【学习打卡】-----利用鸿蒙系统实现对温湿度传感器数据操作

​ 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。

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第一：温湿度传感器基本参数

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管脚定义与参考电路

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I2C时序特性----支持标准100Hz，高速400KHz

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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);

具体的操作实现如视频所示。

第三：视频显示效果

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