External clock other than 8 MHz for STM324L Discovery

jp1 · ‎2015-10-18

Posted on October 19, 2015 at 07:04

Hi,

We would like to use the STM32L4 Discovery board with an external clock other than 8 MHz. SysClock = HSE. We plan to do this by disconnecting MCO from the ST-Link STM32F PA8 pin.

Will we be able to continue to use the ST-Link for flashing and debugging the STM32L MCU on the STM32L4 Discovery board? Any other concerns we need to watch out for?

Thx

#msi-hse-demo-stm32l4-discovery #stm32l4-discovery-mco-8-mhz-hse

Tesla DeLorean · ‎2015-10-19

Posted on October 19, 2015 at 17:04

It's just a convenient crystal based source, you can remove it an supply what ever other source clock you want. Check the data manual, but I'd expect it to support 4-26 MHz crystals, and oscillator sources to 50 MHz. Use bypass mode when not directly using a crystal.

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jp1 · ‎2015-10-21

Posted on October 21, 2015 at 09:42

Our attempt to use an external 8 MHz clock source instead of MCO has mixed results. We replaced MSI as the clock source with HSE in ''main.c'' and ''iddmeasusre.c'' (attached).

The demo compiles with no errors but shows the welcome screen on the glass LCD instead of displaying the IDD value for each of RUN, SLEEP, LP Run, LP Sleep modes.

Are we missing something? Any help will be appreciated.

________________

Attachments :

iddmeasure.c : https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006HzjJ&d=%2Fa%2F0X0000000bSN%2FsOftmQnj5OXBfYZqIh.K2yTEFMUvfwh8mjzNFx6vPB0&asPdf=false

main.c : https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006I01f&d=%2Fa%2F0X0000000bSL%2Fvxn.T7_R_ugpbqbMUJpnYc0iJfiPsRkF7ADfIc1wXoE&asPdf=false

Tesla DeLorean · ‎2015-10-21

Posted on October 21, 2015 at 15:23

The demo compiles with no errors

But understand that means the compiler sees no syntax errors, not that the code is logically correct.

What frequency are you trying to supply? And what's the nature of the clock signal?

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jp1 · ‎2015-10-21

Posted on October 21, 2015 at 19:14

Clive,

We decided to test the code with the MCO from the ST-Link MCU. Its a square wave - 8 MHz.

jp1 · ‎2015-10-22

Posted on October 23, 2015 at 04:28

The square wave has a 3.3V amplitude. We checked all the settings..still does not work.