BMP280 library and example

2 files changed, 165 insertions, 127 deletions

diff --git a/lib/bmp280.c b/lib/bmp280.c
index 89cf4cf..0519cca 100644
--- a/lib/bmp280.c
+++ b/lib/bmp280.c
@@ -26,9 +26,6 @@
 #include <LUFA/Drivers/Peripheral/SPI.h>
 #include "bmp280.h"
 
-
-int32_t bmp280_t_fine = 0;
-
 void bmp280_cs(bmp280_sensor *sensor, uint8_t select)
 {
   if (!select)
@@ -37,115 +34,134 @@ void bmp280_cs(bmp280_sensor *sensor, uint8_t select)
     *(sensor->cs_port) &= ~ _BV(sensor->cs_pin);
 }
 
-void bmp280_write8(uint8_t reg, uint8_t value)
+void bmp280_write8(bmp280_sensor *sensor, uint8_t reg, uint8_t value)
 {
+  bmp280_cs(sensor, true);
   SPI_SendByte(reg & ~0x80); //bit 7 needs to be low for write mode
   SPI_SendByte(value);
+  bmp280_cs(sensor, false);
 }
 
-uint8_t bmp280_read8(uint8_t reg)
+uint8_t bmp280_read8(bmp280_sensor *sensor, uint8_t reg)
 {
+  bmp280_cs(sensor, true);
   SPI_SendByte(reg | 0x80); //bit 7 high for read mode
-  return SPI_ReceiveByte();
+  uint8_t value = SPI_ReceiveByte();
+  bmp280_cs(sensor, false);
+  return value;
 }
 
-uint16_t bmp280_read16(uint8_t reg)
+uint16_t bmp280_read16(bmp280_sensor *sensor, uint8_t reg)
 {
   uint16_t value = 0;
-   SPI_SendByte(reg | 0x80); //bit 7 high for read mode
-   value |= ((uint16_t) SPI_ReceiveByte() & 0xFF) << 8;
-   value |= (uint16_t) SPI_ReceiveByte() & 0xFF;
-   return value;
+  bmp280_cs(sensor, true);
+  SPI_SendByte(reg | 0x80); //bit 7 high for read mode
+  value |= ((uint16_t) SPI_ReceiveByte() & 0xFF) << 8;
+  value |= (uint16_t) SPI_ReceiveByte() & 0xFF;
+  bmp280_cs(sensor, false);
+  return value;
 }
 
-uint32_t bmp280_read24(uint8_t reg)
+uint32_t bmp280_read24(bmp280_sensor *sensor, uint8_t reg)
 {
-   uint32_t value = 0;
-   SPI_SendByte(reg | 0x80); //bit 7 high for read mode
-   value |= ((uint32_t) SPI_ReceiveByte() & 0xFF) << 16;
-   value |= ((uint32_t) SPI_ReceiveByte() & 0xFF) << 8;
-   value |= (uint32_t) SPI_ReceiveByte()  & 0xFF;
-   return value;
+  uint32_t value = 0;
+  bmp280_cs(sensor, true);
+  SPI_SendByte(reg | 0x80); //bit 7 high for read mode
+  value |= ((uint32_t) SPI_ReceiveByte() & 0xFF) << 16;
+  value |= ((uint32_t) SPI_ReceiveByte() & 0xFF) << 8;
+  value |= (uint32_t) SPI_ReceiveByte()  & 0xFF;
+  bmp280_cs(sensor, false);
+  return value;
 }
 
-int16_t bmp280_readS16(uint8_t reg)
+int16_t bmp280_readS16(bmp280_sensor *sensor, uint8_t reg)
 {
-  return (int16_t) bmp280_read16(reg);
+  return (int16_t) bmp280_read16(sensor, reg);
 }
 
