rs232 with interrupt on change pin

[ralph79]

hi all,

I know that is a very strange thing, but for an old control board, I need to have serial communication (receiving and transmitting) in a pin that doesn't have external interrupt or rda interrupt. Basically I need to have 2 serial ports (and the micro just has one in hardware, and I can't use the external interrupt pin).
So my idea is to use the interrupt on change (pin) capability for processing the data.
The micro is the PIC16F1936 and the CCS compiler is v. 5.089.

[Ttelmah]

Problem is that as configured, your 'software' channel takes longer
to receive a character, than the hardware serial. Now while it is servicing
the software RS232, other interrupts can't be serviced, so depending on the
channel timings, if more than one byte of data arrives on the hardware
port while it is servicing the software port, data will be lost.
This will also happen when the software port sends characters as well
Using 'DISABLE_INTS' means that interrupts will be disabled during
the character transmission.
Preferably 'swap' the ports. If using this approach, you always want the
software serial to handle the characters that take the least time.

[ralph79]

I can't swap the ports.
The most that I can do is lowering the bit rate from the port1 (hardware) to 19200. I can't make anything more.
I have tried to not include the disable_ints option but the result is more or less the same. My system acts like a master and slave. So its not possible to have tx2 and rx2 at same time.
By the way I have the micro at 32MHZ so that I can have time for almost everything. Its just a problem of timing/garbage/bit corruption in one soft serial.
I posted this thread because, I assumed that I was forgetting of some detail in soft interrupt.

[Ttelmah]

Yes, the key is that while you are receiving using this approach (and
transmitting if disable interrupts is used), for the whole 'character time',
you can't handle any other interrupt...

Suggestions:

Lowering the hardware rate should help.
Alternative, receive using a timer handler instead. I posted a version a while
ago:

<http://www.ccsinfo.com/forum/viewtopic.php?t=39958&highlight=software+rs232+disturbed+interrupts>

This was coded for 9600bps, but at your processor speed should work to
38400bps, by changing the timer period.

[ralph79]

I managed to put it working. I had to remove all the things that could interrupt in the middle of the reception. I had to increase the timers interrupt time so that I could give time to my "soft serial" to pick up all the bytes.