I2C
簡介
I2C總線是由Philips公司開發的一種簡單、雙向二線制同步串行總線。SDA（串行數據線）和SCL（串行時鐘線）都是雙向I/O線，接口電路爲開漏輸出．需通過上拉電阻接電源VCC.
I2C（內部集成電路）總線接口處理微控制器與串行 I2C 總線間的通信。它提供多主模式功
能，可以控制所有 I2C 總線特定的序列、協議、仲裁和時序。它支持標準模式 (Sm)、快速模
式 (Fm) 和超快速模式 (Fm+)。
- 從模式和主模式
- 多主模式功能
- 標準速度模式（高達 100 kHz）
- 快速模式（高達 400 kHz）
- 超快速模式（高達 1 MHz）
- 7 位和 10 位尋址模式
I2C start/stop
- 開始信號：SCL爲高電平時，SDA由高電平向低電平跳變，開始傳送數據。
- 結束信號：SCL爲高電平時，SDA由低電平向高電平跳變，結束傳送數據。
I2C read
- Master發送I2C addr（7bit）和w操作0（1bit），等待ACK
- Slave發送ACK
- Master發送reg addr（8bit），等待ACK
- Slave發送ACK
- Master發起START
- Master發送I2C addr（7bit）和r操作1（1bit），等待ACK
- Slave發送ACK
- Slave發送data（8bit），即寄存器裏的值
- Master發送ACK。或者Master發送NACK，要求結束。
- 第8步和第9步可以重複多次，即順序讀多個寄存器
I2C write
- Master發起START
- Master發送I2C addr（7bit）和w操作0（1bit），等待ACK
- Slave發送ACK
- Master發送reg addr（8bit），等待ACK
- Slave發送ACK
- Master發送data（8bit），即要寫入寄存器中的數據，等待ACK
- Slave發送ACK
- 第6步和第7步可以重複多次，即順序寫多個寄存器
- Master發起STOP
例子
I2C signal diagram: SDA(green) and SCL(yellow)
write 0x55 DAC
USB to I2C
通過USB虛擬串口實現PC與I2C設備進行通信。使用STM32L073xx MCU，硬件I2C和軟件模擬I2C，用看門狗檢測運行狀態。
底層firmware實現代碼和硬件電路圖見鏈接：
- 此時I2C是做主機–>https://github.com/tclxspy/USB_I2C_73
- 另附上I2C做從機的代碼–>https://github.com/tclxspy/QSFP28_PSM4
USB安裝成功：
串口助手調試
部分代碼main.c
#include "main.h"
#include "stm32l0xx_hal.h"
#include "usb_device.h"
#include "i2c.h"
#include "soft_i2c.h"
#include "stm32l0xx_nucleo.h"
#include "usbd_cdc_if.h"
#include "modsel.h"
/* Buffer used for transmission */
//uint8_t aTxBuffer[] = {0x33, 0x34};
//uint8_t aTxBuffer[] = {0x46, 0x54};//{"FT"}
uint8_t aTxBuffer[RXBUFFERSIZE];
/* Buffer used for reception */
uint8_t aRxBuffer[RXBUFFERSIZE];
__IO uint16_t hTxNumData = 0;
__IO uint16_t hRxNumData = 0;
uint8_t bTransferRequest = 0;
/* USER CODE BEGIN Includes */
/* USER CODE END Includes */
/* Private variables ---------------------------------------------------------*/
I2C_HandleTypeDef I2cHandle;
IWDG_HandleTypeDef hiwdg;
/* USER CODE BEGIN PV */
/* Private variables ---------------------------------------------------------*/
/* USER CODE END PV */
/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_IWDG_Init(void);
/* USER CODE BEGIN PFP */
/* Private function prototypes -----------------------------------------------*/
/* USER CODE END PFP */
/* USER CODE BEGIN 0 */
/* USER CODE END 0 */
int main(void)
{
/* USER CODE BEGIN 1 */
/* USER CODE END 1 */
/* MCU Configuration----------------------------------------------------------*/
/* Reset of all peripherals, Initializes the Flash interface and the Systick. */
HAL_Init();
/* USER CODE BEGIN Init */
/* USER CODE END Init */
/* Configure the system clock */
SystemClock_Config();
/* USER CODE BEGIN SysInit */
/* USER CODE END SysInit */
/* Initialize all configured peripherals */
MX_GPIO_Init();
MODSELL_Init();
/* I2C2 init function */
#ifdef HARDWARE_I2C
I2C_Init();
#else
Soft_I2C_Init();
#endif /* HARDWARE_I2C */
MX_IWDG_Init();
MX_USB_DEVICE_Init();
uint8_t len;
uint8_t t;
uint8_t deviceAddress;
uint8_t regAddress;
uint8_t length;
uint8_t read_write;
#ifdef HARDWARE_I2C
while(1)
{
if(USB_USART_RX_STA&0x8000)
{
read_write = USB_USART_RX_Buffer[3];
deviceAddress = USB_USART_RX_Buffer[4];
regAddress = USB_USART_RX_Buffer[5];
length = USB_USART_RX_Buffer[6];
len = USB_USART_RX_STA&0x3FFF;
USB_USART_RX_STA=0;
for(t=0;t<len-8;t++)
{
aTxBuffer[t]=USB_USART_RX_Buffer[t+8];
}
if(read_write==MASTER_REQ_READ)
{
do
{
if(HAL_I2C_Mem_Read_IT(&I2cHandle, (uint16_t)deviceAddress, regAddress, I2C_MEMADD_SIZE_8BIT, (uint8_t*)aRxBuffer, length)!= HAL_OK)
{
/* Error_Handler() function is called when error occurs. */
Error_Handler();
}
while (HAL_I2C_GetState(&I2cHandle) != HAL_I2C_STATE_READY){}
}
while(HAL_I2C_GetError(&I2cHandle) == HAL_I2C_ERROR_AF);
CDC_Transmit_FS(aRxBuffer, length);
}
if(read_write==MASTER_REQ_WRITE)
{
do
{
