Running STR91x with a a non-25MHz Oscillator - strange values from the baud rate generator

[istvan]

Posted on April 20, 2013 at 21:03

Dear Colleagues,

Actally, I couldn't get a 25Mhz crystal so I put a 24Mhz on my system, adjusting the PLL to SCU_PLLFactorsConfig(200, 25, 2) (the M,N,P parameters), so it makes it run at 96Mhz again. All is fine but my baud rate generator for UART generates odd values (like it's clock is sourced form the crystal direclty....hm). As I can tell from the Block Diagram, it's sourced from APB and the APB and  all the other clocks are set up to be based on fmclk which is sett to PLL...all should work fine, but still.... Any ideas here? #baud-rate-fr #str91x-24mhz-clock

[istvan]

Posted on April 30, 2013 at 18:32

A __main_crystal sometimes appears in the init.s and it seems to be set to 25MHz by default, changing that makes the debugger show 115176 kbit/s speed (actually I can now set the PLL to any speed, the baud rate generator seems to lock od the proper baud rate now), which is ok, but I'm still getting absolute rubbish during the communication. 

So there is communication, but it's rubbish, like when the baud rates does not match.While on my MCBSTR9 with the 25MHz crystal all works fine.... The wiring is correct, and I tried to change the MAX3232 chip but I still get the same rubbish. Any ideas?