usart receiving bad char

[drolleman]

When the usart is eceiving good chars it works flawlessly. But when the usart is receiving bad char's it works for a while the stops. I use the funtion to clear the garbage.


#ifdef UART_ON
if (RCSTA1 & 0x06)
{
output_high(pin_a3);
ch=RCREG; //empty anything that is in the buffer
ch=RCREG;
if (OERR1) {
CREN1=0;
CREN1=1;
}
}
else output_low(pin_a3);

but if the errors come at a high rate it stops receiving all together. the error funtion still is working, the pin a3 is still going up and down, but even if the data is clean the only way to get it to start receiving again is to reset the chip.

Is there a way to reset the uart? or clear other errors?

[PCM programmer]

What PIC are you using ?

[Guest]

the pic is 16f648A

[Ttelmah]

You don't show the definitions for the registers, so it is impossible to see any errors that might exist here.
However the problem is almost certainly, that toggling CREN, may toggle the OE fo this peripheral, if there is a character in the input buffer (though you clear it before hand, if it becomes set at this point). If it does so, then the TRIS bit for the receive, will become cleared, and the UART will stop being able to receive data, till this bit is set. There is an erratum for the chip regarding this (the bit is not meant to do this...). Try either setting this bit in the TRIS register after enabling the peripheral, or (if you are using standard IO), perform a dummy 'read' from this bit, which will set the bit.

Best Wishes

[Guest]

I attemped to read from the bit and did not help.

what i did next was sent 1000 char at 19.2 k, the 648a was set to 9600. i noticed that the error funtion was running continiously during the send, witch it should. then and sent 1000 char @9600 (no errors were detected) to it, and the interuput did not fire even once. then resent 1000@19.2k and errors were detected again. then reset the chip and sent the 1000 @9600 and it received it ok. then i used another pic to simulate errors. if there is 1 out of 20 errors it works ok, but if i send 1000 char's of error then the uart will not funtion again until reset.