PIC18F1220 RA4 using PULSIN ?

[sinoteq]

Hi
This problem have been up before in the forum. http://www.picbasic.co.uk/forum/showthread.php?t=11236 I bet the reason that RA4 does not work is because the Schmitt trigger buffer on that pin. The easy explanation is that your R/C receiver is a 3V device and you run your PIC on 5V. You can solve this in many different ways depending on what you feel like doing. The easiest is a pull up resistor on the RA4 input to boost the voltage. This will however feed a higher voltage into the R/C receiver and that might be a problem. Or you change the voltage to 3V.

Where in the datasheet is this? Under DC Characteristics datasheet page 250 under 22.3

By the way I think the datasheet for PORTA has a big misstake in it.

[Del Tapparo]

Yes indeed! That is my problem. RA4 is a Schmitt trigger input and my Rx puts out 3V pulses with the PIC running at 5V. Thank you very much for saving me a bunch more time and headache.

Unfortunately, a pull-up won't fix it, so time for a hardware design change.

[Charles Linquis]

When I have to do level shifting I find that a 74HCTxx gate does a good job. Power it from 5V.

[sinoteq]

What do you have on RA1? If it is empty make a solder bridge and you have your hardware change.

[Del Tapparo]

Problem was resolved by reassigning I/O. Good tips though. Thanks to all. I learned something (always a good thing).