【Silicon Labs EFR32xG24 开发套件】利用IIC读温湿度并用串口打印

meiyao

【Silicon Labs EFR32xG24 开发套件】板小，但是兼容了好几款传感器，麻雀虽小五脏俱全。
我继续探索板卡自带的温湿度传感器S。从原理图中可以看到传感器的型号是：Si7021。采用了Silicon Labs的第二代RH感测解决方案，温度测量范围从-40~+125℃，精度高达±0.4℃；相对湿度可以从0~80%RH进行准确测量。
下图为温湿度传感器参数：

再来一个附件：

Si7021.pdf (1.57 MB, 下载次数: 0)

传感器我就不多介绍，详细的参数请看规格书，下面我们看一下原理图：

SI7021是用IIC通信的，IIC上面挂了好几个传感器。

通过TS3A4751连接在PC04 PC05 IO口上。
下图简单的说明，和Si7021如何连接到EFR32MG24。

下在看代码：
IIC的初始化：
  I2C_TransferReturn_TypeDef ret;
  uint8_t cmdReadId2[2] = SI7021_CMD_READ_ID_BYTE2;
  uint8_t deviceId[8];
  // Wait for sensor to become ready
  sl_sleeptimer_delay_millisecond(80);
  // Check for device presence  and compare device ID
  ret = SI7021_transaction(I2C_FLAG_WRITE_READ, cmdReadId2, 2, deviceId, 8);
  // Make sure transfer was successful
  EFM_ASSERT(ret == i2cTransferDone);
  // Check the Received Device ID
  EFM_ASSERT(deviceId[0] == SI7021_DEVICE_ID);
  // Initialize LED PWM module
  initialise_temp_limits();
  // Initialize Periodic timer
  initialise_timer();
  // stdout is redirected to VCOM in project configuration
  printf("Welcome to the I2CSPM example application\r\n");

读取传感器的值：
  sl_atomic_load(local_read_sensor_data, read_sensor_data);

  if (local_read_sensor_data) {
// Measure the current humidity and temperature
SI7021_measure(&relative_humidity, &temperature);
// Print the current humidity and temperature to vcom
printf("\r\n");
printf("Relative Humidity = %ld%%\r\n", relative_humidity);
printf("Temperature = %ld C\r\n", temperature);
// Set appropriate LEDs (led0 or 1) based on temperature
set_leds(temperature);
// Reset the flag
local_read_sensor_data = false;
sl_atomic_store(read_sensor_data, local_read_sensor_data);

通过串口打印出传感器的值：一个是温度，一个是温度。

视频：
https://www.bilibili.com/video/BV1CV4y1A7yV/?vd_source=0e4686609dd9c60a63b3f7fe54080c03

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