Loading library on boot

[FriedCircuits]

Hi,

I wanted to see if you have come across a problem when you start a python program that uses DS18B20 on boot.

I have a crontab that is set to on reboot to start my python program.

The problem is when it init the library it fails. But if I run it manually with sudo at the command line it works fine.

it fails on sensor=DS18B20()

I can't see the error when it runs from cron so I have no idea what is happening.

Any ideas?

Thanks.

Edit: Sometimes I get this File "/home/pi/piminer/ds18b20/init.py", line 87, in _get_sensor return path.join(DS18B20.BASE_DIRECTORY, DS18B20.SLAVE_PREFIX + self._id, DS18B20.SLAVE_FILE) TypeError: cannot concatenate 'str' and 'NoneType' objects

[FriedCircuits]

I was able to capture the error output when run as cron

Traceback (most recent call last): File "/home/pi/piminer/PiMiner.py", line 6, in from PiMinerDisplay import PiMinerDisplay File "/home/pi/piminer/PiMinerDisplay.py", line 3, in from PiMinerInfo import PiMinerInfo File "/home/pi/piminer/PiMinerInfo.py", line 17, in class PiMinerInfo: File "/home/pi/piminer/PiMinerInfo.py", line 43, in PiMinerInfo sensor = DS18B20() File "/home/pi/piminer/ds18b20/init.py", line 63, in init self._sensor = self._get_sensor() File "/home/pi/piminer/ds18b20/init.py", line 80, in _get_sensor sensors = self.get_available_sensors() File "/home/pi/piminer/ds18b20/init.py", line 47, in get_available_sensors for sensor in listdir(cls.BASE_DIRECTORY): OSError: [Errno 2] No such file or directory: '/sys/bus/w1/devices'

[FriedCircuits]

For future reference, seems like something to do with cron which can do odd things. So going to look for another way to start it on boot as root.

[timofurrer]

I never had such problems. To be honest, I've never tried to start DS18B20 from a cronjob. For your case a cronjob is anyway not the best way to go. Instead of cronjob use a init script. Place something like this in your /etc/init.d:

!/bin/sh

### BEGIN INIT INFO
# Provides: DAEMON_NAME
# Required-Start: $remote_fs $syslog
# Required-Stop: $remote_fs $syslog
# Default-Start: 2 3 4 5
# Default-Stop: 0 1 6
# Short-Description: DESCRIPTION
# Description: DESCRIPTION
### END INIT INFO

DIR=/path/to/your/daemon
DAEMON=$DIR/daemonscript.py
DAEMON_NAME=MYDAEMON

# This next line determines what user the script runs as.
# Root generally not recommended but necessary if you are using the Raspberry Pi GPIO from Python.
DAEMON_USER=root

# The process ID of the script when it runs is stored here:
PIDFILE=/var/run/$DAEMON_NAME.pid

. /lib/lsb/init-functions

do_start () {
  log_daemon_msg "Starting system $DAEMON_NAME daemon"
  start-stop-daemon --start --background --pidfile $PIDFILE --make-pidfile --user $DAEMON_USER --chuid $DAEMON_USER --startas $DAEMON
  log_end_msg $?
}
do_stop () {
  log_daemon_msg "Stopping system $DAEMON_NAME daemon"
  start-stop-daemon --stop --pidfile $PIDFILE --retry 10
  log_end_msg $?
}

case "$1" in
  start|stop)
    do_${1}
    ;;

  restart|reload|force-reload)
    do_stop
    do_start
    ;;

  status)
    status_of_proc "$DAEMON_NAME" "$DAEMON" && exit 0 || exit $?
    ;;

  *)
    echo "Usage: /etc/init.d/$DAEMON_NAME {start|stop|restart|status}"
    exit 1
  ;;
esac

exit 0

I hope I could help! :beers:

[FriedCircuits]

Just wanted to let you know the init scripts works great.