first commit

inc/aht20.h

@@ -0,0 +1,40 @@
+#ifndef AHT20_H
+#define AHT20_H
+
+#include <stdint.h>
+
+#define AHT20_ADDR 0x38           // AHT default i2c address
+#define AHT20_CMD_CALIBRATE 0xBE  // Calibration command
+#define AHT20_CMD_TRIGGER 0xAC    // Trigger reading command
+#define AHT20_CMD_SOFTRESET 0xBA  // Soft reset command
+#define AHT20_CMD_STATUS 0x71
+#define AHT20_STATUS_BUSY 0x80        // Status bit for busy
+#define AHT20_STATUS_CALIBRATED 0x08  // Status bit for calibrated
+
+#define AHT20_OK 0x00
+#define AHT20_ERR_INIT 0x01  // Initialization or Calibration failed
+#define AHT20_ERR_BUSY 0x02  // Sensor measurement timeout
+#define AHT20_ERR_CRC 0x03   // Data corruption detected
+#define AHT20_ERR_I2C 0x04   // Generic I2C Bus error (NACK)
+
+#define STATUS_BUSY_BIT (1 << 7)
+#define STATUS_CAL_BIT (1 << 3)
+
+typedef struct {
+  uint32_t hum_p_x100;  // %RH * 100
+  int32_t temp_c_x100;  // DegC * 100
+} aht20_data;
+
+/**
+ * Init sensor
+ * Checks status 0x71 and performs calibration (0xBE) if required
+ */
+uint8_t aht20_init(void);
+
+/**
+ * Trigger measurement, wait >80ms, poll busy bit, and read data
+ * Checks CRC8
+ */
+uint8_t aht20_read(aht20_data* out_data);
+
+#endif  // AHT20_H