Saturday, January 16, 2010

My first steps with the Arduino

I recently received the arduino I ordered on Makershed. Actually, I took a starter kit to play with this small piece of hardware. The board has an ATMEGA328 uproc (8-bit) with few I/Os to play with.

They offer a nice tiny sdk to write your code/compile and upload. I've nothing to say, it's working great, they did a good job, however, since I am an emacs aficionados (and I'm not a Java fan), I wanted do the process manually.

The first was to analyze a bit was was given in the arduino (software) package. The file being in arduino-0017/hardware/cores/arduino/Makefile gives you the makefile to compile your programs. We can already notice that it does not work out of the box and that you've to modify it.

Here are my modifications:

INSTALL_DIR = $(HOME)/arduino-0017
PORT = /dev/ttyUSB0

AVR_TOOLS_PATH = /usr/bin
SRC = $(ARDUINO)/pins_arduino.c $(ARDUINO)/wiring.c \
$(ARDUINO)/wiring_analog.c $(ARDUINO)/wiring_digital.c \
$(ARDUINO)/wiring_pulse.c \

AVRDUDE_FLAGS = -V -F -C $(INSTALL_DIR)/hardware/tools/avrdude.conf \

Well, you notice that one file somehow disappeared in SRC. I simply removed it and it seems to be working. Also, the AVR_TOOLS_PATH was pointing on a wrong directory.

Now, for compiling your stuff, a simple make must be enough.

The next step was the upload that was a big deal for me. Actually, it was working with the Java interface, but not with avrdude. Actually, I was using the following command, because I saw it somewhere:

avrdude -V -F -C ~/arduino-0017/hardware/tools/avrdude.conf -p m328p -P /dev/ttyUSB0 -c stk500 -b 19200 -U flash:w:applet/Fading.hex -vvvvvv

Well, I got the following message:

avrdude: Send: 0 [30] [20]
avrdude: Send: 0 [30] [20]
avrdude: Send: 0 [30] [20]
avrdude: ser_recv(): programmer is not responding
avrdude: stk500_recv(): programmer is not responding

So WTF (Huh, btw, I entered twice avrdude avrdude [...], it segfaults after trying one :)) ? How so it's working with the Java App, but not with the avrdude ? As a wise guy said once "one week of trial and error can save up to half an hour of reading documentation", well, actually I could have read the Arduino troubleshooting section, but...

My idea was to sniff the what's going on /dev/ttyUSB0 when using the Java IDE and compare it with the avrdude command. To sniff it, I found jpnevulator as being usefull.

When running it, ./jpnevulator --read --tty /dev/ttyUSB0, turned out that I was getting the "programmer is not responding" error message even in the Java IDE :), this meant that the Java IDE was calling avrdude somehow (since this is an avrdude error message).

Cool, I downloaded the Java files from their svn and started to grep on these. In arduino/app/src/processing/app/debug/ I found something interesting:

if (verbose || Preferences.getBoolean("upload.verbose")) {
for(int i = 0; i < commandArray.length; i++) {
System.out.print(commandArray[i] + " ");

So, since I did not want to recompile all the files (lazy ?), I just wanted to set this boolean upload.verbose to true. Turns out that the preferences are read from a file ~/.arduino/preferences.txt, so you just have to add "upload.verbose=true" somewhere in there.

Now we run the Java program again and we the nice working avrdude command. We can use it directly after resetting the device (by pushing the button or directly sending a reset signal).

The command it now:

/usr/bin/avrdude -V -F -C ~/arduino-0017/hardware/tools/avrdude.conf -p atmega168 -P /dev/ttyUSB0 -c stk500v1 -b 57600 -U flash:w:applet/Fading.hex

Basically, the speed was wrong. Again, don't forget to push the reset button before shipping the code on the board

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