Posted on June 08, 2016 at 13:09Hi all,
I am trying to read the onboard Gyro on STM32F4 discovery board. As mentioned in datasheets, Gyro(L3GD20) is conneted to SPI 5. I have configured everything, but I am not able to generate the required clock on SCK pin.
SPI 5 SCK,MISO,MOSI and CS pins are - PF7,PF8,PF9,PC1 as per schematic.
Because of this I thnik, I am not able to recive byte from SPI on my UART.
Pls help...
Thanks ...
void L3GD_CS_init(void)
{
RCC->AHB1ENR |= (RCC_AHB1ENR_GPIOCEN);
GPIOC->MODER |= 0x00000004; //PC1 as O/P
GPIOC->OSPEEDR |= 0x00;
//GPIOC->PUPDR |= 0x00000004; //Pull up PC1
//L3GD20_CS_HIGH;
}
void Spi_pins_set(void)
{
//PF6, PF7,PF8,PF9 as NSS,SCK,MISO,MOSI...refer to schmeatic for L3GD20 to SPI 5 as AF
//PC1 as CS pin for L3GD20...schematic
RCC->AHB1ENR |= (RCC_AHB1ENR_GPIOFEN);
GPIOF->MODER |= 0x000A8000;
GPIOF->OTYPER |= ((uint16_t)0x0000);
GPIOF->OSPEEDR |= 0x000A8000;
//GPIOF->PUPDR |= 0x00;
GPIOF->AFR[0] |= 0x50000000;
GPIOF->AFR[1] |= 0x00000055; //AF5 in AFR
}
void Spi_init(void)
{
//APB2 has clock 2x slower than processor speed, in my case I have 168MHz core clock, APB2 has 84MHz
//APB2 communication bus has 84MHz
//And because minimal prescaler for SPI is 2, max frequency is 42MHz
//SPI Clock = APBx / prescaler = 84MHz / 2 = 42MHz
//By default, prescaler 32 is used:
//SPI Clock = APBx / prescaler = 84MHz / 32 = 2.62MHz
/* Enable SPI clock */
RCC->APB2ENR |= RCC_APB2ENR_SPI5EN;
/* Disable first */
SPI5->CR1 &= ~SPI_CR1_SPE;
SPI5->CR1 |= SPI_CR1_BR_0 | SPI_CR1_BR_2 | SPI_CR1_MSTR; //Mode 0 SPI_CR1_LSBFIRST | SPI_CR1_SSM | SPI_CR1_SSI
/* Enable SPI */
SPI5->CR1 |= SPI_CR1_SPE;
}
uint8_t L3GD20_ReadSPI(uint8_t address)
{
uint8_t data;
L3GD20_CS_LOW;
/* Send address with read command */
SPI_Send_byte(SPI5, address | 0x80);
/* Read data */
data = SPI_Send_byte(SPI5, 0xFF);
//L3GD20_CS_HIGH;
return data;
}
int main(void)
{
uint8_t ch=0;
int i=0;
SystemInit();
usart1_set();
usart1_init();
Spi_init();
Spi_pins_set();
led_init();
L3GD_CS_init();
while(1)
{
ch = L3GD20_ReadSPI(L3GD20_REG_WHO_AM_I); //in L3GD20.h file
USART1_send_char(ch);
USART1_send_char(0x0D);
for(i=0;i<5000000;i++);
}
}
#discovery #l3gd20 #stm32f429 #spi #gyroscope
