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181 lines (155 loc) · 5.59 KB
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Copy pathmma.c
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181 lines (155 loc) · 5.59 KB
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#include <stdio.h>
#include <stm32f4xx.h>
#include <stm32f4xx_rcc.h>
#include <stm32f4xx_gpio.h>
#include "misc.h"
#include "systick.h"
#include "mma.h"
void mma_init(void) {
RCC->APB1ENR |= RCC_APB1ENR_I2C1EN; // enable I2C1
//gpio_pin_init(GPIOB, 6 /* B6 is SCL */, 2 /* AF mode */, 1 /* open drain output */, 1 /* 25 MHz */, 0 /* no pull up or pull down */);
//gpio_pin_init(GPIOB, 7 /* B7 is SDA */, 2 /* AF mode */, 1 /* open drain output */, 1 /* 25 MHz */, 0 /* no pull up or pull down */);
//gpio_pin_af(GPIOB, 6, 4 /* AF 4 for I2C1 */);
//gpio_pin_af(GPIOB, 7, 4 /* AF 4 for I2C1 */);
// XXX untested GPIO init! (was above code)
GPIO_InitTypeDef GPIO_InitStructure;
// PB5 is connected to AVDD; pull high to enable MMA device
GPIOB->BSRRH = GPIO_Pin_5; // PB5 low to start with
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_5;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_2MHz;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
GPIO_Init(GPIOB, &GPIO_InitStructure);
// PB6=SCL, PB7=SDA
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6 | GPIO_Pin_7;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_OType = GPIO_OType_OD;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_25MHz;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
GPIO_Init(GPIOB, &GPIO_InitStructure);
// alternate functions for SCL and SDA
GPIO_PinAFConfig(GPIOB, GPIO_PinSource6, GPIO_AF_I2C1);
GPIO_PinAFConfig(GPIOB, GPIO_PinSource7, GPIO_AF_I2C1);
// get clock speeds
RCC_ClocksTypeDef rcc_clocks;
RCC_GetClocksFreq(&rcc_clocks);
// disable the I2C peripheral before we configure it
I2C1->CR1 &= ~I2C_CR1_PE;
// program peripheral input clock
I2C1->CR2 = 4; // no interrupts; 4 MHz (hopefully!) (could go up to 42MHz)
// configure clock control reg
uint32_t freq = rcc_clocks.PCLK1_Frequency / (100000 << 1); // want 100kHz, this is the formula for freq
I2C1->CCR = freq; // standard mode (speed), freq calculated as above
// configure rise time reg
I2C1->TRISE = (rcc_clocks.PCLK1_Frequency / 1000000) + 1; // formula for trise, gives maximum rise time
// enable the I2C peripheral
I2C1->CR1 |= I2C_CR1_PE;
// wait 20ms, then turn on AVDD, then wait 20ms again; this seems to work, but maybe can decrease delays
// doesn't work for soft reboot; 50ms doesn't work either...
sys_tick_delay_ms(20);
GPIOB->BSRRL = GPIO_Pin_5;
sys_tick_delay_ms(20);
// set START bit in CR1 to generate a start cond!
}
static uint32_t i2c_get_sr(void) {
// must read SR1 first, then SR2, as the read can clear some flags
uint32_t sr1 = I2C1->SR1;
uint32_t sr2 = I2C1->SR2;
return (sr2 << 16) | sr1;
}
void mma_restart(uint8_t addr, int write) {
// send start condition
I2C1->CR1 |= I2C_CR1_START;
// wait for BUSY, MSL and SB --> Slave has acknowledged start condition
uint32_t timeout = 1000000;
while ((i2c_get_sr() & 0x00030001) != 0x00030001) {
if (--timeout == 0) {
printf("timeout in mma_restart\n");
return;
}
}
if (write) {
// send address and write bit
I2C1->DR = (addr << 1) | 0;
// wait for BUSY, MSL, ADDR, TXE and TRA
timeout = 1000000;
while ((i2c_get_sr() & 0x00070082) != 0x00070082) {
if (--timeout == 0) {
printf("timeout in mma_restart write\n");
return;
}
}
} else {
// send address and read bit
I2C1->DR = (addr << 1) | 1;
// wait for BUSY, MSL and ADDR flags
timeout = 1000000;
while ((i2c_get_sr() & 0x00030002) != 0x00030002) {
if (--timeout == 0) {
printf("timeout in mma_restart read\n");
return;
}
}
}
}
void mma_start(uint8_t addr, int write) {
// wait until I2C is not busy
uint32_t timeout = 1000000;
while (I2C1->SR2 & I2C_SR2_BUSY) {
if (--timeout == 0) {
printf("timeout in mma_start\n");
return;
}
}
// do rest of start
mma_restart(addr, write);
}
void mma_send_byte(uint8_t data) {
// send byte
I2C1->DR = data;
// wait for TRA, BUSY, MSL, TXE and BTF (byte transmitted)
uint32_t timeout = 1000000;
while ((i2c_get_sr() & 0x00070084) != 0x00070084) {
if (--timeout == 0) {
printf("timeout in mma_send_byte\n");
return;
}
}
}
uint8_t mma_read_ack(void) {
// enable ACK of received byte
I2C1->CR1 |= I2C_CR1_ACK;
// wait for BUSY, MSL and RXNE (byte received)
uint32_t timeout = 1000000;
while ((i2c_get_sr() & 0x00030040) != 0x00030040) {
if (--timeout == 0) {
printf("timeout in mma_read_ack\n");
break;
}
}
// read and return data
uint8_t data = I2C1->DR;
return data;
}
uint8_t mma_read_nack(void) {
// disable ACK of received byte (to indicate end of receiving)
I2C1->CR1 &= (uint16_t)~((uint16_t)I2C_CR1_ACK);
// last byte should apparently also generate a stop condition
I2C1->CR1 |= I2C_CR1_STOP;
// wait for BUSY, MSL and RXNE (byte received)
uint32_t timeout = 1000000;
while ((i2c_get_sr() & 0x00030040) != 0x00030040) {
if (--timeout == 0) {
printf("timeout in mma_read_nack\n");
break;
}
}
// read and return data
uint8_t data = I2C1->DR;
return data;
}
void mma_stop(void) {
// send stop condition
I2C1->CR1 |= I2C_CR1_STOP;
}