Our makerspace got a donation of a bunch of Galileo gen2 boards from Intel (image from Mwilde2 on Wikimedia commons).
The Galileo line has been discontinued, so there's no support and no community, but in theory they're fairly interesting boards. You can use a Galileo in two ways: you can treat it like an Arduino, after using the Arduino IDE to download a Galileo hardware definition since they're not Atmega chips. They even have Arduino-format headers so you can plug in an Arduino shield. That works okay (once you figure out that you need to download the Galileo v2 hardware definitions, not the regular Galileo). But they run Linux under the hood, so you can also use them as a single-board Linux computer.
The first question is how to talk to the board. The documentation is terrible, and web searches aren't much help because these boards were never terribly popular. Worse, the v1 boards seem to have been more widely adopted than the v2 boards, so a lot of what you find on the web doesn't apply to v2. For instance, the v1 required a special serial cable that used a headphone jack as its connector.
Some of the Intel documentation talks about how you can load a special Arduino sketch that then disables the Arduino bootloader and instead lets you use the USB cable as a serial monitor. That made me nervous: once you load that sketch, Arduino mode no longer works until you run a command on Linux to start it up again. So if the sketch doesn't work, you may have no way to talk to the Galileo. Given the state of the documentation I'd already struggled with for Arduino mode, it didn't sound like a good gamble. I thought a real serial cable sounded like a better option.
Of course, the Galileo documentation doesn't tell you what needs to plug in where for a serial cable. The board does have a standard FTDI 6-pin header on the board next to the ethernet jack, and the labels on the pins seemed to correspond to the standard pinout on my Adafruit FTDI Friend: Gnd, CTS, VCC, TX, RX, RTS. So I tried that first, using GNU screen to connect to it from Linux just like I would a Raspberry Pi with a serial cable:
screen /dev/ttyUSB0 115200
Powered up the Galileo and sure enough, I got boot messages and was able to log in as root with no password. It annoyingly forces orange text on a black background, making it especially hard to read on a light-background terminal, but hey, it's a start.
Later I tried a Raspberry Pi serial cable, with just RX (green), TX (white) and Gnd (black) -- don't use the red VCC wire since the Galileo is already getting power from its own power brick -- and that worked too. The Galileo doesn't actually need CTS or RTS. So that's good: two easy ways to talk to the board without buying specialized hardware. Funny they didn't bother to mention it in the docs.
Blinking an LED from the Command Line
Once connected, how do you do anything? Most of the Intel tutorials on Linux are useless, devoting most of their space to things like how to run Putty on Windows and no space at all to how to talk to pins. But I finally found a discussion thread with a Python example for Galileo. That's not immediately helpful since the built-in Linux doesn't have python installed (nor gcc, natch). Fortunately, the Python example used files in /sys rather than a dedicated Python library; we can access /sys files just as well from the shell.
Of course, the first task is to blink an LED on pin 13. That
apparently corresponds to GPIO 7 (what are the other arduino/GPIO
correspondences? I haven't found a reference for that yet.) So you
need to export that pin (which creates /sys/class/gpio/gpio7
and set its direction to
out. But that's not enough: the
pin still doesn't turn on when you
echo 1 > /sys/class/gpio/gpio7/value. Why not?
I don't know, but the Python script exports three other pins --
46, 30, and 31 -- and echoes 0 to 30 and 31. (It does this without
first setting their directions to
out, and if you try
that, you'll get an error, so I'm not convinced the Python script
presented as the "Correct answer" would actually have worked. Be warned.)
Anyway, I ended up with these shell lines as preparation before the Galileo can actually blink:
# echo 7 >/sys/class/gpio/export # echo out > /sys/class/gpio/gpio7/direction # echo 46 >/sys/class/gpio/export # echo 30 >/sys/class/gpio/export # echo 31 >/sys/class/gpio/export # echo out > /sys/class/gpio/gpio30/direction # echo out > /sys/class/gpio/gpio31/direction # echo 0 > /sys/class/gpio/gpio30/value # echo 0 > /sys/class/gpio/gpio31/value
And now, finally, you can control the LED on pin 13 (GPIO 7):
# echo 1 > /sys/class/gpio/gpio7/value # echo 0 > /sys/class/gpio/gpio7/valueor run a blink loop:
# while /bin/true; do > echo 1 > /sys/class/gpio/gpio7/value > sleep 1 > echo 0 > /sys/class/gpio/gpio7/value > sleep 1 > done
Searching Fruitlessly for a "Real" Linux Image
All the Galileo documentation is emphatic that you should download a Linux distro and burn it to an SD card rather than using the Yocto that comes preinstalled. The preinstalled Linux apparently has no persistent storage, so not only does it not save your Linux programs, it doesn't even remember the current Arduino sketch. And it has no programming languages and only a rudimentary busybox shell. So finding and downloading a Linux distro was the next step.
Unfortunately, that mostly led to dead ends. All the official Intel docs describe different download filenames, and they all point to generic download pages that no longer include any of the filenames mentioned. Apparently Intel changed the name for its Galileo images frequently and never updated its documentation.
After forty-five minutes of searching and clicking around, I eventually found my way to Intel® IoT Developer Kit Installer Files, which includes sizable downloads with names like
- iss-iot-linux_12-09-16.tar.bz2 (324.07 MB),
- intel-iot-yocto.tar.xz (147.53 MB),
- intel-iot-wrs-pulsar-64.tar.xz (283.86 MB),
- intel-iot-wrs-32.tar.xz (386.16 MB), and
- intel-iot-ubuntu.tar.xz (209.44 MB)
From the size, I suspect those are all Linux images. But what are they and how do they differ? Do any of them still have working repositories? Which ones come with Python, with gcc, with GPIO support, with useful development libraries? Do any of them get security updates?
As far as I can tell, the only way to tell is to download each image, burn it to a card, boot from it, then explore the filesystem trying to figure out what distro it is and how to try updating it.
But by this time I'd wasted three hours and gotten no further than the shell commands to blink a single LED, and I ran out of enthusiasm. I mean, I could spend five more hours on this, try several of the Linux images, and see which one works best. Or I could spend $10 on a Raspberry Pi Zero W that has abundant documentation, libraries, books, and community howtos. Plus wi-fi, bluetooth and HDMI, none of which the Galileo has.
Arduino and Linux Living Together
So that's as far as I've gone. But I do want to note one useful thing I stumbled upon while searching for information about Linux distributions:
Starting Arduino sketch from Linux terminal shows how to run an Arduino sketch (assuming it's already compiled) from Linux:
sketch.elf /dev/ttyGS0 &
It's a fairly cool option to have. Maybe one of these days, I'll pick
one of the many available distros and try it.
[ 13:54 Mar 10, 2018 More hardware | permalink to this entry | comments ]