-uint16_t bmp280_read16_LE(uint8_t reg)
+uint16_t bmp280_read16_LE(bmp280_sensor *sensor, uint8_t reg)
 {
-    uint16_t value = 0;
-   SPI_SendByte(reg | 0x80); //bit 7 high for read mode
-   value |= (uint16_t) SPI_ReceiveByte() & 0xFF;
-   value |= ((uint16_t) SPI_ReceiveByte() & 0xFF) << 8;
-   return value;
+  uint16_t value = bmp280_read16(sensor, reg);
+  return (value >> 8) | (value << 8);
 }
 
-int16_t bmp280_readS16_LE(uint8_t reg)
+int16_t bmp280_readS16_LE(bmp280_sensor *sensor, uint8_t reg)
 {
-  return (int16_t)bmp280_read16_LE(reg);
+  return (int16_t)bmp280_read16_LE(sensor, reg);
 }
 
 void bmp280_readCoefficients(bmp280_sensor *sensor)
 {
-  bmp280_cs(sensor, true);
-  sensor->dig_T1 = bmp280_read16_LE(BMP280_REGISTER_DIG_T1);
-  sensor->dig_T2 = bmp280_readS16_LE(BMP280_REGISTER_DIG_T2);
-  sensor->dig_T3 = bmp280_readS16_LE(BMP280_REGISTER_DIG_T3);
-  sensor->dig_P1 = bmp280_read16_LE(BMP280_REGISTER_DIG_P1);
-  sensor->dig_P2 = bmp280_readS16_LE(BMP280_REGISTER_DIG_P2);
-  sensor->dig_P3 = bmp280_readS16_LE(BMP280_REGISTER_DIG_P3);
-  sensor->dig_P4 = bmp280_readS16_LE(BMP280_REGISTER_DIG_P4);
-  sensor->dig_P5 = bmp280_readS16_LE(BMP280_REGISTER_DIG_P5);
-  sensor->dig_P6 = bmp280_readS16_LE(BMP280_REGISTER_DIG_P6);
-  sensor->dig_P7 = bmp280_readS16_LE(BMP280_REGISTER_DIG_P7);
-  sensor->dig_P8 = bmp280_readS16_LE(BMP280_REGISTER_DIG_P8);
-  sensor->dig_P9 = bmp280_readS16_LE(BMP280_REGISTER_DIG_P9);
-  bmp280_cs(sensor, false);  
+  sensor->dig_T1 = bmp280_read16_LE(sensor,BMP280_REGISTER_DIG_T1);
+  sensor->dig_T2 = bmp280_readS16_LE(sensor,BMP280_REGISTER_DIG_T2);
+  sensor->dig_T3 = bmp280_readS16_LE(sensor,BMP280_REGISTER_DIG_T3);
+  sensor->dig_P1 = bmp280_read16_LE(sensor,BMP280_REGISTER_DIG_P1);
+  sensor->dig_P2 = bmp280_readS16_LE(sensor,BMP280_REGISTER_DIG_P2);
+  sensor->dig_P3 = bmp280_readS16_LE(sensor,BMP280_REGISTER_DIG_P3);
+  sensor->dig_P4 = bmp280_readS16_LE(sensor,BMP280_REGISTER_DIG_P4);
+  sensor->dig_P5 = bmp280_readS16_LE(sensor,BMP280_REGISTER_DIG_P5);
+  sensor->dig_P6 = bmp280_readS16_LE(sensor,BMP280_REGISTER_DIG_P6);
+  sensor->dig_P7 = bmp280_readS16_LE(sensor,BMP280_REGISTER_DIG_P7);
+  sensor->dig_P8 = bmp280_readS16_LE(sensor,BMP280_REGISTER_DIG_P8);
+  sensor->dig_P9 = bmp280_readS16_LE(sensor,BMP280_REGISTER_DIG_P9);
+}
+
+uint8_t bmp280_check_chipid(bmp280_sensor *sensor)
+{
+  uint8_t chip_id = bmp280_read8(sensor, BMP280_REGISTER_CHIPID);
+  return chip_id == 0x58;  
 }
 
