|
LDmicro Forum - HOW TO: Change USART Baud Rate |
|||
|
|
|
(you are viewing a thread; or go back to list of threads)
HOW TO: Change USART Baud Rate (by Ihor Nehrutsa)
(no subject) (by MGP)
The question is, how can we use 9600b on a 4MHZ (PIC)system, LDmicro gives a warning when compiling.
Changing the UART baudrate in the program is not a good idea if you not know what you are doing.
(no subject) (by Ihor Nehrutsa)
There is a direct relationship between the baud rate and Fosc.
Thus, you can: or change the baud rate or change the Fosc. A good idea is always to know what you are doing. ;) Autodetect baud rate needs some time.
(no subject) (by MGP)
I wonder which values he has used in his LCD program, it seems that you can't use 9600b with the internal oscillator.
But his program runs very good on 9600b I never had any problems with the LCD. https://github.com/LDmicro/LDm...CD-based-on-HD44780-controller
(no subject) (by Ihor Nehrutsa)
to MGP
I think MCU on LCD board and MCU on your board work at the 4 MHz internal oscillators. And USART baud rate set as "9600 bps" on both MCU's. In fact, the baud rate is 8900 bps on both MCU's with -7% error. Try to measure the fact transmit frequency on both MCU's with the oscilloscope.
(no subject) (by MGP)
My testboard is a pic16F876a on 20MHz 9600b and it works always without exceptions.
But if it runs on 8900b it's OK, my question is answered. Thx
(no subject) (by Ziggy)
A bit more on Baud rates and ATmega processors ( I know nothing about PICs)...
It is possible to based on a reference frequency adjust a variable which controls the free running onboard clock to be a bit more precise than the factory supplied configuration. I use an STK500 and AVRstudio 4 ( yes old and familiar ). This combination offers a utility which calculates the required value to adjust the clock. How to use this calibration value within LD micro if at all possible?
Post a reply to this comment:
|
|
|