Starting a script after the CPU Linino boot

Just add the script to the /etc/rc.local file

The stdout and stderr get redirected to a log file in /tmp (ramdisk)

My rc.local on the Arduino Yun now looks as follows:

touch /tmp/begin
wifi-live-or-reset
boot-complete-notify
sleep 5s
cd /mnt/sda1/arduino/Yafa
./main.py 1> /tmp/Yafa.log 2>&1 &
touch /tmp/end
exit 0

ftp using Linino CPU and Python

I started with ftp-ing directly from the MCU using Curl.
Obviously this isn't very optimal given the Yun architecture.

I changed this so that the Linino gets the Temperature (or other measurements) from the MCU and then the Linino CPU will do the ftp-ing. Using Python this is very straightforward.

The only tricky part is that the ftp expects a file, but I don't want to put the data in a file. Luckily there exists a StringIO class that can take care of that. The code becomes something like:

import StringIO
from ftplib import FTP

myFileIO = StringIO.StringIO()

myFileIO.write(now_str)
myFileIO.write(",")
myFileIO.write(temp)
myFileIO.seek(0)
ftp=FTP("ftp.homebrew.be")
ftp.login(User,Pass)
ftp.cwd("www.homebrew.be/Yafa")
ftp.storlines("STOR dat.csv",myFileIO)
ftp.close()
myFileIO.close()

Use APPE instead of STOR if you want to append to the file.

Bridge Communication - part 5

My part4 was maybe too optimistic. It seems some people still have problems with long strings over the Bridge. A fix was found (http://forum.arduino.cc/index.php?topic=196091.msg1517378#msg1517378)

Until an official release do:

• Using SSH or YunSerialTerminal, connect to the linux side of the yun.
• Edit file /usr/bin/run-bridge, changing "python bridge.py" with "python -u bridge.py" (ie: add a "-u" to the command line)
• Edit file /usr/bin/kill-bridge, again changing "python bridge.py" with "python -u bridge.py" (ie: add a "-u" to the command line)
• Type kill-bridge and re-run your sketch

Good to knows - 4

Using the watchdog to reset the mcu if something goes wrong:

See

#include 

void setup ()
{
  Serial.begin (115200);
  Serial.println ("Restarted.");
  wdt_enable (WDTO_1S);  // reset after one second, if no "pat the dog" received
 }  // end of setup

void loop ()
{
  Serial.println ("Entered loop ...");
  wdt_reset ();  // give me another second to do stuff (pat the dog)
  while (true) ;   // oops, went into a loop
}  // end of loop

This code comes from http://forum.arduino.cc/index.php?topic=128717.msg968831#msg968831

Obviously this can be used to trigger a restart when you detect an error (if error --> while(1){})

Good to knows - 3

Converting between double/floats and strings:


avr-gcc's dtostre and dtostrf

http://www.nongnu.org/avr-libc/user-manual/group__avr__stdlib.html#g6c140bdd3b9bd740a1490137317caa44