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C6747 PSP 1.30.01 and UART baud rate calculation

Fawad Nackvi62335
Expert 1080 points
Other Parts Discussed in Thread: TL16C752C

Hello,

I am using the PSP 1.30.01 and the UART calculation for the baud rate divider could done a little better.  The code in Uart.c:

   value = (Uint32)((instHandle->deviceInfo.inputFrequency) /
                 (Uint32)((Uint32)Uart_BAUD_MULTIPLIER * (Uint32)baudRate));

    (instHandle->deviceInfo.baseAddress)->DLL = (Uint8)(value & 0xFF);
    (instHandle->deviceInfo.baseAddress)->DLH =  \
                                             (Uint8)((value & 0xFF00) >> 8);

So for my C6747 at 372 MHz (UART clock is 186MHz)  and baud rate of 115200, I get

186000000/(16x115200) = 100.  However 100 produces a baud rate of 116250 (about 0.9% out). This 1% error can be high enough to cause an issue with another TI device I am using (TL16C752C).

A better calculation could be to make the division in float and round it correctly.  This would produce a divider of 101 and the new rate would be 115099 kBaud (about 0.1% error).

In addition maybe both 16 and 13 dividers could be tried to see which comes closet to the requested data rate too.

Thanks,

Fawad