Add the SetupCommPort() function to the serial.c file and
make sure to add the prototype to the serial.h file.
The baud rate values are set according to the following
formula;
SPBRG = (Fosc / (64 * BaudRate))-1
Fosc for the PicWiser is the value of the crystal which is
14,745,600. The calculated values for SPBRG are shown in the
second column for the 4 baud rate shown in the first column.
|
Fosc |
14745600 |
|
|
|
|
|
|
Desired Baud Rate |
SPBRG |
Actual Baud Rate |
|
9600 |
23 |
9600 |
|
19200 |
11 |
19200 |
|
57600 |
3 |
57600 |
|
115200 |
1 |
115200 |
The last column shows the actual baud rate based on the
SPBRG values and as you can see the error between the actual
and desired is 0. That is why the 14.7456 Mhz crystal is used.
Note that if we used the highest oscillator value of 20 Mhz
supported by the PIC16F876 the higher baud rate would not be
available.
|
Fosc |
20000000 |
|
|
|
|
|
|
|
|
|
|
Desired Baud Rate |
SPBRG |
int(SPBRG) |
Actual Baud Rate |
Error |
|
9600 |
31.5520833 |
31 |
9765.625 |
1.73% |
|
19200 |
15.2760417 |
15 |
19531.25 |
1.73% |
|
57600 |
4.42534722 |
4 |
62500 |
8.51% |
|
115200 |
1.71267361 |
1 |
156250 |
35.63% |
