SPI DMA - Communication between STM32H753ZI and ESP32S

[Yusei]

Hi,

I'm trying to set up SPI communication between a STM32H753ZI (Master, using SPI2) and an ESP32-S (Slave), using the ESP32SPISlave library.

Setup:

• STM32 SPI2 pins:

  • PB10 (SCK) → ESP32 GPIO18

  • PC2 (MISO) ← ESP32 GPIO19

  • PC3 (MOSI) → ESP32 GPIO23

  • PE11 (CS) → ESP32 GPIO5

• SPI Mode 0, 8-bit, NSS controlled manually (software)

• GND is shared, 3.3V logic

• Prescaler (for Baud Rate) 256
• SYSCLK 400MHz

The STM32 sends 0x55 and expects a reply (ESP32 sends 0xAB via transfer()), but I always receive 0x00.

CS is pulled LOW just before HAL_SPI_TransmitReceive() and HIGH after. The transfer function does not block.

Question:

Why is STM32 always reading 0x00 on MISO, even though the ESP32 slave is responding with data? Any ideas or STM32-specific SPI2 issues I should check?

I don't know how I have to configure the ESP's clock, same with the STM32..

Thanks in advance!

[TDK]

Remove the ESP32 and connect MOSI to MISO on the STM32 to see if it receives what it sends. If it does, STM32 is doing its job.

Use a logic analyzer to figure out what is being sent on the line.

[Yusei]

If I connect the MOSI to MISO of the stm, I get the correct value.

I will think about buying a logic analyzer, thank you for the advice, I didn't know this device!

[TDK]

> If I connect the MOSI to MISO of the stm, I get the correct value.

Good, shows STM32 working/receiving as expected.

Since you're controlling CS manually, not much else could be to blame other than the ESP32 behavior.