今天主要和大家聊一聊，如何使用鸿蒙系统去提取AHT20的温湿度传感器的数值，该传感器采用ADC位数为20Bit，具有体积小，精度高和成本低的优点。
第一：温湿度传感器基本参数
管脚定义与参考电路
I2C时序特性----支持标准100Hz，高速400KHz
第二：温度代码具体实现
上面分析了，温湿度传感器的基本实现原理与方法，主要精力可以放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 /** * 传感器在采集时需要时间,主机发出测量指令（0xAC）后，延时75毫秒以上再读取转换后的数据并判断返回的状态位是否正常。 * 若状态比特位[Bit7]为0代表数据可正常读取，为1时传感器为忙状态，主机需要等待数据处理完成。 **/ #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. 初始化后触发测量之前，STATUS 只回复 1B 状态值； * 2. 触发测量之后，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 10 static 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(%02X) 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 result if (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 result if (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; }
接下来，可以利用鸿蒙系统对温湿度传感器里面的温度数据进行读取，然后再将获取到的温湿度数据进行显示输出
#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);
