Bit Banging input to output on PIC16F876A

[mister_e]

The real question is: What is the highest HPWM frequency I can accurately reproduce on the PORTB.6 output assuming a 20MHZ Crystal?
Thanks in advance!

Well, i really depend of the accuracy you can/want to deal with. PICMultiCalc says you can produce up to 2.5 MHz @ 20MHz.. but <4 bit resolution... only 8 duty steps

To do so, you'll need to configure the CCP registers manually.

[Bruce]

Melanie,

I would love to see an example of how this works. It would be really nice for sending IR serial
data modulated at 38-40kHz.

[Melanie]

Give me a couple of days Bruce to find some spare time and throw an example together - I'll post it here... watch this space...

[mister_e]

7 days a week, 24 hours a day, you only work 120 hours a week... so you still have spare time huh?

I see what's you're cooking. I've used something like that in the past... before i lost everything on my hard drive

I remember that i also modified SEROUT routine... and it also remember me something that Darrel already did here... i'll search for it now.

[Bruce]

I've tried what Melanie mentioned, but could never get it to work properly when changing
Vref with another I/O-pin.

[mister_e]

Probably where...

... and almost no software overhead...

came from.

2 diodes, 1 resistor build a cheap AND gate... without code overhead.

<hr>
EDIT: smells like the comparator input change, then within the ISR you perform the AND function.

[Dave]

Bronurstomp, Why even involve hardware as the ccp module inside the pic can do the work for you. Just set the period and pwm of the ccp module at 38khz. and set the ccpl value to 50 % or 0%. I have been doing this for the last 5 years in the development of the tire pressure lf transmissions at 125 khz...

Dave Purola,
N8NTA