Confusion Between HSE Clock Value in the Schematics on STM32L4R9I-EVAL Board and user manual

[ZAYN]

Hello Community,

I have been working on CAN for two days, and I haven't been able to figure out the baud rate issue I'm facing. I'm using the HSE as the clock source with a value of 25MHz, as mentioned in the UM2248 document (I'm using the STM32L4R9I-EVAL evaluation board). I've configured the baud rate to 500kbps, but it doesn't work. I suspect the microcontroller switches to the HSI clock at 16MHz. When I reconfigure the baud rate to 500kbps with a 16MHz clock, it works fine.

However, when I check the schematics of the board, I see that the X2 crystal is at 16MHz. This creates confusion between the clock value defined in the UM2248 document and the board schematics. Could you please explain why there is a difference between the X2 value in the UM2248 document and the schematics of the evaluation board?

Additionally, could you share the schematics for the STM32L4R9I-EVAL MB1313-B-03 board? I couldn't find this exact version online.

Thank you very much for your help.

Schamtic link : https://www.st.com/resource/en/schematic_pack/mb1313-l4r9i-b02_schematic.pdf

User manual of the STM32L4R9AI (Please se section Clock references ) : https://www.st.com/resource/en/user_manual/um2248-evaluation-board-with-stm32l4r9ai-mcu-stmicroelectronics.pdf

[1f333]

is it actually possible to see the crystal? any marks? partnumber?

[SofLit · Accepted solution]

Hello @ZAYN and welcome to the community,

I will escalate your question internally. I agree there is a discrepancy between the schematics and the user manual. 

I will get back to you as soon as I have an answer (Internal ticket number 199349). The answer could be delayed due to Christmas.

Meanwhile, you can also use MCO pin to output the the HSE signal and check.

[Tesla DeLorean]

BoM

X2 NX3225GA-16MHz-EXS00A-CG04815

https://www.st.com/en/evaluation-tools/stm32l4r9i-eval.html#cad-resources

HSE_VALUE in stm32l4xx_hal_conf.h, 16 MHz

https://github.com/STMicroelectronics/STM32CubeL4/blob/master/Projects/STM32L4R9I-EVAL/Examples/CRC/CRC_Example/Inc/stm32l4xx_hal_conf.h#L91

A lot of other EVAL boards have 25 MHz, and use it for Ethernet

Confirm the part as placed, perhaps scope PA8 / MCO

[ZAYN]

Hello Community,

Thank you very much for your help.

I measured the clock signal at the quartz using an oscilloscope, and I confirmed it's 16 MHz.

I understand that there might be multiple versions of the evaluation board, which could explain the discrepancy with the 25 MHz value mentioned in the user manual.

I will double-check the version of the quartz on the hardware and get back to you.

Thank you again, and I wish you all a Happy New Year!