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Running SPI at 2MHz

Question asked by ianmd on May 15, 2013
Latest reply on May 16, 2013 by knik
I've got an STM32F407 with main clock set to 168MHz and am communicating with a slave device over SPI2. The SPI on the slave can work up to 2MHz and I would like to get as close to this as I can.

As far as I can tell, the SPI2 clock has to be a power-of-two divisor of the APB1 which in turn is a power-of-two divisor of the main clock. The closest I can get is therefore approx 1.3MHz.

Counter intuitively I'm coming to the conclusion that to communicate at 2MHz I need to slow the system clock down to 128MHz. Firstly, is this right, or am I missing something? Secondly, does changing the system clock speed open up a can of worms that I need to be aware of? (I'm also using USB FS so presumably that would be affected).