 //need to init SPI beforehand
-void bmp280_init(bmp280_sensor *sensor, volatile uint8_t *cs_port, uint8_t cs_pin)
+uint8_t bmp280_init(bmp280_sensor *sensor, volatile uint8_t *cs_port, uint8_t cs_pin)
 {
   memset(sensor,0,sizeof(bmp280_sensor));
   sensor->cs_port = cs_port;
   sensor->cs_pin = cs_pin;
+  uint8_t sensor_available = bmp280_check_chipid(sensor);
+  if (!sensor_available)
+    return sensor_available; //don't talk with chip, it doesn't speak our language
   bmp280_readCoefficients(sensor);
+  bmp280_write8(sensor, BMP280_REGISTER_CONTROL, 0x3F);
+  return sensor_available;
 }
 
-float bmp280_readTemp(bmp280_sensor *sensor)
+int32_t bmp280_readFineTemp(bmp280_sensor *sensor)
 {
   int32_t var1, var2;
 
-  bmp280_cs(sensor, true);
-  int32_t adc_T = bmp280_read24(BMP280_REGISTER_TEMPDATA);
-  bmp280_cs(sensor, false);
+  int32_t adc_T = bmp280_read24(sensor, BMP280_REGISTER_TEMPDATA);
   adc_T >>= 4;
 
-  var1  = ((((adc_T>>3) - ((int32_t)sensor->dig_T1 <<1))) *
-     ((int32_t)sensor->dig_T2)) >> 11;
+  var1  = ((((adc_T>>3) - ((int32_t)sensor->dig_T1 <<1))) * ((int32_t)sensor->dig_T2)) >> 11;
+  var2  = (((((adc_T>>4) - ((int32_t)sensor->dig_T1)) * ((adc_T>>4) - ((int32_t)sensor->dig_T1))) >> 12) * ((int32_t)sensor->dig_T3)) >> 14;
 
-  var2  = (((((adc_T>>4) - ((int32_t)sensor->dig_T1)) *
-       ((adc_T>>4) - ((int32_t)sensor->dig_T1))) >> 12) *
-     ((int32_t)sensor->dig_T3)) >> 14;
-
-  bmp280_t_fine = var1 + var2;
+  return var1 + var2;
+}
 
+float bmp280_convertTempToCelsius(int32_t bmp280_t_fine)
+{
   float T  = (bmp280_t_fine * 5 + 128) >> 8;
   return T/100;
 }
 
-float bmp280_readPressure(bmp280_sensor *sensor)
+float bmp280_readTemp(bmp280_sensor *sensor)
 {
+  return bmp280_convertTempToCelsius(bmp280_readFineTemp(sensor));
+}
+
+bmp280_result bmp280_readTempAndPressure(bmp280_sensor *sensor)
+{
+  bmp280_result result;
+  result.temperature = 0;
+  result.pressure = 0;
+
   int64_t var1, var2, p;
 
-  // Must be done first to get the bmp280_t_fine variable
-  bmp280_readTemp(sensor);
+  int32_t bmp280_t_fine = bmp280_readFineTemp(sensor);
+  result.temperature = bmp280_convertTempToCelsius(bmp280_t_fine);
 
-  bmp280_cs(sensor, true);
-  int32_t adc_P = bmp280_read24(BMP280_REGISTER_PRESSUREDATA);
-  bmp280_cs(sensor, false);
+  int32_t adc_P = bmp280_read24(sensor, BMP280_REGISTER_PRESSUREDATA);
   adc_P >>= 4;
 
   var1 = ((int64_t)bmp280_t_fine) - 128000;
@@ -158,7 +174,7 @@ float bmp280_readPressure(bmp280_sensor *sensor)
 
   if (var1 == 0)
   {
-    return 0;  // avoid exception caused by division by zero
+    return result;  // avoid exception caused by division by zero
   }
   p = 1048576 - adc_P;
   p = (((p<<31) - var2)*3125) / var1;
@@ -166,20 +182,26 @@ float bmp280_readPressure(bmp280_sensor *sensor)
   var2 = (((int64_t)sensor->dig_P8) * p) >> 19;
 
   p = ((p + var1 + var2) >> 8) + (((int64_t)sensor->dig_P7)<<4);
-  return (float)p/256;
+  result.pressure = (float)p/256;
+  return result;
 }
 
