Challenge: I need a pi to talk to an arduino without resetting the arduino. I have shields on the arduino that prevent me from using a resistor to bridge 5v and gnd. The shield also blocks my access to RX/TX pins so I can't go use a hardware serial connection with a voltage divider to the pi GPIO pins. Using a daemon on the pi I want to open a connection to the arduino and then keep it open, passing messages back and forth between the arduino and my program.
Method: On the pi side I've got PEAR installed with System_Daemon and php_serial.class.php. I use a mysql db as a 2-way buffer.
Problem: The daemon doesn't appear to be receiving anything from the arduino. I know the daemon can read and write with mysql.
My daemon code so far: http://pastebin.com/hM9dJNsE
The error messages:
err: No stty availible, unable to run. [l:58]
warning: Specified serial port is not valid [l:141]
warning: Unable to set the baud rate : the device is either not set or opened [l:234]
warning: Unable to set parity : the device is either not set or opened [l:288]
warning: Unable to set length of a character : the device is either not set or opened [l:336]
warning: Unable to set the length of a stop bit : the device is either not set or opened [l:377]
warning: Unable to set flow control mode : the device is either not set or opened [l:422]
warning: The device must be set before to be open [l:167]
stty definitely exists on the pi and can be run as user root or pi, so I don't know why I'm getting error #1dd.
Why is this happening? Is there a better way? Has anyone got a working example?