Software int RDA with 12f675

ghostmanzero · Joined: 01 Jan 2017 Posts: 12

Hi everyone, I'm working on a simple rf example. I want to design it as cheap as possible. rs232 communication is ok. But it looks like 12f675 doesn't support an rda interrupt. Because compiler didn't compile it.

"Error: invalid pre-processor directive" that's the error message that i got.

Is it possible to create a kind of software rda interrupt with ordinary interrupt function ? Would it work like rda ? Baud rate will be 1200 or 2400. I will just control 2 LEDs which are on the receiver by two buttons which are on the transmitter.
Can anybody help me to find a solution, please?

temtronic · Posted: Tue Jun 06, 2017 1:09 pm

Yes, you can use any I/O pin of the 12F675 as a software UART input as it has selectable Interrupt on change for all the pins, usually you'd use GP2 the 'external interrupt' pin though.
You need to remember, if using the internal oscilator , it's not too accurate, though at 1200 or 2400 baud, it should be fine.
Also software UARTs have NO HW buffering, so it's up to YOU, the programmer to handle the 'details'.
You may want to see about prices for small PICs that have a HW UART. It may be possible to find one with HW UART and more memory for less than the 12F675 !

Jay

jeremiah · Joined: 20 Jul 2010 Posts: 1349

You can also use a timer interrupt if you are able to run your PIC much faster than the baud rate.

Here is a post from TTelmah with an example. Temtronic's comments about oscillator accuracy also apply.

https://www.ccsinfo.com/forum/viewtopic.php?t=51403&highlight=uart

Ttelmah · Joined: 11 Mar 2010 Posts: 19518

Get the 12F1822.

This has a hardware UART. RX on RA5 movable to RA1.

Cheaper. About 2/3rd the price. (Microchip want to sell the newer chips rather than the older ones...).

Faster.

2* the RAM, 2* the ROM.