-/*float bmp280_readAltitude(bmp280_sensor *sensor, float sealevelp)
+float bmp280_readPressure(bmp280_sensor *sensor)
 {
-  float altitude;
+  bmp280_result result = bmp280_readTempAndPressure(sensor);
+  return result.pressure;
+}
 
-  float pressure = bmp280_readPressure(sensor); // in Si units for Pascal
+float bmp280_calcAltitude(float pressure, float sealevelp)
+{
   pressure /= 100;
+  return 44330 * (1.0 - pow(pressure / sealevelp, 0.1903));
+}
 
-  altitude = 44330 * (1.0 - pow(pressure / seaLevelhPa, 0.1903));
-
-  return altitude;
-}*/
+float bmp280_readAltitude(bmp280_sensor *sensor, float sealevelp)
+{
+  return bmp280_calcAltitude(bmp280_readTempAndPressure(sensor).pressure, sealevelp);
+}
 
 
 /// Helper Functions
diff --git a/lib/bmp280.h b/lib/bmp280.h
index 22472e3..fe8435e 100644
--- a/lib/bmp280.h
+++ b/lib/bmp280.h
@@ -29,78 +29,94 @@ extern "C" {
 #endif
 
 #define BMP280_AVERAGE_SEA_LEVEL_PRESSURE 1013.25
-#define BMP280_LUFA_SPIO_OPTIONS SPI_SPEED_FCPU_DIV_16  | SPI_MODE_MASTER | SPI_ORDER_MSB_FIRST | SPI_SCK_LEAD_RISING | SPI_SAMPLE_LEADING
+#define BMP280_LUFA_SPIO_OPTIONS SPI_SPEED_FCPU_DIV_32  | SPI_MODE_MASTER | SPI_ORDER_MSB_FIRST | SPI_SCK_LEAD_RISING | SPI_SAMPLE_LEADING
 
 /*=========================================================================
-    REGISTERS
-    -----------------------------------------------------------------------*/
-    enum
-    {
-      BMP280_REGISTER_DIG_T1              = 0x88,
-      BMP280_REGISTER_DIG_T2              = 0x8A,
-      BMP280_REGISTER_DIG_T3              = 0x8C,
-
-      BMP280_REGISTER_DIG_P1              = 0x8E,
-      BMP280_REGISTER_DIG_P2              = 0x90,
-      BMP280_REGISTER_DIG_P3              = 0x92,
-      BMP280_REGISTER_DIG_P4              = 0x94,
-      BMP280_REGISTER_DIG_P5              = 0x96,
-      BMP280_REGISTER_DIG_P6              = 0x98,
-      BMP280_REGISTER_DIG_P7              = 0x9A,
-      BMP280_REGISTER_DIG_P8              = 0x9C,
-      BMP280_REGISTER_DIG_P9              = 0x9E,
-
-      BMP280_REGISTER_CHIPID             = 0xD0,
-      BMP280_REGISTER_VERSION            = 0xD1,
-      BMP280_REGISTER_SOFTRESET          = 0xE0,
-
-      BMP280_REGISTER_CAL26              = 0xE1,  // R calibration stored in 0xE1-0xF0
-
-      BMP280_REGISTER_CONTROL            = 0xF4,
-      BMP280_REGISTER_CONFIG             = 0xF5,
-      BMP280_REGISTER_PRESSUREDATA       = 0xF7,
-      BMP280_REGISTER_TEMPDATA           = 0xFA,
-    };
+REGISTERS
+-----------------------------------------------------------------------*/
+enum
+{
+  BMP280_REGISTER_DIG_T1              = 0x88,
+  BMP280_REGISTER_DIG_T2              = 0x8A,
+  BMP280_REGISTER_DIG_T3              = 0x8C,
+
+  BMP280_REGISTER_DIG_P1              = 0x8E,
+  BMP280_REGISTER_DIG_P2              = 0x90,
+  BMP280_REGISTER_DIG_P3              = 0x92,
+  BMP280_REGISTER_DIG_P4              = 0x94,
+  BMP280_REGISTER_DIG_P5              = 0x96,
+  BMP280_REGISTER_DIG_P6              = 0x98,
+  BMP280_REGISTER_DIG_P7              = 0x9A,
+  BMP280_REGISTER_DIG_P8              = 0x9C,
+  BMP280_REGISTER_DIG_P9              = 0x9E,
+
+  BMP280_REGISTER_CHIPID             = 0xD0,
+  BMP280_REGISTER_VERSION            = 0xD1,
+  BMP280_REGISTER_SOFTRESET          = 0xE0,
+
+  BMP280_REGISTER_CAL26              = 0xE1,  // R calibration stored in 0xE1-0xF0
+
+  BMP280_REGISTER_CONTROL            = 0xF4,
+  BMP280_REGISTER_CONFIG             = 0xF5,
+  BMP280_REGISTER_PRESSUREDATA       = 0xF7,
+  BMP280_REGISTER_TEMPDATA           = 0xFA,
+};
 
