149 lines
3.2 KiB
C
149 lines
3.2 KiB
C
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#include "iic.h"
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/* Software I2C delay (microseconds), based on SysTick */
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static void delayUs(uint16_t us)
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{
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uint32_t start = SysTick->VAL;
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uint32_t ticks = us * (SystemCoreClock / 1000000);
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if (start < ticks) {
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while (SysTick->VAL > start);
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while (SysTick->VAL < (SysTick->LOAD - (ticks - start)));
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} else {
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while ((SysTick->VAL < start) && (SysTick->VAL >= (start - ticks)));
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}
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}
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/* I2C Interface Initialization */
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void iicInit(void)
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{
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GPIO_InitTypeDef GPIO_InitStruct;
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__HAL_RCC_GPIOA_CLK_ENABLE();
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/* SDA - PA12, open-drain output */
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GPIO_InitStruct.Pin = SDA_Pin;
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GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_OD;
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GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;
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HAL_GPIO_Init(SDA_GPIO_Port, &GPIO_InitStruct);
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/* SCL - PA11, push-pull output */
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GPIO_InitStruct.Pin = SCL_Pin;
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GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
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GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;
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HAL_GPIO_Init(SCL_GPIO_Port, &GPIO_InitStruct);
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IIC_SCL_H;
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IIC_SDA_H;
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/* 总线恢复：若上次运行在 I2C 传输中途被复位（烧录/看门狗/OTA 复位），
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* EEPROM 可能一直拉着 SDA 不放，导致后续通信卡死。
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* 检测 SDA 被拉低时，补 9 个 SCL 时钟把从机的当前字节推完，再发 STOP 释放总线 */
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if (READ_SDA == 0) {
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for (int i = 0; i < 9; i++) {
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IIC_SCL_L;
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delayUs(5);
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IIC_SCL_H;
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delayUs(5);
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}
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iicStop();
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}
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}
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/* I2C Start Signal */
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void iicStart(void)
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{
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IIC_SDA_H;
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IIC_SCL_H;
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delayUs(4);
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IIC_SDA_L; /* SCL high, SDA high->low = start */
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}
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/* I2C Stop Signal */
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void iicStop(void)
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{
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IIC_SDA_L;
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IIC_SCL_H;
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delayUs(4);
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IIC_SDA_H; /* SCL high, SDA low->high = stop */
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}
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/* Wait for ACK: returns 0=OK, 1=timeout */
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uint8_t iicWaitAck(void)
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{
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unsigned char timeout = 0;
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IIC_SDA_H;
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IIC_SCL_H;
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while (READ_SDA) {
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timeout++;
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if (timeout > 250) {
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iicStop();
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return 1;
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}
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delayUs(2);
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}
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IIC_SCL_L;
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delayUs(20);
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return 0;
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}
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/* Send One Byte (MSB first), return ACK status: 0=ACK, 1=NACK/timeout */
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uint8_t iicSendByteAck(uint8_t txd)
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{
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unsigned char t;
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IIC_SCL_L;
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for (t = 0; t < 8; t++) {
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IIC_SDA_OUT(((txd & 0x80) >> 7));
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txd <<= 1;
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delayUs(2);
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IIC_SCL_H;
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delayUs(2);
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IIC_SCL_L;
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}
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return iicWaitAck();
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}
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/* Send One Byte (MSB first), legacy API without ACK return */
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void iicSendByte(uint8_t txd)
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{
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(void)iicSendByteAck(txd);
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}
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/* Read One Byte; ack=1 send ACK, ack=0 send NACK */
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unsigned char iicReadByte(uint8_t ack)
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{
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unsigned char i;
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unsigned char receive = 0;
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IIC_SCL_L;
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delayUs(20);
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for (i = 0; i < 8; i++) {
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IIC_SCL_H;
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delayUs(20);
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receive <<= 1;
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if (READ_SDA) receive++;
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delayUs(20);
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IIC_SCL_L;
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delayUs(20);
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}
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if (!ack) {
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/* NACK */
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IIC_SDA_H;
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IIC_SCL_H;
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delayUs(2);
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IIC_SCL_L;
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} else {
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/* ACK */
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IIC_SDA_L;
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IIC_SCL_H;
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delayUs(2);
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IIC_SCL_L;
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IIC_SDA_H;
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}
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return receive;
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}
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