kopia lustrzana https://github.com/micropython/micropython
129 wiersze
3.9 KiB
C
129 wiersze
3.9 KiB
C
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#include <stdio.h>
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#include <stm32f4xx.h>
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#include <stm32f4xx_rcc.h>
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#include <stm32f4xx_gpio.h>
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#include "mma.h"
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void mma_init() {
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RCC->APB1ENR |= RCC_APB1ENR_I2C1EN; // enable I2C1
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//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 */);
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//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 */);
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//gpio_pin_af(GPIOB, 6, 4 /* AF 4 for I2C1 */);
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//gpio_pin_af(GPIOB, 7, 4 /* AF 4 for I2C1 */);
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// XXX untested GPIO init! (was above code)
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GPIO_InitTypeDef GPIO_InitStructure;
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GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6 | GPIO_Pin_7;
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GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
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GPIO_InitStructure.GPIO_OType = GPIO_OType_OD;
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GPIO_InitStructure.GPIO_Speed = GPIO_Speed_25MHz;
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GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL ;
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GPIO_Init(GPIOB, &GPIO_InitStructure);
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GPIO_PinAFConfig(GPIOB, GPIO_PinSource6, GPIO_AF_I2C1);
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GPIO_PinAFConfig(GPIOB, GPIO_PinSource7, GPIO_AF_I2C1);
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// get clock speeds
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RCC_ClocksTypeDef rcc_clocks;
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RCC_GetClocksFreq(&rcc_clocks);
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// disable the I2C peripheral before we configure it
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I2C1->CR1 &= ~I2C_CR1_PE;
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// program peripheral input clock
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I2C1->CR2 = 4; // no interrupts; 4 MHz (hopefully!) (could go up to 42MHz)
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// configure clock control reg
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uint32_t freq = rcc_clocks.PCLK1_Frequency / (100000 << 1); // want 100kHz, this is the formula for freq
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I2C1->CCR = freq; // standard mode (speed), freq calculated as above
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// configure rise time reg
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I2C1->TRISE = (rcc_clocks.PCLK1_Frequency / 1000000) + 1; // formula for trise, gives maximum rise time
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// enable the I2C peripheral
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I2C1->CR1 |= I2C_CR1_PE;
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// set START bit in CR1 to generate a start cond!
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}
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static uint32_t i2c_get_sr() {
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// must read SR1 first, then SR2, as the read can clear some flags
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uint32_t sr1 = I2C1->SR1;
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uint32_t sr2 = I2C1->SR2;
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return (sr2 << 16) | sr1;
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}
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void mma_restart(uint8_t addr, int write) {
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// send start condition
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I2C1->CR1 |= I2C_CR1_START;
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// wait for BUSY, MSL and SB --> Slave has acknowledged start condition
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while ((i2c_get_sr() & 0x00030001) != 0x00030001) {
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}
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if (write) {
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// send address and write bit
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I2C1->DR = (addr << 1) | 0;
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// wait for BUSY, MSL, ADDR, TXE and TRA
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while ((i2c_get_sr() & 0x00070082) != 0x00070082) {
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}
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} else {
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// send address and read bit
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I2C1->DR = (addr << 1) | 1;
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// wait for BUSY, MSL and ADDR flags
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while ((i2c_get_sr() & 0x00030002) != 0x00030002) {
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}
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}
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}
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void mma_start(uint8_t addr, int write) {
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// wait until I2C is not busy
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while (I2C1->SR2 & I2C_SR2_BUSY) {
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}
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// do rest of start
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mma_restart(addr, write);
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}
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void mma_send_byte(uint8_t data) {
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// send byte
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I2C1->DR = data;
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// wait for TRA, BUSY, MSL, TXE and BTF (byte transmitted)
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int timeout = 1000000;
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while ((i2c_get_sr() & 0x00070084) != 0x00070084) {
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if (timeout-- <= 0) {
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printf("mma_send_byte timed out!\n");
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break;
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}
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}
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}
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uint8_t mma_read_ack() {
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// enable ACK of received byte
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I2C1->CR1 |= I2C_CR1_ACK;
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// wait for BUSY, MSL and RXNE (byte received)
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while ((i2c_get_sr() & 0x00030040) != 0x00030040) {
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}
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// read and return data
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uint8_t data = I2C1->DR;
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return data;
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}
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uint8_t mma_read_nack() {
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// disable ACK of received byte (to indicate end of receiving)
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I2C1->CR1 &= (uint16_t)~((uint16_t)I2C_CR1_ACK);
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// last byte should apparently also generate a stop condition
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I2C1->CR1 |= I2C_CR1_STOP;
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// wait for BUSY, MSL and RXNE (byte received)
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while ((i2c_get_sr() & 0x00030040) != 0x00030040) {
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}
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// read and return data
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uint8_t data = I2C1->DR;
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return data;
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}
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void mma_stop() {
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// send stop condition
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I2C1->CR1 |= I2C_CR1_STOP;
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}
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