Cannot get SPI3 to work on STM32F722

[EnzoPB]

Hello,

I am using a drone FC (Flywoo F722 PRO V2), that uses a STM32F722RET6. On the board, there is a Winbond W25Q128FV flash chip wired to the SPI3 bus on the MCU (MISO PC11, MOSI PB5, SCK PC10) with CS on PC13.
I can't get this SPI bus to work, neither using libs (SPIMemory, Adafruit SPIFlash, SerialFlash) or even using a minimal SPI code:

#include <SPI.h>

#define CS_PIN PC13

#define SPI_MISO PC11
#define SPI_MOSI PB5
#define SPI_SCK PC10

SPIClass SPI_3(SPI_MOSI, SPI_MISO, SPI_SCK);

void setup() {
  Serial.begin(115200);
  while(!Serial);
  
  pinMode(CS_PIN, OUTPUT);
  digitalWrite(CS_PIN, HIGH);
 
  SPI_3.begin();
  
  delay(100);

  digitalWrite(CS_PIN, LOW);
  delay(10);
  
  SPI_3.transfer(0x9F); // read JEDEC ID
  uint8_t manufacturer = SPI_3.transfer(0x00);
  uint8_t memType = SPI_3.transfer(0x00);
  uint8_t capacity = SPI_3.transfer(0x00);
  
  digitalWrite(CS_PIN, HIGH);

  Serial.println(manufacturer, HEX);
  Serial.println(memType, HEX);
  Serial.println(capacity, HEX);
}

void loop() {}

SPI.transfer always returns what it is sending (SPI.transfer(0x01) will return 0x01), and when inspecting the bus with an oscilloscope, the CS pin it being turned LOW/HIGH correctly, but MISO, MOSI, and CLK stays at 0V.
I know the chip and the MCU hardware works, because I can write and read from the flash using Betaflight (the firmware that was on the board originally)

Is there something that I'm missing? Thanks!

[fpistm]

Hi @EnzoPB
In fact PB5 can be used for 2 SPI instance:

Arduino_Core_STM32/variants/STM32F7xx/F722R(C-E)T_F730R8T_F732RET/PeripheralPins.c

Lines 236 to 237 in e531ea8

	{PB_5, SPI1, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_PULLUP, GPIO_AF5_SPI1)},
	{PB_5_ALT1, SPI3, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_PULLUP, GPIO_AF6_SPI3)},

So simply change to:
#define SPI_MOSI PB5_ALT1

Like this the SPI3 is used for PB5 and aligned with PC10/PC11

[EnzoPB]

This worked. Thanks!

[fpistm]

Welcome