get bem280 humidity reading working

bme280.c

@@ -46,37 +46,7 @@
 
 // #define REG_PRESSURE_XLSB _u(0xF9)
 // #define REG_PRESSURE_LSB _u(0xF8)
-#define REG_PRESSURE_MSB _u(0xF7)
+// #define REG_PRESSURE_MSB _u(0xF7)
-
-// calibration registers
-#define REG_DIG_T1_LSB _u(0x88)
-// #define REG_DIG_T1_MSB _u(0x89)
-// #define REG_DIG_T2_LSB _u(0x8A)
-// #define REG_DIG_T2_MSB _u(0x8B)
-// #define REG_DIG_T3_LSB _u(0x8C)
-// #define REG_DIG_T3_MSB _u(0x8D)
-// #define REG_DIG_P1_LSB _u(0x8E)
-// #define REG_DIG_P1_MSB _u(0x8F)
-// #define REG_DIG_P2_LSB _u(0x90)
-// #define REG_DIG_P2_MSB _u(0x91)
-// #define REG_DIG_P3_LSB _u(0x92)
-// #define REG_DIG_P3_MSB _u(0x93)
-// #define REG_DIG_P4_LSB _u(0x94)
-// #define REG_DIG_P4_MSB _u(0x95)
-// #define REG_DIG_P5_LSB _u(0x96)
-// #define REG_DIG_P5_MSB _u(0x97)
-// #define REG_DIG_P6_LSB _u(0x98)
-// #define REG_DIG_P6_MSB _u(0x99)
-// #define REG_DIG_P7_LSB _u(0x9A)
-// #define REG_DIG_P7_MSB _u(0x9B)
-// #define REG_DIG_P8_LSB _u(0x9C)
-// #define REG_DIG_P8_MSB _u(0x9D)
-// #define REG_DIG_P9_LSB _u(0x9E)
-// #define REG_DIG_P9_MSB _u(0x9F)
-
-// number of calibration registers to be read
-// 17 * 2  = 34
-#define NUM_COMPENSATION_PARAMS 34
 
 static void bmp280_get_compensation_params(i2c_inst_t *i2c,
                                            bme280_compensation_params *params) {
@@ -85,15 +55,12 @@ static void bmp280_get_compensation_params(i2c_inst_t *i2c,
   // there are 3 temperature params, and 9 pressure params, each with a LSB
   // and MSB register, so we read from 24 registers
 
-  uint8_t buf[NUM_COMPENSATION_PARAMS] = {0};
+  // read the first 24 compensation params
-  uint8_t reg = REG_DIG_T1_LSB;
+  uint8_t buf[25] = {0};
-  i2c_write_blocking(i2c, ADDR, &reg, 1,
+  uint8_t reg = 0x88;
-                     true); // true to keep master control of bus
+  i2c_write_blocking(i2c, ADDR, &reg, 1, true); // true to keep master control of bus
-  // read in one go as register addresses auto-increment
+  i2c_read_blocking(i2c, ADDR, buf, 25, false);
-  i2c_read_blocking(i2c, ADDR, buf, NUM_COMPENSATION_PARAMS,
-                    false); // false, we're done reading
 
-  // store these in a struct for later use
   params->dig_t1 = (uint16_t)(buf[1] << 8) | buf[0];
   params->dig_t2 = (int16_t)(buf[3] << 8) | buf[2];
   params->dig_t3 = (int16_t)(buf[5] << 8) | buf[4];
@@ -107,12 +74,21 @@ static void bmp280_get_compensation_params(i2c_inst_t *i2c,
   params->dig_p7 = (int16_t)(buf[19] << 8) | buf[18];
   params->dig_p8 = (int16_t)(buf[21] << 8) | buf[20];
   params->dig_p9 = (int16_t)(buf[23] << 8) | buf[22];
+  params->dig_h1 = (int16_t)buf[24];
 
-  params->dig_h1 = (int16_t)(buf[25] << 8) | buf[24];
+  // read second set of compensation params
-  params->dig_h2 = (int16_t)(buf[27] << 8) | buf[26];
+  reg = 0xE1;
-  params->dig_h3 = (int16_t)(buf[29] << 8) | buf[28];
+  i2c_write_blocking(i2c, ADDR, &reg, 1, true); // true to keep master control of bus
-  params->dig_h4 = (int16_t)(buf[31] << 8) | buf[30];
+  i2c_read_blocking(i2c, ADDR, buf, 7, false); // false, we're done reading
-  params->dig_h5 = (int16_t)(buf[33] << 8) | buf[32];
+  params->dig_h2 = (int16_t)(int16_t)(buf[1] << 8) | buf[0];
+  params->dig_h3 = buf[2];
+  int16_t dig_h4_msb = (int16_t)(int8_t)buf[3] * 16;
+  int16_t dig_h4_lsb = (int16_t)(buf[4] & 0x0F);
+  params->dig_h4 = dig_h4_msb | dig_h4_lsb;
+  int16_t dig_h5_msb = (int16_t)(int8_t)buf[5] * 16;
+  int16_t dig_h5_lsb = (int16_t)(buf[4] >> 4);
+  params->dig_h5 = dig_h5_msb | dig_h5_lsb;
+  params->dig_h6 = (int8_t)buf[6];
 }
 
