USART SmartCard Clock

[rasminoj]

Posted on September 13, 2011 at 15:24

I am using STM32F107VC with system clock set to 72MHz. I want to set USART3 clock to 4MHz in smart card mode without changing APB1 clock (which is 36 MHz, and all software relied on this value). I have to use USART3 because smart card ic rooted to mcu pins which can only be USART3 in pcb. 

thanks in advance.

#usart-smart-card

[Tesla DeLorean]

Posted on September 14, 2011 at 16:42

USART3 is only rated up to 2.25 Mbps, unless I'm mistaken.

What baud rate do you actually want to achieve?

If you need to hit specific frequencies you will need enough design flexibility to change the primary oscillator, PLL, and bus dividers to achieve your goals. Most of us tend to write software sufficiently transparently that we can change frequencies at a single point, and have the application/drivers compute appropriate downstream peripheral/clock settings.