if(HAL_I2C_Mem_Write_IT(&I2cHandle, (uint16_t)deviceAddress, regAddress, I2C_MEMADD_SIZE_8BIT, (uint8_t*)&aTxBuffer, len-8)!= HAL_OK)
{
/* Error_Handler() function is called when error occurs. */
Error_Handler();
}
while (HAL_I2C_GetState(&I2cHandle) != HAL_I2C_STATE_READY){}
}
while(HAL_I2C_GetError(&I2cHandle) == HAL_I2C_ERROR_AF);
}
}
/* Refresh IWDG: reload counter */
if(HAL_IWDG_Refresh(&hiwdg) != HAL_OK)
{
/* Refresh Error */
Error_Handler();
}
}
#else
while(1)
{
if(USB_USART_RX_STA&0x8000)
{
read_write = USB_USART_RX_Buffer[3];
deviceAddress = USB_USART_RX_Buffer[4];
regAddress = USB_USART_RX_Buffer[5];
length = USB_USART_RX_Buffer[6];
len = USB_USART_RX_STA&0x3FFF;
USB_USART_RX_STA=0;
for(t=0;t<len-8;t++)
{
aTxBuffer[t]=USB_USART_RX_Buffer[t+8];
}
if(read_write==MASTER_REQ_READ)
{
Soft_I2C_Read_Reg(deviceAddress, regAddress, aRxBuffer, length);
CDC_Transmit_FS(aRxBuffer, length);
}
if(read_write==MASTER_REQ_WRITE)
{
Soft_I2C_Send_Reg(deviceAddress, regAddress, aTxBuffer, len-8);
}
}
/* Refresh IWDG: reload counter */
if(HAL_IWDG_Refresh(&hiwdg) != HAL_OK)
{
/* Refresh Error */
Error_Handler();
}
}
#endif /* HARDWARE_I2C */
}
/** System Clock Configuration
*/
void SystemClock_Config(void)
{
RCC_OscInitTypeDef RCC_OscInitStruct;
RCC_ClkInitTypeDef RCC_ClkInitStruct;
RCC_PeriphCLKInitTypeDef PeriphClkInit;
/**Configure the main internal regulator output voltage
*/
__HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);
/**Initializes the CPU, AHB and APB busses clocks
*/
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI|RCC_OSCILLATORTYPE_HSI48;
RCC_OscInitStruct.HSIState = RCC_HSI_ON;
RCC_OscInitStruct.HSICalibrationValue = 16;
RCC_OscInitStruct.HSI48State = RCC_HSI48_ON;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSI;
RCC_OscInitStruct.PLL.PLLMUL = RCC_PLLMUL_4;
RCC_OscInitStruct.PLL.PLLDIV = RCC_PLLDIV_2;
if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
{
_Error_Handler(__FILE__, __LINE__);
}
/**Initializes the CPU, AHB and APB busses clocks
*/
RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
|RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_1) != HAL_OK)
{
_Error_Handler(__FILE__, __LINE__);
}
PeriphClkInit.PeriphClockSelection = RCC_PERIPHCLK_USB;
PeriphClkInit.UsbClockSelection = RCC_USBCLKSOURCE_HSI48;
if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInit) != HAL_OK)
{
_Error_Handler(__FILE__, __LINE__);
}
/**Configure the Systick interrupt time
*/
HAL_SYSTICK_Config(HAL_RCC_GetHCLKFreq()/1000);
/**Configure the Systick
*/
HAL_SYSTICK_CLKSourceConfig(SYSTICK_CLKSOURCE_HCLK);
/* SysTick_IRQn interrupt configuration */
HAL_NVIC_SetPriority(SysTick_IRQn, 0, 0);
}
/** Pinout Configuration
*/
static void MX_GPIO_Init(void)
{
/* GPIO Ports Clock Enable */
//__HAL_RCC_GPIOB_CLK_ENABLE();
__HAL_RCC_GPIOA_CLK_ENABLE();
}
static void MX_IWDG_Init(void)
{
hiwdg.Instance = IWDG;
hiwdg.Init.Prescaler = IWDG_PRESCALER_64;
hiwdg.Init.Window = 0xfff;
hiwdg.Init.Reload = 0xfff;
if (HAL_IWDG_Init(&hiwdg) != HAL_OK)
{
_Error_Handler(__FILE__, __LINE__);
}
}
/**
* @brief This function is executed in case of error occurrence.
* @param None
* @retval None
*/
void _Error_Handler(char * file, int line)
{
/* USER CODE BEGIN Error_Handler_Debug */
/* User can add his own implementation to report the HAL error return state */
while(1)
{
}
/* USER CODE END Error_Handler_Debug */
}
#ifdef USE_FULL_ASSERT
/**
* @brief Reports the name of the source file and the source line number
* where the assert_param error has occurred.
* @param file: pointer to the source file name
* @param line: assert_param error line source number
* @retval None
*/
void assert_failed(uint8_t* file, uint32_t line)
{
/* USER CODE BEGIN 6 */
/* User can add his own implementation to report the file name and line number,
ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */
/* USER CODE END 6 */
}
#endif