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Question about Clock speed, PWM frequency, and UART buffers for STM32F4xx

Question asked by NNNNNNNN on May 9, 2012
Latest reply on Jun 15, 2012 by jlc.jlsilicon
Like the title says I have a few questions about, all for the STM32F4xx series micro.

1. How can I set the micro to use an 8 MHz external crystal to achieve the maximum clock rate of 168 MHz. I have tried using the clock configuration excel spread sheet but I haven't gotten it to work correctly. 

2. How can I set the PWM output frequency? Right now I've only been able to get a maximum of 16KHz output. I need to get this up to 20KHz+ and out of the audible range. 

3. I have a lot of control data coming in over the UART in the form of a big array of unsigned chars. I can read in one character at a time fine, but is there any way I can read the array, encapsulated with start and end chars, into one big serial buffer then parse out the parts I need?