PIC18F14K22 UART

[boulder]

I already tried this method, it works. However, Interrupt method does not work well.

[PCM programmer]

Try using a standard circular buffer, such as the Ex_Sisr.c example,
instead of your #int_rda routine.

[boulder]

I tried Ex_Sisr.c example, and it acts the same way. However, there is a good news that it works fine with my test code and example code if I use the other baudrates instead of 115200. Could anyone explain it to me? My project requests 115200 baudrate.

Thanks.

[PCM programmer]

Earlier, I did a count of the number of instruction cycles needed to
process the interrupt, and compared it to the time required to receive
or transmit a byte. I found that the isr execution time was lower,
so it should work. But, I could have overlooked something.
Easy answer:

Increase your crystal frequency to 7.3728 MHz (2x your existing freq).
This may fix the problem. Change the #use delay statement and
use the HS fuse for this frequency.

[boulder]

I think that it's too late to change crystal. Is it okay to enable 4xPLL in #fuse?

[boulder]

I enabled PLL in #fuses and changed baudrate to 28800 in #use rs232 since frequency is 4 times faster, now uart interrupt is working very well with the actual 115200 baudrate.

[PCM programmer]

You shouldn't use incorrect rates for the baud rate. Change the #use
delay() statement so it fits the new 4x oscillator frequency. The
compiler will setup everything correctly, provided that you set the
#use delay() to match the actual speed of the oscillator. In the case
of a 3.6864 MHz crystal with a 4x PLL, the oscillator freq is 14.74564 MHz.
See below:

[boulder]

PCM,
Your are right about this. However, the compiler does not take care timing. If I want to delay 100ms, I have to write 'delay_ms(400)'.

Thanks!!

[boulder]

I was wrong. The compiler does take care of timing after change frequency in #use delay(). Thanks.