今天主要和大家谈谈如何使用鸿蒙系统提取AHT使用20个温湿度传感器的值ADC位数为20Bit，它具有体积小、精度高、成本低的优点。
I2C支持标准1000Hz，高速400KHz
根据以上分析，温湿度传感器的基本实现原理和方法可以集中在代码的具体实现上。
#include "aht20.h"#include <stdio.h>#include <string.h>#include <unistd.h>#include "wifiiot_i2c.h"#include "wifiiot_errno.h"#define AHT20_I2C_IDX WIFI_IOT_I2C_IDX_0#define AHT20_STARTUP_TIME 20*1000 // 上电启动时间#define AHT20_CALIBRATION_TIME 40*1000 // 初始化(校准)时间#define AHT20_MEASURE_TIME 75*1000 // 测量时间#define AHT20_DEVICE_ADDR 0x38#define AHT20_READ_ADDR ((0x38<<1)|0x1)#define AHT20_WRITE_ADDR ((0x38<<1)|0x0)#define AHT20_CMD_CALIBRATION 0xBE // 初始化(校准)命令#define AHT20_CMD_CALIBRATION_ARG0 0x08#define AHT20_CMD_CALIBRATION_ARG1 0x00/*** 主机发出测量指令(0xAC）延迟超过75毫秒后，读取转换后的数据，判断返回状态是否正常。* 若状态比特[Bit7]0代表数据可以正常读取，1时传感器处于忙碌状态，主机需要等待数据处理。**/#define AHT20_CMD_TRIGGER 0xAC // 触发测量命令#define AHT20_CMD_TRIGGER_ARG0 0x33#define AHT20_CMD_TRIGGER_ARG1 0x00// 用于在无需关闭和再次打开电源的情况下，重新启动传感器系统，软复位所需时间不超过20 毫秒#define AHT20_CMD_RESET 0xBA // 软复位命令#define AHT20_CMD_STATUS 0x71 // 获取状态命令/*** STATUS 命令回复：* 1. 初始化后触发测量前，STATUS 只回复 1B 状态值；* 2. 触发测量后，STATUS 回复6B：1B 状态值 2B 湿度 4b湿度 4b温度 2B 温度* RH = Srh / 2^20 * 100%* T = St / 2^20 * 200 - 50**/#define AHT20_STATUS_BUSY_SHIFT 7 // bit[7] Busy indication#define AHT20_STATUS_BUSY_MASK (0x1<<AHT20_STATUS_BUSY_SHIFT)#define AHT20_STATUS_BUSY(status) ((status & AHT20_STATUS_BUSY_MASK) >> AHT20_STATUS_BUSY_SHIFT)#define AHT20_STATUS_MODE_SHIFT 5 // bit[6:5] Mode Status#define AHT20_STATUS_MODE_MASK (0x3<<AHT20_STATUS_MODE_SHIFT)#define AHT20_STATUS_MODE(status) ((status & AHT20_STATUS_MODE_MASK) >> AHT20_STATUS_MODE_SHIFT)// bit[4] Reserved#define AHT20_STATUS_CALI_SHIFT 3 // bit[3] CAL Enable#define AHT20_STATUS_CALI_MASK (0x1<<AHT20_STATUS_CALI_SHIFT)#define AHT20_STATUS_CALI(status) ((status & AHT20_STATUS_CALI_MASK) >> AHT20_STATUS_CALI_SHIFT)// bit[2:0] Reserved#define AHT20_STATUS_RESPONSE_MAX 6#define AHT20_RESOLUTION (1<<20) // 2^20#define AHT20_MAX_RETRY 10static uint32_t AHT20_Read(uint8_t* buffer, uint32_t buffLen){WifiIotI2cData data = { 0 };data.receiveBuf = buffer;data.receiveLen = buffLen;uint32_t retval = I2cRead(AHT20_I2C_IDX, AHT20_READ_ADDR, &data);if (retval != WIFI_IOT_SUCCESS) {printf("I2cRead() failed, %0X!\n", retval);return retval;}return WIFI_IOT_SUCCESS;}static uint32_t AHT20_Write(uint8_t* buffer, uint32_t buffLen){WifiIotI2cData data = { 0 };data.sendBuf = buffer;data.sendLen = buffLen;uint32_t retval = I2cWrite(AHT20_I2C_IDX, AHT20_WRITE_ADDR, &data);if (retval != WIFI_IOT_SUCCESS) {printf("I2cWrite(X) failed, %0X!\n", buffer[0], retval);return retval;}return WIFI_IOT_SUCCESS;}// 发送获取状态命令static uint32_t AHT20_StatusCommand(void){uint8_t statusCmd[] = { AHT20_CMD_STATUS };return AHT20_Write(statusCmd, sizeof(statusCmd)); }// 发送软复位命令static uint32_t AHT20_ResetCommand(void){uint8_t resetCmd[] = {AHT20_CMD_RESET};return AHT20_Write(resetCmd, sizeof(resetCmd));}// 发送初始化校准命令static uint32_t AHT20_CalibrateCommand(void){uint8_t clibrateCmd[] = {AHT20_CMD_CALIBRATION, AHT20_CMD_CALIBRATION_ARG0, AHT20_CMD_CALIBRATION_ARG1};return AHT20_Write(clibrateCmd, sizeof(clibrateCmd));}// 读取温湿度值之前， 首先要看状态字的校准使能位Bit[3]是否为 1(通过发送0x71可以获取一个字节的状态字)，// 如果不为1，要发送0xBE命令(初始化)，此命令参数有两个字节， 第一个字节为0x08，第二个字节为0x00。