MCU is not recognized as USB storage device

[Sophi]

Hi all - I'm new to the STM ecosystem and I've been stuck on an STM32H743/ Micropython issue.

My (custom) board can upload Micropython firmware via both SWD and DFU. So DM/ DP work.

VCC measures 3.21V, maybe a little low, maybe just my DMM.

I'm not able to get this board to communicate over TX/ RX or see the board as a USB device. 

The STM32H743 does not need series resistors on DP/DM and it has an internal pullup on DP. 

I built a new Micropython firmware with (AFAIK) the correct settings/ pins for USB in mpconfigboard.h

-Do I need to configure the internal pullup? And how? 

-What am I missing?

TL;Dr custom board w STM32, what does it need to run microPython?

[Pavel A.]

> I'm not able to get this board to communicate over TX/ RX 

Over which TX/RX? Is there a UART besides USB?

[Sophi]

Thanks Pavel. The STM32H743 has an internal UART at PD5 and PD6.

Using a USB to UART cable I am not able to reach the chip. My computer sees the cable, but not the chip.

Separately, I believe the USB pins are working since I can reach the board over DFU.

[Pavel A.]

PD5 and PD6 correspond to USART2. Cannot tell whether these pins are free to use for USART2, because the board is custom.

[FBL]

Hi @Sophi 

You don't need to configure the internal pullup since it is already integrated in the chip. Also, you mentioned your settings/ pins for USB are detailed in mpconfigboard.h and you did not attach the file to the thread. So far, you should provide more details so that we can help you!

[Sophi]

Hello,

I am still not able to get this board to show up as a MSC or communicate over UART.

Micropython is loaded into 0x08000000 and this address is verified with STM32CubeProgrammer.

I can use STM32CubeProgrammer only over ST-Link (SWD) or DFU. I'm not able to reach the chip's UART2 by TTL cable or Putty. 

I've attached mpconfigboard.h configuration file with what I hoped was correct USB and UART settings.

The external crystal is 12 MHz. Power to the STM32H743 is 3.21V

Thanks in advance!

[FBL]

Hi @Sophi 

You need to share more details about your configuration. So far, try a simple application over UART with another STM32. You need to figure out if your configuration is properly set up first. I assume this cube firmware example would be helpful with your mass storage example STM32CubeH7/Projects/STM32H743I-EVAL/Applications/USB_Device/MSC_Standalone at master · STMicroelectronics/STM32CubeH7 · GitHub