Running STM32F4 from an Oscilator

[isaac]

Posted on May 29, 2015 at 07:17

System Clock Configuration tool is doing a great job to generate init code for STM32F405RG however it does not support external clock oscillator which is fed into OSC_IN (pin 5) only. (meaning Osc not Crystal).

I suspect that the  RCC_CR_HSEBYP bit setting does not support such hardware.Is there a code example for the required modifications into the tool generated system_stm32f4xx.c file ? #stm32f4-clock

[waclawek.jan]

Posted on May 29, 2015 at 07:51

> Is there a code example for the required modifications into the tool generated system_stm32f4xx.c file ?

Maybe there is, but what prevents you from writing your own clock startup code? As you've remarked, the difference is only in setting one bit. JW

[isaac]

Posted on May 29, 2015 at 08:02

Reassured this was tried. It still might be a hardware issue but I'm trying to ensure it's not a firmware one before running to the hardware guys ...

[waclawek.jan]

Posted on May 29, 2015 at 08:14

Hardware issue can be excluded by a single touch with a scope probe, 5 seconds of work plus half an hour to locate the oscilloscope if it does not sit on your desk... 😉

Which STM32 model exactly? Please post the content of relevant RCC registers. You try to run a simple blinkey to check, do you. JW

[waclawek.jan]

Posted on May 29, 2015 at 08:19

Oh, and 5 more seconds to check CLK_OUT is floating, using a continuity tester (ohmeter, ''beeper''...)  😉

JW

[Mark Edwards]

Posted on May 29, 2015 at 19:56

Don’t forget the half hour of tracking down the scope probe clips before giving up and using bit’s of wire.

Even if it does live on your desk.

[waclawek.jan]

Posted on May 29, 2015 at 20:06

🙂

It's the power cord in our lab. If you find the scope, it never has a power cord. It appears to be a consumable disappearing at an alarming rate, regardless of how much we buy for spare. JW