uint32_t AHT20_Calibrate(void){uint32_t retval = 0;uint8_t buffer[AHT20_STATUS_RESPONSE_MAX];memset(&buffer, 0x0, sizeof(buffer));retval = AHT20_StatusCommand();if (retval != WIFI_IOT_SUCCESS) {return retval;}retval = AHT20_Read(buffer, sizeof(buffer));if (retval != WIFI_IOT_SUCCESS) {return retval;}if (AHT20_STATUS_BUSY(buffer[0]) || !AHT20_STATUS_CALI(buffer[0])) {retval = AHT20_ResetCommand();if (retval != WIFI_IOT_SUCCESS) {return retval;}usleep(AHT20_STARTUP_TIME);retval = AHT20_CalibrateCommand();usleep(AHT20_CALIBRATION_TIME);return retval;}return WIFI_IOT_SUCCESS;}// 发送 触发测量 命令，开始测量uint32_t AHT20_StartMeasure(void){uint8_t triggerCmd[] = {AHT20_CMD_TRIGGER, AHT20_CMD_TRIGGER_ARG0, AHT20_CMD_TRIGGER_ARG1};return AHT20_Write(triggerCmd, sizeof(triggerCmd));}// 接收测量结果，拼接转换为标准值uint32_t AHT20_GetMeasureResult(float* temp, float* humi){uint32_t retval = 0, i = 0;if (temp == NULL || humi == NULL) {return WIFI_IOT_FAILURE;}uint8_t buffer[AHT20_STATUS_RESPONSE_MAX];memset(&buffer, 0x0, sizeof(buffer));retval = AHT20_Read(buffer, sizeof(buffer)); // recv status command resultif (retval != WIFI_IOT_SUCCESS) {return retval;}for (i = 0; AHT20_STATUS_BUSY(buffer[0]) && i < AHT20_MAX_RETRY; i++) {// printf("AHT20 device busy, retry %d/%d!\r\n", i, AHT20_MAX_RETRY);usleep(AHT20_MEASURE_TIME);retval = AHT20_Read(buffer, sizeof(buffer)); // recv status command resultif (retval != WIFI_IOT_SUCCESS) {return retval;}}if (i >= AHT20_MAX_RETRY) {printf("AHT20 device always busy!\r\n");return WIFI_IOT_FAILURE;}uint32_t humiRaw = buffer[1];humiRaw = (humiRaw << 8) | buffer[2];humiRaw = (humiRaw << 4) | ((buffer[3] & 0xF0) >> 4);*humi = humiRaw / (float)AHT20_RESOLUTION * 100;uint32_t tempRaw = buffer[3] & 0x0F;tempRaw = (tempRaw << 8) | buffer[4];tempRaw = (tempRaw << 8) | buffer[5];*temp = tempRaw / (float)AHT20_RESOLUTION * 200 - 50;// printf("humi = %05X, %f, temp= %05X, %f\r\n", humiRaw, *humi, tempRaw, *temp);return WIFI_IOT_SUCCESS;}
#include "aht20.h"#include <stdio.h>#include <unistd.h>#include "ohos_init.h"#include "cmsis_os2.h"#include "wifiiot_gpio.h"#include "wifiiot_gpio_ex.h"#include "wifiiot_i2c.h"void Aht20TestTask(void* arg){(void) arg;uint32_t retval = 0;IoSetFunc(WIFI_IOT_IO_NAME_GPIO_13, WIFI_IOT_IO_FUNC_GPIO_13_I2C0_SDA);IoSetFunc(WIFI_IOT_IO_NAME_GPIO_14, WIFI_IOT_IO_FUNC_GPIO_14_I2C0_SCL);I2cInit(WIFI_IOT_I2C_IDX_0, 400*1000);retval = AHT20_Calibrate();printf("AHT20_Calibrate: %d\r\n", retval);while (1) {float temp = 0.0, humi = 0.0;retval = AHT20_StartMeasure();printf("AHT20_StartMeasure: %d\r\n", retval);retval = AHT20_GetMeasureResult(&temp, &humi);printf("AHT20_GetMeasureResult: %d, temp = %.2f, humi = %.2f\r\n", retval, temp, humi);sleep(1);}}void Aht20Test(void){osThreadAttr_t attr;attr.name = "Aht20Task";attr.attr_bits = 0U;attr.cb_mem = NULL;attr.cb_size = 0U;attr.stack_mem = NULL;attr.stack_size = 4096;attr.priority = osPriorityNormal;if (osThreadNew(Aht20TestTask, NULL, &attr) == NULL) {printf("[Aht20Test] Failed to create Aht20TestTask!\n");}}APP_FEATURE_INIT(Aht20Test);
具体的操作实现如下视频所示。