 /*=========================================================================*/
 
 
 /*=========================================================================
-    CALIBRATION DATA
-    -----------------------------------------------------------------------*/
-    typedef struct
-    {
-      volatile uint8_t *cs_port;
-      uint8_t  cs_pin;
-      uint16_t dig_T1;
-      int16_t  dig_T2;
-      int16_t  dig_T3;
-
-      uint16_t dig_P1;
-      int16_t  dig_P2;
-      int16_t  dig_P3;
-      int16_t  dig_P4;
-      int16_t  dig_P5;
-      int16_t  dig_P6;
-      int16_t  dig_P7;
-      int16_t  dig_P8;
-      int16_t  dig_P9;
-
-      uint8_t  dig_H1;
-      int16_t  dig_H2;
-      uint8_t  dig_H3;
-      int16_t  dig_H4;
-      int16_t  dig_H5;
-      int8_t   dig_H6;
-    } bmp280_sensor;
+CALIBRATION DATA
+-----------------------------------------------------------------------*/
+typedef struct
+{
+  volatile uint8_t *cs_port;
+  uint8_t  cs_pin;
+
+  uint16_t dig_T1;
+  int16_t  dig_T2;
+  int16_t  dig_T3;
+
+  uint16_t dig_P1;
+  int16_t  dig_P2;
+  int16_t  dig_P3;
+  int16_t  dig_P4;
+  int16_t  dig_P5;
+  int16_t  dig_P6;
+  int16_t  dig_P7;
+  int16_t  dig_P8;
+  int16_t  dig_P9;
+
+  uint8_t  dig_H1;
+  int16_t  dig_H2;
+  uint8_t  dig_H3;
+  int16_t  dig_H4;
+  int16_t  dig_H5;
+  int8_t   dig_H6;
+} bmp280_sensor;
 /*=========================================================================*/
 
+typedef struct
+{
+  float temperature;
+  float pressure;
+} bmp280_result;
+
 
 //make sure to configure the cs_pin as OUTPUT beforehand
 //make sure to configure SPI beforehand
-void bmp280_init(bmp280_sensor *sensor, volatile uint8_t *cs_port, uint8_t cs_pin);
+uint8_t bmp280_init(bmp280_sensor *sensor, volatile uint8_t *cs_port, uint8_t cs_pin);
+//check if we deal with am bmp280 chip
+uint8_t bmp280_check_chipid(bmp280_sensor *sensor);
+//returns temperature in degress celsius
 float bmp280_readTemp(bmp280_sensor *sensor);
+//returns ambient pressure in pascal
 float bmp280_readPressure(bmp280_sensor *sensor);
+//read Temperature and Pressure in one fell swoop
+bmp280_result bmp280_readTempAndPressure(bmp280_sensor *sensor);
+//calculate altitude from measured pressure and given sealevel-pressure
+float bmp280_calcAltitude(float pressure, float sealevelp);
+//readPressure and calculate altitude
 float bmp280_readAltitude(bmp280_sensor *sensor, float sealevelp);