PGA900: UART works only with 1MHz processor clock

Part Number: PGA900

I have a problem with PGA900 UART. It is not working with CPU clock frequencies other than 1MHz.
Is this normal or maybe I do something improperly?
In code example for PGA900 ( there are a few sets of UART settings for different clock frequencies. But in the datasheet there is a formula
BAUD_RATE = round( 250000 / (Desired baud rate) ) – 1
It seems to be for 1MHz.
UART is working pretty well with 1MHz CPU clock, but when I try to switch clock to 2MHz or 4MHz (and change baud divider respectively), I find it not working. I'd like to use 4MHz clock in order to realize better digital filtering.

1 Reply

  • Hi Alexander,

    I the example firmware that can be found on the TI Website please find and open the pga900_uart.h file.

    Here you can see multiple settings for the UART baud rate calculated based on different clock frequencies.

    in general, the formula for the Baud Rate Divisor is as below:

    Baud Rate Divider = ((1/(4*Baud Rate))*CPU_CLK))-1 ,

    where CPU_CLK is the MCU (M0) frequency in Hz and Baud Rate is the desired baud.

    Also make sure that the MCU is set to the correct clock frequency before selecting the UART baud and enabling the interface.