How to free NUCLEO STM32 board pins for FMC interface use

[LFerr.8]

I want to interface a Nucleo-H743ZI2 board (MB1364E) with a memory chip using STM32's FMC.

In order to do this I need to free up the following 4 pins, to be used by the morpho connector:

PE1, currently yellow user LED, needed for FMC_NBL1.

PD8, currently ST_LINK_RX , needed for FMC_D13.

PD9, currently ST_LINK_TX, needed for FMC_D14.

PD10, currently USB_OTG_FS_PWR_EN, needed for FMC_D15.

(Current use verified through STM32CubeIDE)

I am following the schematics below (MB1364):

https://www.st.com/content/ccc/resource/technical/layouts_and_diagrams/schematic_pack/group1/79/99/be/65/3c/76/40/d6/MB1364-H743ZI-C01_Schematic/files/MB1364-H743ZI-C01_Schematic.pdf/jcr:content/translations/en.MB1364-H743ZI-C01_Schematic.pdf

And the user manual for MB1364 found here:

https://www.st.com/en/evaluation-tools/nucleo-h743zi.html#documentation

PE1:

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So, pin PE1, according to the schematics can be disconnected by removing R71. I have verified that PE1 connects to R71 using a multimeter, and the schematics/manual show no solder bridge to disconnect the LED, so the first one I consider solved by removing the resistor R71.

PD10:

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I do not know the purpose of USB_OTG_FS_PWR_EN, however I believe it is related to CN13 USB, which I do not need. Page 28 of the manual shows PD10 connected to SB77, with SB77 on by default, and flipping it to off should enable morpho connector use. I have verified there is continuity with SB77 and SB77 is on by default, so the solution here would be to remove SB77.

PD8 and PD9:

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PD8 and PD9 are used for USART3 communication which I do not need. Pins PD8 and PD9 default's configuration, according to page 27 of the manual, is SB5 and SB6 ON, and SB7 and SB4 off. To use PD8 and PD9 with the morpho connector, I should flip these solder bridges (from ON to OFF and vice-versa). However, my board from factory comes with SB4, SB5 and SB7 off, and only SB6 on. Furthermore, I've checked with a multimeter and I can't find continuity between PD8/PD9 and any of these solder bridges.

On the same page (page 27 of the manual), in the text description, it says "Flying wires have to be connected between PD8/PD9 (USART3 available on SB19/SB12)". I've checked and found that PD8/PD9 have continuity with SB19/SB12.

Finally, the schematics document shows PD8/PD9 connected to SB82/SB81, which I have confirmed also with the multimeter.

I am at a loss for what solder bridges to set on/off in order to free up PD8/PD9.

[waclawek.jan]

IMO follow your instinct and - according to your description - the schematics.

For historical reasons, the "original" Nucleo144 MB1137/UM1974 was available also with the 'H743, and that's where SB5/6/7/4 come, through copypaste into UM2407/MB1364.

JW

PS. I wonder why the schematics is titled "NUCLEO 144 H7 LEGACY"...

@Amel NASRI​ , can please the discrepancies in UM2407 chapter 6.6.5 Virtual COM port (VCP): LPUART/USART (i.e. SB5/6/4/7 copypasted from UM1974) be clarified? I would also strongly recommend to add a chapter to both UM1974 and UM2407, pointing out the existence of "the other" 'H743 Nucleo and referring to "the other" UM+board number.

[LFerr.8]

Thank you. I would not expect things to just be copy pasted without being checked for errors before publication.

A clarification by ST would be much appreciated.

[Amel NASRI]

Hi @Community member​ ,

I created an internal ticket to share your proposals.

As you & @Luís Ferreira​ have identified it, required configuration for solder bridges needs to be fixed in "Virtual COM port (VCP): LPUART/USART" section of UM2407. It is also required to add SB81/SB82 to the table "Solder bridge and jumper configuration".

Internal ticket number: 133434 (This is an internal tracking number and is not accessible or usable by customers).

-Amel

[waclawek.jan]

Thanks, Amel.

Jan

[LFerr.8]

I have looked at the Altium design files and concluded that SB19 and SB12 should be turned off, in order to free PD8 and PD9, respectively, for FMC use.