switch bme280 to forced mode

bme280.c

@@ -18,6 +18,11 @@
    https://shop.pimoroni.com/products/bme280-breakout?variant=29420960677971
         - pimoroni pico sdk
    https://github.com/boschsensortec/BME280_SensorAPI/tree/c47f06eb44fc96970f0abfcc941ec16425b2a9e6
+
+   Suggested Settings:
+    - forced mode at 1 sample per min
+    - oversampling * 1 on temp, humidity, and pressure
+    - IIR Filter off
 */
 
 // Define the custom pins for I2C
@@ -73,7 +78,8 @@
 // 17 * 2  = 34
 #define NUM_COMPENSATION_PARAMS 34
 
-static void bmp280_get_compensation_params(i2c_inst_t *i2c, bme280_compensation_params *params) {
+static void bmp280_get_compensation_params(i2c_inst_t *i2c,
+                                           bme280_compensation_params *params) {
   // raw temp and pressure values need to be calibrated according to
   // parameters generated during the manufacturing of the sensor
   // there are 3 temperature params, and 9 pressure params, each with a LSB
@@ -109,6 +115,10 @@ static void bmp280_get_compensation_params(i2c_inst_t *i2c, bme280_compensation_
   params->dig_h5 = (int16_t)(buf[33] << 8) | buf[32];
 }
 
+// Main Config for the sensor. Defined here so it can be use to inital configure the sensor and to proc further reads
+// 001 sets osrs_t temp over sampling to 1, 001 sets osrs_p pressure
+// oversampling to 1, 01 sets sensor mode to forced
+static const uint8_t main_config = 0b00100101;
 void bme280_init(bme280_config *config, i2c_inst_t *i2c, uint8_t sda_pin,
                  uint8_t scl_pin) {
   i2c_init(i2c, 100 * 1000);
@@ -116,24 +126,25 @@ void bme280_init(bme280_config *config, i2c_inst_t *i2c, uint8_t sda_pin,
   gpio_set_function(scl_pin, GPIO_FUNC_I2C);
   gpio_pull_up(sda_pin);
   gpio_pull_up(scl_pin);
-  // use the "handheld device dynamic" optimal setting (see datasheet)
-  // bi_decl(bi_2pins_with_func(sda_pin, scl_pin, GPIO_FUNC_I2C));
-  // bi_decl(bi_program_description("BMP280 I2C LIB"));
 
   uint8_t buf[2];
 
-  // 500ms sampling time, x16 filter
+  // 000 for t_sb is normal mode sample rate n/a, 000 turns filter off, 0 turns
-  const uint8_t reg_config_val = ((0x04 << 5) | (0x05 << 2)) & 0xFC;
+  // off spi
-
+  buf[0] = 0xF5; // config
-  // send register number followed by its corresponding value
+  buf[1] = 0x00; // all zeros
-  buf[0] = REG_CONFIG;
-  buf[1] = reg_config_val;
   i2c_write_blocking(i2c, ADDR, buf, 2, false);
 
-  // osrs_t x1, osrs_p x4, normal mode operation
+  // send humidity oversample config
-  const uint8_t reg_ctrl_meas_val = (0x01 << 5) | (0x03 << 2) | (0x03);
+  // 001 at the end sets over sampling to 1
-  buf[0] = REG_CTRL_MEAS;
+  const uint8_t humidity_config = 0b00000001;
-  buf[1] = reg_ctrl_meas_val;
+  buf[0] = 0xF2; // ctrl_hum
+  buf[1] = humidity_config;
+  i2c_write_blocking(i2c, ADDR, buf, 2, false);
+
+  // send temp oversample, pressure oversample, and mode configs
+  buf[0] = 0xF4; // ctrl_meas
+  buf[1] = main_config;
   i2c_write_blocking(i2c, ADDR, buf, 2, false);
 
   bme280_compensation_params params;
@@ -144,28 +155,58 @@ void bme280_init(bme280_config *config, i2c_inst_t *i2c, uint8_t sda_pin,
   return;
 }
 
-static void bmp280_read_raw(bme280_config *config, int32_t* temp, int32_t* pressure, int32_t* humidity) {
+/**
-    // BMP280 data registers are auto-incrementing and we have 3 temperature and
+ *Instructs the BME280 sensor to take a measurement in forced mode.
-    // pressure registers each, so we start at 0xF7 and read 6 bytes to 0xFC
+ */
-    // note: normal mode does not require further ctrl_meas and config register writes
+static void bme280_proc_sensor_read(bme280_config *config) {
+  uint8_t buf[2] = {0xF4, main_config};
+  i2c_write_blocking(config->i2c, ADDR, buf, 2, false);
+}
 
+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 reg = REG_PRESSURE_MSB;
-    i2c_write_blocking(config->i2c, ADDR, &reg, 1, true);  // true to keep master control of bus
+  i2c_write_blocking(config->i2c, ADDR, &reg, 1,
-    i2c_read_blocking(config->i2c, ADDR, buf, 6, false);  // false - finished with bus
+                     true); // true to keep master control of bus
+  i2c_read_blocking(config->i2c, ADDR, buf, 6,
+                    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);
 }
 
+float bmp280_convert_temp(bme280_config *config, int32_t temp) {
+  bme280_compensation_params params = config->params;
+  int32_t var1, var2;
+  var1 = ((((temp >> 3) - ((int32_t)params.dig_t1 << 1))) *
+          ((int32_t)params.dig_t2)) >>
+         11;
+  var2 = (((((temp >> 4) - ((int32_t)params.dig_t1)) *
+            ((temp >> 4) - ((int32_t)params.dig_t1))) >>
+           12) *
+          ((int32_t)params.dig_t3)) >>
+         14;
+  int32_t var3 = var1 + var2;
+  // uses the BMP280 calibration parameters to compensate the temperature value
+  // read from its registers
+  int32_t var4 = (var3 * 5 + 128) >> 8;
+  return (float)var4 / 100;
+}
+
 bme280_reading bme280_read(bme280_config *config) {
+  // instruct sensor to make a reading since we are in forced mode
+  bme280_proc_sensor_read(config);
+
   int32_t raw_temperature = 0;
   int32_t raw_pressure = 0;
   int32_t raw_humidity = 0;
-    bmp280_read_raw(config, &raw_temperature, &raw_pressure, &raw_humidity);
+  bme280_read_raw(config, &raw_temperature, &raw_pressure, &raw_humidity);
   bme280_reading reading;
-    reading.temperature = raw_temperature;
+  reading.temperature = bmp280_convert_temp(config, raw_temperature);
   reading.pressure = raw_pressure;
   reading.humidity = raw_humidity;
   return reading;

bme280.h

@@ -32,7 +32,7 @@ typedef struct {
 } bme280_config;
 
 typedef struct {
-  int32_t temperature;
+  float temperature;
   int32_t pressure;
   int32_t humidity;
 } bme280_reading;

node1.c

@@ -11,10 +11,10 @@ int main() {
     bme280_init(&config, i2c1, 14, 15);
     bme280_reading current_reading;
     while (true) {
-        sleep_ms(2500);
+        sleep_ms(5000); // wait 5 sec
         printf("Making reading\n");
         current_reading = bme280_read(&config);
-        printf("Tempature: %d\n", current_reading.temperature);
+        printf("Tempature: %.2f\n", current_reading.temperature);
         printf("Pressure: %d\n", current_reading.pressure);
         printf("Humidity: %d\n", current_reading.humidity);
     }