 // Main Config for the sensor. Defined here so it can be use to inital configure
@@ -167,16 +143,17 @@ static void bme280_read_raw(bme280_config *config, int32_t *temp,
                             int32_t *pressure, int32_t *humidity) {
   // TODO: burst read 0xF7 0xFE
   // pressure 20 bit, temp 20 bit, humidity 16 bit
-  uint8_t buf[6];
+  uint8_t buf[8];
-  uint8_t reg = REG_PRESSURE_MSB;
+  uint8_t reg = 0xF7;
   i2c_write_blocking(config->i2c, ADDR, &reg, 1,
                      true); // true to keep master control of bus
-  i2c_read_blocking(config->i2c, ADDR, buf, 6,
+  i2c_read_blocking(config->i2c, ADDR, buf, 8,
                     false); // false - finished with bus
 
   // store the 20 bit read in a 32 bit signed integer for conversion
   *pressure = (buf[0] << 12) | (buf[1] << 4) | (buf[2] >> 4);
   *temp = (buf[3] << 12) | (buf[4] << 4) | (buf[5] >> 4);
+  *humidity = (buf[6] << 8) | buf[7];
 }
 
 static int32_t bme280_caculate_t_fine(bme280_config *config, int32_t temp) {
@@ -193,12 +170,12 @@ static int32_t bme280_caculate_t_fine(bme280_config *config, int32_t temp) {
   return var1 + var2;
 }
 
-float bme280_convert_temp(int32_t t_fine) {
+static float bme280_convert_temp(int32_t t_fine) {
   int32_t temp = (t_fine * 5 + 128) >> 8;
   return (float)temp / 100;
 }
 
-float bmp280_convert_pressure(bme280_config *config, int32_t t_fine,
+static float bme280_convert_pressure(bme280_config *config, int32_t t_fine,
                                      int32_t pressure) {
   bme280_compensation_params params = config->params;
   int32_t var1, var2;
@@ -230,6 +207,32 @@ float bmp280_convert_pressure(bme280_config *config, int32_t t_fine,
   return (float)converted / 100;
 }
 
+static float bmp280_convert_humidity(bme280_config *config, int32_t t_fine,
+                                     int32_t raw_humidity) {
+  double humidity_min = 0.0;
+  double humidity_max = 100.0;
+  double humidity, var1, var2, var3, var4, var5, var6;
+
+  bme280_compensation_params params = config->params;
+  var1 = ((double)t_fine) - 76800.0;
+  var2 = (((double)params.dig_h4) * 64.0 +
+          (((double)params.dig_h5) / 16384.0) * var1);
+  var3 = raw_humidity - var2;
+  var4 = ((double)params.dig_h2) / 65536.0;
+  var5 = (1.0 + (((double)params.dig_h3) / 67108864.0) * var1);
+  var6 = 1.0 + (((double)params.dig_h6) / 67108864.0) * var1 * var5;
+  var6 = var3 * var4 * (var5 * var6);
+  humidity = var6 * (1.0 - ((double)params.dig_h1) * var6 / 524288.0);
+
+  if (humidity > humidity_max) {
+    humidity = humidity_max;
+  } else if (humidity < humidity_min) {
+    humidity = humidity_min;
+  }
+
+  return (float)humidity;
+}
+
 bme280_reading bme280_read(bme280_config *config) {
   // instruct sensor to make a reading since we are in forced mode
   bme280_proc_sensor_read(config);
@@ -241,7 +244,7 @@ bme280_reading bme280_read(bme280_config *config) {
   bme280_reading reading;
   int32_t t_fine = bme280_caculate_t_fine(config, raw_temperature);
   reading.temperature = bme280_convert_temp(t_fine);
-  reading.pressure = bmp280_convert_pressure(config, t_fine, raw_pressure);
+  reading.pressure = bme280_convert_pressure(config, t_fine, raw_pressure);
-  reading.humidity = raw_humidity;
+  reading.humidity = bmp280_convert_humidity(config, t_fine, raw_humidity);
   return reading;
 }

bme280.h

@@ -19,11 +19,12 @@ typedef struct {
   int16_t dig_p9;
 
   // humidity params
-  uint16_t dig_h1;
+  uint8_t dig_h1;
   int16_t dig_h2;
-  int16_t dig_h3;
+  uint8_t dig_h3;
   int16_t dig_h4;
   int16_t dig_h5;
+  int8_t dig_h6;
 } bme280_compensation_params;
 
 typedef struct {
@@ -34,11 +35,11 @@ typedef struct {
 typedef struct {
   float temperature;
   float pressure;
-  int32_t humidity;
+  float humidity;
 } bme280_reading;
 
-void bme280_init(bme280_config *config, i2c_inst_t *i2c,
+void bme280_init(bme280_config *config, i2c_inst_t *i2c, uint8_t sda_pin,
-                                 uint8_t sda_pin, uint8_t scl_pin);
+                 uint8_t scl_pin);
 
 bme280_reading bme280_read(bme280_config *config);
 #endif /* BME280_H */

node1.c

@@ -16,6 +16,6 @@ int main() {
         current_reading = bme280_read(&config);
         printf("Tempature: %.2f\n", current_reading.temperature);
         printf("Pressure: %.2f\n", current_reading.pressure);
-        printf("Humidity: %d\n", current_reading.humidity);
+        printf("Humidity: %.2f\n", current_reading.humidity);
     }
 }