No signal on mco1

[teijo]

Posted on December 13, 2012 at 11:00

hello, I'm using stm32f207(LQFP64) mcu in custom made hw. Compilers are gnu arm-eabi-gcc and arm-eabi-gdb for debugging. main fuctions for mcu are: - output 27mhz clock MCO1(PA8) - listen interrupts at EXTI15_10_IRQ(PB15). This is active low - Mcu uses internal RC oscilator and is configured to 108MHz clock This sw is tested in the previous hw and it's working fine. But now i'm trying to test newer version of hw and I run into very strange problems. 1. there is no clock in the MCO1 pin. 2. when I debug the code, ext irq occurs even if there is no pulses in the irq line(I've checked it with a scope). (The code it goes to Reset_Handler). So i made test code that tricles test pin (GPIOx) and feeds clock to MCO pin. Test pin changes state fine, but I don't see the clock signal at the (PA8) MCO output. I tested this code to anoter hw(other project same mcu(LQFP100)) and there are correct signal from MCO pin.

any help will be appreciated. br, Teijo

[frankmeyer9]

Posted on December 13, 2012 at 11:28

To me, that sounds like a hardware problem.

Have you checked the supply voltage for stability and ripple ? Possible EMI problems ? Does it work if you reduce the core clock frequency (would probably require sw changes) ?

[teijo]

Posted on December 14, 2012 at 08:27

I tested another board(same design) and manage to get signal to MCO1. Definitely hw issue.

Teijo