I am using the internal oscillator (FOSC = 7.37 Mhz) of the dsPIC33EV256GM102. I have a 1602 LCD connected to the PIC via 4 data, and enable, RW, and RS control lines.
I write initialization commands to the LCD and then two lines of text. That works fine.
After 2 minutes and 10 seconds the enable line quickly pulses high-low causing something to be written to the LCD. It happens again in another 2:10 and then again, repeatably.
All my program does right now is initialize the LCD, write two lines of text and go directly into a while(1).
I have tried setting the LCD enable low on every iteration of the While. I have tried latching the enable low before going into the While. I have moved the enable to another pin but the pulse still occurs on that pin. If I remove the enable line after writing the data, the problem goes away.
Any thoughts what might cause this kind of behavior or what additional troubleshooting steps I might take?
I am using pin 24 labeled RPI45/PWM1L2/CTPLS/RB13 for the enable but I have also tried pin 23 labeled RPI44/PWM1H2/RB12. I am not executing any code related to peripheral pin select yet.
When I download the program via the Pickit3, for the first POR while the Pickit3 is still in the circuit, there is some spurious text written to the LCD. So I have to disconnect the Pickkit3 and do another POR before the two line of text are written correctly without any unwanted additional data writes.
In conclusion there are two issues really or perhaps they are related?