stm32f3discovery - l3gd20 gyroscope send constant values

[leszek]

Posted on September 08, 2015 at 12:16

Hello,

I have problem with l3gd20 gyroscope, which is part of stm32f3disco. I try to communicate with it using built in stm32f3 uC. I wrote my library for using SPI and this gyroscope. Theoretically SPI is working correctly, because I receive proper value of WHO_AM_I register, but when I try to read measurement registers (OUT_X_L etc.), the values of register dont change - they are constant even when I'm moving the board. They can only change when I turn off and turn on the power, but then I am reading new constant values. I was trying to run my application on three different stm32f3 disco - the results were the same. I'm doing simple configuration of l3gd20 - I write CTRL_REG1_PD | CTRL_REG1_XEN | CTRL_REG1_YEN | CTRL_REG1_ZEN to CTRL_REG1. I really don't know where is the problem - do I configure it wrong? Or is my configuration of SPI partially wrong? Below is source code of my SPI configuration. I would be grateful for your help.

void
l3gd20_conf() {

/* włącz zegary */

RCC->AHBENR |= RCC_AHBENR_GPIOAEN;

RCC->AHBENR |= RCC_AHBENR_GPIOEEN;

RCC->APB2ENR |= RCC_APB2ENR_SPI1EN;



/* ustaw alternatywne funkcje dla GPIO - SCK, MISO, MOSI */

GPIOA->MODER |= GPIO_MODER_MODER5_1 | GPIO_MODER_MODER6_1 | GPIO_MODER_MODER7_1;

GPIOA->OSPEEDR |= GPIO_OSPEEDER_OSPEEDR5 | GPIO_OSPEEDER_OSPEEDR6 | GPIO_OSPEEDER_OSPEEDR7;

GPIOA->AFR[0] |= GPIO_AFRL_AF5_5 | GPIO_AFRL_AF5_6 | GPIO_AFRL_AF5_7;


/* ustaw PE3 jako CS - GPIO output */

GPIOE->MODER |= GPIO_MODER_MODER3_0;

GPIOE->OSPEEDR |= GPIO_OSPEEDER_OSPEEDR3;

GPIOE->ODR |= GPIO_ODR_3;


/* ustaw SPI MASTER 2,25 MHz; ramka 8 bitow */

SPI1->CR1 |= SPI_CR1_SSM | SPI_CR1_SSI | SPI_CR1_MSTR |SPI_CR1_BR_1 | SPI_CR1_BR_0;

SPI1->CR2 |= SPI_CR2_FRXTH;

/* wlacz SPI */

SPI1->CR1 |= SPI_CR1_SPE;

}


void
l3gd20_send_byte(uint8_t data) {

volatile
uint8_t * 
const
ptr = (
volatile
uint8_t *)&SPI1->DR; 

while
(!(SPI1->SR & SPI_SR_TXE)); 

*ptr = data; 

}

/*

uint8_t l3gd20_transfer_byte(uint8_t mode, uint8_t addr, uint8_t data) {

uint8_t buf;


CS_LOW();

if (mode == 1) {

addr |= 0x80;

l3gd20_send_byte(addr);

l3gd20_send_byte(DUMMY_BYTE);

while (!(SPI1->SR & SPI_SR_RXNE));

buf = (uint8_t)SPI1->DR;

return buf;

} else {

l3gd20_send_byte(addr);

l3gd20_send_byte(data);

return 0;

}

CS_HIGH();

}*/

uint8_t l3gd20_transfer_byte(uint8_t val) {


/*while (!(SPI1->SR & SPI_SR_TXE));

SPI1->DR = val;

while (!(SPI1->SR & SPI_SR_RXNE));

return (uint8_t)SPI1->DR;*/

volatile
uint8_t * 
const
ptr = (
volatile
uint8_t *)&SPI1->DR; 

while
(!(SPI1->SR & SPI_SR_TXE)); 

*ptr = val; 

while
(!(SPI1->SR & SPI_SR_RXNE)); 

return
*ptr;

}


void
l3gd20_write_byte(uint8_t addr, uint8_t val) {

uint8_t d;

CS_LOW();

d = l3gd20_transfer_byte(addr);

d = l3gd20_transfer_byte(val);

CS_HIGH();

}


uint8_t l3gd20_read_byte(uint8_t addr) {

volatile
uint8_t val;

addr |= R_BIT;

CS_LOW();

val = l3gd20_transfer_byte(addr);

val = l3gd20_transfer_byte(DUMMY_BYTE);

CS_HIGH();

return
val;

}

#spi #stm32f3 #l3gd20 #drdy #stm32

[adam239955]

Posted on September 08, 2015 at 12:36

With an oscilloscope you can check the GPIO PE1 that Data Ready changes. You will have to configure CTRL_REG3 to enable the interrupt. If it is constant, the values in your gyroscope are never read.

Hope this is some help.

[leszek]

Posted on September 08, 2015 at 13:16

Unfortunatelly i haven't got an oscilloscope. But I assume that you think that I should wait fixed part of time, before I read first values. I am doing big loops beetween start configuration of SPI and sending of configuration to l3gd After configuration I also make big loop, so I think that before I read first bytes everythinh should stable and data should be ready.

It takes few minutes beetween start-up and read first byte.. And next reading are with time interval about ~3 seconds, so imo this must be sufficient interval. Initial configuration code:

for
(it = 0; it < 100000000; it++);
for
(it = 0; it < 100000000; it++);
for
(it = 0; it < 100000000; it++);
l3gd20_conf();
for
(it = 0; it < 100000000; it++);
for
(it = 0; it < 100000000; it++);
for
(it = 0; it < 100000000; it++); 
for
(it = 0; it < 100000000; it++);
l3gd20_write_byte(CTRL_REG1, CTRL_REG1_PD | CTRL_REG1_XEN | CTRL_REG1_YEN | CTRL_REG1_ZEN);
for
(it = 0; it < 100000000; it++);
for
(it = 0; it < 100000000; it++); 
for
(it = 0; it < 100000000; it++);
for
(it = 0; it < 100000000; it++);

[leszek]

Posted on September 08, 2015 at 16:19

I also found out that when I'm checking status register new vaules are only available at first time, so that's why I'm reading constant data, but I dont understand why this is situation occurs, because the device is configured to continuos data updating