PIC hanging on Serin

[Dave]

onioni, using your scope, what is the level at the PIC rx pin when the system is in an idle mode (no data being sent)

[onioni]

Hi Dave,

I am running the 3.3V TX output through 2 inverters then to the RX pin of the PIC, so the PIC RX pin is seeing +5V when nothing is being sent.

onioni

[Dave]

onioni, That sounds good to me. Looking at the scope, is the timing correct for the baudrate? Try sending repeatedly the character "w" I beleive which should what looks a square wave. See if the time interval for the HIGH and the LOW are the same. If there is a difference this may be due to a slewrate problem with the inverters.

[onioni]

I checked the waveforms on the scope and the are identical except the one from the inverter is 5V instead of 3.3V. No differences due to slew rate to speak of. I have read on this forum that it is important to read the PIC datasheet, well I just learned a hard lesson. By properly setting the CMCON0 register to allow digital I/O, the program worked like a charm. I found this out after switching the 3.3V input-output with those of the hyperterminal. The HT was then hanging instead of the 3.3V chip. I will read the datasheet more closely next time. I appreciate you taking the time to troubleshoot with me.

onioni