Hello. I'm using Hi-tech PICC pro and PIC12F629. I want to make a simple usart communication subroutine: I've set Timer0 to make an interrupt every 250 miliseconds. In that interrupt I want to check whether there's an incoming byte from RS232. If there isn't - exit the interrupt and resume normal work. If there is - read the byte in a variable, and start a dialog subroutine. The thing I can't make is the interrupt - how do I check if there's an incoming byte, when I use the soft usart?

Can't help you with C, but a 250mS timer routine would be useless, you could (and would) miss loads of data in the 250mS.

If you want interrupt driven routines then best to choose a PIC with a hardware UART, otherwise you need to check for the presence of a start bit VERY much more often, depending on baud rate.

A software option would require an interrupt as the start bit begins, which could be done if the PIC supports interrupt from a pin change - this is usually available on PortB (interrupt on change on portb). Check the datasheet, see what the 12F629 has got.

Hmm, OK. Today I thinked about it and figured out a way how to make it without an interrupt. Thank you for the help anyway