Re: RB4 on the EBB

#21480
Windell Oskay
Keymaster

IIRC, the otherwise unused I/O pins are tristated at turn-on, and have floating values that can fluctuate, which is what you are seeing.  To use one as an output, you’ll need to set it to be an output first, and then set what value you want it to have.  

We use one of the other I/O pins (B3) as the digital output to control the Eggbot engraver attachment, and have found that it’s typically at ~2V at turn-on.  If you’d like to see how it works, open up the Eggbot software (eggbot.py) within the Inkscape Extensions folder, and look through the code.  The command to initialize B3, and set it to high output is as follows:
PD,B,3,0 # Set pin D3 direction (output)
PO,B,3,1 # Set pin D3 value (high)
To set it low again, 
PO,B,3,0 
This isn’t so different from the pin direction and pin value commands that one uses in Arduino.  However, they are sent as serial commands to the EBB, rather than being compiled into the firmware.