works well.

My requirements, basically: I want something that will play the same music on my Linux machines. I want to be able to have playlists kept in sync across my machines. And I don’t want a monthly fee. Ideally, the software will work on Android as well, and provide similar features there. Anything that requires Windows is a non-starter. I’ve considered NFS mounts, but that’s a bit annoying when the laptop disconnects from the network or when it’s not at home.

What are your thoughts? Ideas?

I introduced my 5-year-old and 2-year-old to startx and xmonad. They’re DELIGHTED!

Children & Computing, Family

Two years ago, Jacob (then 3) and I built his first computer together. I installed Debian on it, but never put a GUI on the thing. It’s command-line, and has provided lots of enjoyment off and on over the last couple of years. I’ve written extensively about what our boys like to do, and the delight they have at learning things on the command line.

The looks of shock I get from people when I explain, as if it’s perfectly natural, that my child has been able to log in by himself to a Linux shell since age 3, are amusing and astounding. Especially considering that it is really not that hard. Instead of learning how to run an Xbox, he’s learned how to run bash. I like that.

Lately, Jacob (now 5) hasn’t been spending much time with it. He isn’t really at a stage where he wants to push his limits too far, I think, but yet also gets bored with the familiar. So I thought it was time to introduce a GUI in a limited fashion, perhaps to let him download photos and video from his Vtech toy camera (that takes real low-res photos and videos which can be downloaded over a USB1 link). He’s familiar with the concept, at least somewhat, having seen GUIs on Terah’s computer (Gnome 2) and mine (xfce4 + xmonad).

So last night, Oliver (age 2) and I went down to the basement on a mouse-finding expedition. Sure enough, I had an old PS/2 mouse down there that would work fine. The boys both helped string it through the desk up on our play room, and were tremendously excited to see the red light underneath it when the computer came on. Barely able to contain the excitement, really. A bit like I remember being when I got my first mouse (at a bit of an older age, I suppose.)

I helped him them in as root for the very first time. (Jacob typed “root”, and I typed the password, and provided the explanation for why we were telling the computer we were “root”.) Jacob and Oliver alternated typing bits of some apt-get command lines. Then while we waited for software to download, I had to answer repeated questions of “how soon will the mouse work?” and “what does ‘install’ mean?”

Finally it was there, and I told Jacob to type startx. I intentionally did not install a display manager; more on that later. He pressed Enter, the screen went blank for about 5 seconds, and then X appeared. “Excited” can’t begin to describe how they acted. They took turns playing with the mouse. They loved how the trash can icon (I started with XFCE) showed trash IN the trash can.

But they are just learning the mouse, and there’s a lot about a typical GUI that is unfriendly to someone that isn’t yet proficient with a mouse. The close buttons are disappointingly small, things can be too easily dragged on and off the panel and menus. When I sat down to think about it, the typical GUI design does not present a very good “it always works the same” interface that would be good for a child.

And then it occurred to me: the perfect GUI for a child would be simply xmonad (a tiling window manager that can be controlled almost entirely by keyboard and has no need for mouse movements in most cases.) No desktop environment, no file manager in the root window. Just a window manager in the classic X way. Of course!

So after the boys were in bed, I installed xmonad. I gave Jacob’s account a simple .xsession that starts a terminal and xmonad.

Today, Jacob informed me that he wanted his computer to look “just like yours.” Playing right into my hands, that was! But when he excitedly typed startx, he said it wasn’t just like mine. Uh oh. Turns out he wanted the same wallpaper as my computer uses. Whew. We found it, I figured out that xli(1) loads it in the root window, and so I added a third line to .xsession. More delight unlocked!

Jacob mastered the basics of xmonad really quickly. Alt-Shift-C to close a window. Alt-Shift-Q to quit back to the “big black screen”. Alt-Shift-Enter to get a terminal window.

We launched thunar (the XFCE file manager) and plugged in his camera. He had a good deal of fun looking at photos and videos from it. But then I dropped the true highlight of the day for him: I offered to install Tuxpaint for him. That’s probably his favorite program of all time.

He watched impatiently as apt-get counted down 1m30s for tuxpaint and its libraries. Then we launched it, and he wanted to skip supper so he could keep playing Tuxpaint on “my VERY OWN COMPUTER!”

I’d been debating how to introduce GUIs for a very long time. It has not escaped my attention that children that used Commodores or TRS-80s or DOS knew a lot more about how their computers worked, on average, than those of the same age that use Windows or MacOS. I didn’t want our boys to skip an entire phase of learning how their technology works. I am pleased with this solution; they still run commands to launch things, yet get to play with more than text-based programs.

At bedtime, Jacob asked me, very seriously:

“Dad, how do I start tuxpaint again?”

“First you log in and type startx. Then you can use the mouse.”

Jacob nods, a contemplative look on his face..

“Then,” I continue, “you type tuxpaint in the terminal, and it comes right up.”

Jacob nodded very seriously a second time, as if committing this very important information to long-term memory. Then gave a single excited clap, yelled “Great!”, and dashed off.