STM32C011. Cant run sysclk from LSI.

[SHDK2000]

Im trying to run SYSCLK from LSI on a STM32C011. But it appears as if the MCU is not running. I cant see anything in the datasheet that says the clock cant be used and it can be routed fine in the clock configurator. Am I missing something in the datasheet or does the HAL not support it?

[SHDK2000]

Why I wnat to verify, that my MCU is running? Seems obvious to me, but ok. If it doesnt run, then nothing will work. Isnt that an ok reason?

I use my oscilloscope to verify MCO behaviour.

[mfgkw]

Sorry for not beeing precise enough, I wonder why you want to use LSI to feed Sysclk.

[SHDK2000]

I want to use LSI to power SYSCLK to minimize current consumption.

[Andrew Neil]

Usually the best way to minimise current consumption is to maximise use of low-power modes.

So you want  the CPU to run quickly - then it can finish sooner, and sleep longer.

[mfgkw]

Maybe you look at the wrong pin for the clock signal.
DS13867 says in 3.9:

Clock output:
– MCO and MCO2 (microcontroller clock output) provides one of the internal
clocks for external use by the application.
– LSCO (low speed clock output) provides LSI or LSE in all low-power modes.

I assume LSI is not routed to MCO.

LSCO is mentioned as alternate function on Pin13 for LQFP48.

[Andrew Neil]

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@SHDK2000 wrote:

Nothing happens with LSI.

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You mean you don't see any UART output?

That's not the same as nothing happening !

Have you used the debugger to check that your code is actually running?

How do you check for UART output? If using a terminal, it might show nothing because the baud rate is wrong...

Have you used an oscilloscope to see if anything is coming from the UART? 

Does just toggling a GPIO pin work?

[SHDK2000]

Sorry for not clarifying.

I said nothing happens because i meant NOTHING happens.

I dont get MCO out when routing SYSCLK to the output even if I ONLY use the autogenerated code with an idle while(1) main loop. It works when I use HSI, so I know its the right pin.

I dont get UART output of any kind. When I use HSI it works.

I cant toggle a pin. When I use HSI it works.

I cant use a debugger, cause I get the message "Target is not responding, retrying...". Works when I use HSI.

I tried both on the NUCLEO-C031C6 board, and a board with the STM32C011, that I made myself. I cant get any response when using LSI as SYSCLK. When I use HSI, everything works fine.

[mƎALLEm]

Start by removing the UART APIs call and check what happens on MCO

[SHDK2000]

I have mentioned already, that I cant even run an idle loop using the autogenerated code. NOTHING happens. I did also attach the ioc file.

[mƎALLEm]

I don't have that part number to test the case.

I will do it when I have on at hands.