Posted on December 02, 2012 at 09:44
I am writing some code to enable SPI to use the accelerometer. But when I enable the GPIOA clock in RCC_AHB1ENR it bricks the board and I have to use the BOOT pin to reset it. Here is the piece of code that makes it brick.
RCC->AHB1ENR |= RCC_AHB1ENR_GPIOAEN | RCC_AHB1ENR_GPIOEEN;
But when I change this line of code to:
RCC->AHB1ENR |= RCC_AHB1ENR_GPIOEEN;
It does not brick the board anymore. I checked theRCC_AHB1ENR_GPIOAEN define and it has the value 0x00000001 which is the right mask.
Why does it not like it when I enable the GPIOA clock?
Here is the entire program that I have written so far.
//Accelerometer
#include <
stdio.h
>
#include ''STM32F4xx.h''
#include ''LED.h''
#define CS_HIGH() GPIOE->BSRRL |= (1<<
3
)
#define CS_LOW() GPIOE->BSRRH |= (1<<
3
)
void SPI_init(void);
void acc_init(void);
unsigned char SPI_send(unsigned char data);
void acc_cmd(unsigned char cmd, unsigned char addr);
void acc_write(unsigned char data, unsigned char addr);
unsigned char acc_read(unsigned char addr);
unsigned char get_x_axis(void);
unsigned char get_y_axis(void);
unsigned char get_z_axis(void);
void delay(void);
int main(void)
{
LED_Init();
SPI_init();
while(1)
{
LED_On(1);
delay();
LED_Off(1);
delay();
}
}
unsigned char SPI_send(unsigned char data)
{
SPI1->DR = data;
while(SPI1->SR & SPI_SR_BSY);
return SPI1->DR;
}
void acc_write(unsigned char data, unsigned char addr)
{
}
unsigned char acc_read(unsigned char addr)
{
unsigned char data = 0;
return data;
}
void SPI_init(void)
{
/*********PINOUT*************
SCK = PA5
MOSI = PA7
MISO = PA6
CS = PE3
INT1 = PE0
INT2 = PE1
*****************************/
//Enable GPIO Clock
RCC->AHB1ENR |= RCC_AHB1ENR_GPIOAEN|RCC_AHB1ENR_GPIOEEN;
//Enable pins as output or input
GPIOA->MODER |= GPIO_MODER_MODER5_1|GPIO_MODER_MODER7_1;
GPIOE->MODER |= GPIO_MODER_MODER3_0;
//GPIO pin speed
GPIOA->OSPEEDR |= GPIO_OSPEEDER_OSPEEDR5_0|GPIO_OSPEEDER_OSPEEDR6_0|GPIO_OSPEEDER_OSPEEDR7_0; //25Mhz gpio
GPIOE->OSPEEDR |= GPIO_OSPEEDER_OSPEEDR0_0|GPIO_OSPEEDER_OSPEEDR1_0|GPIO_OSPEEDER_OSPEEDR3_0; //25Mhz gpio
//Pull up configuration
GPIOA->PUPDR |= GPIO_PUPDR_PUPDR6_0; //1 = pull down 0 = pull up default is pull up/down disabled
GPIOE->PUPDR |= GPIO_PUPDR_PUPDR0_0|GPIO_PUPDR_PUPDR1_0;
//Enable SPI Clock
RCC->APB2ENR |= RCC_APB2ENR_SPI1EN;
//Enable Alternate Function on SPI pins and INT Pins
GPIOA->AFR[1] |= 0x55500000;
//Configure SPI for master mode and Fpclk/64
SPI1->CR1 |= SPI_CR1_SPE|SPI_CR1_MSTR|SPI_CR1_BR_0;
}
void delay(void)
{
unsigned long i = 0;
for(i=0; i<5000000; i++)
{
}
}
#gpioa-clock
