SPI1 Almost working but no MOSI?

[boris2]

Posted on September 11, 2014 at 19:35

I'm trying to get SPI1 up and running with STM32F4 as a master.

This was the source code / tutorial. The only changes are: MOSI is on pin PB5 instead of PA6 in the example and CS is on PA4 instead of PE7. Using a scope I see the clock, the CS but no MOSI. Any thoughts? These are my init_SPI1, SPI1_send and SPI1test functions:

void init_SPI1(void){
GPIO_InitTypeDef GPIO_InitStruct;
SPI_InitTypeDef SPI_InitStruct;
// enable clock for used IO pins
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);
/* configure pins used by SPI1
* PA5 = SCK
* PA6 = MISO
* PB5 = MOSI
*/
GPIO_InitStruct.GPIO_Pin = GPIO_Pin_6 | GPIO_Pin_5;
GPIO_InitStruct.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStruct.GPIO_OType = GPIO_OType_PP;
GPIO_InitStruct.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_NOPULL;
GPIO_Init(GPIOA, &GPIO_InitStruct);
// connect SPI1 pins SCK, MISO to SPI alternate function
GPIO_PinAFConfig(GPIOA, GPIO_PinSource5, GPIO_AF_SPI1);
GPIO_PinAFConfig(GPIOA, GPIO_PinSource6, GPIO_AF_SPI1);
GPIO_InitStruct.GPIO_Pin = GPIO_Pin_5;
GPIO_InitStruct.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStruct.GPIO_OType = GPIO_OType_PP;
GPIO_InitStruct.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_NOPULL;
GPIO_Init(GPIOB, &GPIO_InitStruct);
// connect SPI1 pins MOSI to SPI alternate function
GPIO_PinAFConfig(GPIOB, GPIO_PinSource5, GPIO_AF_SPI1);
// enable clock for used IO pins
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB, ENABLE);
/* Configure the chip select pin
in this case we will use PA4 */
GPIO_InitStruct.GPIO_Pin = GPIO_Pin_4;
GPIO_InitStruct.GPIO_Mode = GPIO_Mode_OUT;
GPIO_InitStruct.GPIO_OType = GPIO_OType_PP;
GPIO_InitStruct.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_UP;
GPIO_Init(GPIOA, &GPIO_InitStruct);
GPIOA->BSRRL |= GPIO_Pin_4; // set PA4 high
// enable peripheral clock
RCC_APB2PeriphClockCmd(RCC_APB2Periph_SPI1, ENABLE);
/* configure SPI1 in Mode 0 
* CPOL = 0 --> clock is low when idle
* CPHA = 0 --> data is sampled at the first edge
*/
SPI_InitStruct.SPI_Direction = SPI_Direction_2Lines_FullDuplex; // set to full duplex mode, seperate MOSI and MISO lines
SPI_InitStruct.SPI_Mode = SPI_Mode_Master; // transmit in master mode, NSS pin has to be always high
SPI_InitStruct.SPI_DataSize = SPI_DataSize_8b; // one packet of data is 8 bits wide
SPI_InitStruct.SPI_CPOL = SPI_CPOL_Low; // clock is low when idle
SPI_InitStruct.SPI_CPHA = SPI_CPHA_1Edge; // data sampled at first edge
SPI_InitStruct.SPI_NSS = SPI_NSS_Soft | SPI_NSSInternalSoft_Set; // set the NSS management to internal and pull internal NSS high
SPI_InitStruct.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_16; // SPI frequency is APB2 frequency / 16
SPI_InitStruct.SPI_FirstBit = SPI_FirstBit_MSB;// data is transmitted MSB first
SPI_Init(SPI1, &SPI_InitStruct); 
SPI_Cmd(SPI1, ENABLE); // enable SPI1
GPIOA->BSRRH |= GPIO_Pin_4; // set PA4 (CS) low
SPI1_send(0x6A); // USER_CTRL (Write)
SPI1_send(0x10); // Disable I2C, enable SPI
GPIOA->BSRRL |= GPIO_Pin_4; // set PA4 (CS) high
}
/* This funtion is used to transmit and receive data 
* with SPI1
* data --> data to be transmitted
* returns received value
*/
uint8_t SPI1_send(uint8_t data){
SPI1->DR = data; // write data to be transmitted to the SPI data register
while( !(SPI1->SR & SPI_I2S_FLAG_TXE) ); // wait until transmit complete
while( !(SPI1->SR & SPI_I2S_FLAG_RXNE) ); // wait until receive complete
while( SPI1->SR & SPI_I2S_FLAG_BSY ); // wait until SPI is not busy anymore
return SPI1->DR; // return received data from SPI data register
}
uint8_t SPI1test(){
uint8_t received_val;
GPIOA->BSRRH |= GPIO_Pin_4; // set PA4 (CS) low
SPI1_send(0xF5); // WhoAmI 0x75 (MSB=1 -> READ)
received_val = SPI1_send(0x00); // transmit dummy byte and receive data
GPIOA->BSRRL |= GPIO_Pin_4; // set PA4 (CS) high
return received_val; 
}

[boris2]

Posted on September 11, 2014 at 20:31

Figured out the problem.

I needed to enable the GPIOB clock BEFORE configuring GPIOB5 pin.RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB, ENABLE);