Joel Pallent
sensor
Diff: BME280.cpp
- Revision:
- 0:ade9be832910
- Child:
- 1:763a4018aaec
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/BME280.cpp Mon Apr 06 09:13:00 2015 +0000
@@ -0,0 +1,195 @@
+#include "mbed.h"
+#include "BME280.h"
+
+BME280::BME280(PinName sda, PinName scl, char slave_adr)
+ :
+ i2c_p(new I2C(sda, scl)),
+ i2c(*i2c_p),
+ address(slave_adr),
+ t_fine(0)
+{
+ initialize();
+}
+
+BME280::BME280(I2C &i2c_obj, char slave_adr)
+ :
+ i2c_p(NULL),
+ i2c(i2c_obj),
+ address(slave_adr),
+ t_fine(0)
+{
+ initialize();
+}
+
+BME280::~BME280()
+{
+ if (NULL != i2c_p)
+ delete i2c_p;
+}
+
+void BME280::initialize()
+{
+ char cmd[18];
+
+ cmd[0] = 0xf2; // ctrl_hum
+ cmd[1] = 0x01; // Humidity oversampling x1
+ i2c.write(address, cmd, 2);
+
+ cmd[0] = 0xf4; // ctrl_meas
+ cmd[1] = 0x27; // Temparature oversampling x1, Pressure oversampling x1, Normal mode
+ i2c.write(address, cmd, 2);
+
+ cmd[0] = 0xf5; // config
+ cmd[1] = 0xa0; // Standby 1000ms, Filter off
+ i2c.write(address, cmd, 2);
+
+ cmd[0] = 0x88; // read dig_T regs
+ i2c.write(address, cmd, 1);
+ i2c.read(address, cmd, 6);
+
+ dig_T1 = (cmd[1] << 8) | cmd[0];
+ dig_T2 = (cmd[3] << 8) | cmd[2];
+ dig_T3 = (cmd[5] << 8) | cmd[4];
+
+ DEBUG_PRINT("dig_T = 0x%x, 0x%x, 0x%x\n", dig_T1, dig_T2, dig_T3);
+
+ cmd[0] = 0x8E; // read dig_P regs
+ i2c.write(address, cmd, 1);
+ i2c.read(address, cmd, 18);
+
+ dig_P1 = (cmd[ 1] << 8) | cmd[ 0];
+ dig_P2 = (cmd[ 3] << 8) | cmd[ 2];
+ dig_P3 = (cmd[ 5] << 8) | cmd[ 4];
+ dig_P4 = (cmd[ 7] << 8) | cmd[ 6];
+ dig_P5 = (cmd[ 9] << 8) | cmd[ 8];
+ dig_P6 = (cmd[11] << 8) | cmd[10];
+ dig_P7 = (cmd[13] << 8) | cmd[12];
+ dig_P8 = (cmd[15] << 8) | cmd[14];
+ dig_P9 = (cmd[17] << 8) | cmd[16];
+
+ DEBUG_PRINT("dig_P = 0x%x, 0x%x, 0x%x, 0x%x, 0x%x, 0x%x, 0x%x, 0x%x, 0x%x\n", dig_P1, dig_P2, dig_P3, dig_P4, dig_P5, dig_P6, dig_P7, dig_P8, dig_P9);
+
+ cmd[0] = 0xA1; // read dig_H regs
+ i2c.write(address, cmd, 1);
+ i2c.read(address, cmd, 9);
+
+ dig_H1 = cmd[0];
+ dig_H2 = (cmd[2] << 8) | cmd[1];
+ dig_H3 = cmd[3];
+ dig_H4 = (cmd[4] << 4) | (cmd[5] & 0x0f);
+ dig_H5 = (cmd[7] << 4) | ((cmd[6]>>4) & 0x0f);
+ dig_H6 = cmd[8];
+
+ DEBUG_PRINT("dig_H = 0x%x, 0x%x, 0x%x, 0x%x, 0x%x, 0x%x\n", dig_H1, dig_H2, dig_H3, dig_H4, dig_H5, dig_H6);
+}
+
+float BME280::getTemperature()
+{
+ uint32_t temp_raw;
+ float tempf;
+ char cmd[4];
+
+ cmd[0] = 0xfa; // temp_msb
+ i2c.write(address, cmd, 1);
+ i2c.read(address, &cmd[1], 1);
+
+ cmd[0] = 0xfb; // temp_lsb
+ i2c.write(address, cmd, 1);
+ i2c.read(address, &cmd[2], 1);
+
+ cmd[0] = 0xfc; // temp_xlsb
+ i2c.write(address, cmd, 1);
+ i2c.read(address, &cmd[3], 1);
+
+ temp_raw = (cmd[1] << 12) | (cmd[2] << 4) | (cmd[3] >> 4);
+
+ int32_t temp;
+
+ temp =
+ (((((temp_raw >> 3) - (dig_T1 << 1))) * dig_T2) >> 11) +
+ ((((((temp_raw >> 4) - dig_T1) * ((temp_raw >> 4) - dig_T1)) >> 12) * dig_T3) >> 14);
+
+ t_fine = temp;
+ temp = (temp * 5 + 128) >> 8;
+ tempf = (float)temp;
+
+ return (tempf/100.0f);
+}
+
+float BME280::getPressure()
+{
+ uint32_t press_raw;
+ float pressf;
+ char cmd[4];
+
+ cmd[0] = 0xf7; // press_msb
+ i2c.write(address, cmd, 1);
+ i2c.read(address, &cmd[1], 1);
+
+ cmd[0] = 0xf8; // press_lsb
+ i2c.write(address, cmd, 1);
+ i2c.read(address, &cmd[2], 1);
+
+ cmd[0] = 0xf9; // press_xlsb
+ i2c.write(address, cmd, 1);
+ i2c.read(address, &cmd[3], 1);
+
+ press_raw = (cmd[1] << 12) | (cmd[2] << 4) | (cmd[3] >> 4);
+
+ int32_t var1, var2;
+ uint32_t press;
+
+ var1 = (t_fine >> 1) - 64000;
+ var2 = (((var1 >> 2) * (var1 >> 2)) >> 11) * dig_P6;
+ var2 = var2 + ((var1 * dig_P5) << 1);
+ var2 = (var2 >> 2) + (dig_P4 << 16);
+ var1 = (((dig_P3 * (((var1 >> 2)*(var1 >> 2)) >> 13)) >> 3) + ((dig_P2 * var1) >> 1)) >> 18;
+ var1 = ((32768 + var1) * dig_P1) >> 15;
+ if (var1 == 0) {
+ return 0;
+ }
+ press = (((1048576 - press_raw) - (var2 >> 12))) * 3125;
+ if(press < 0x80000000) {
+ press = (press << 1) / var1;
+ } else {
+ press = (press / var1) * 2;
+ }
+ var1 = ((int32_t)dig_P9 * ((int32_t)(((press >> 3) * (press >> 3)) >> 13))) >> 12;
+ var2 = (((int32_t)(press >> 2)) * (int32_t)dig_P8) >> 13;
+ press = (press + ((var1 + var2 + dig_P7) >> 4));
+
+ pressf = (float)press;
+ return (pressf/100.0f);
+}
+
+float BME280::getHumidity()
+{
+ uint32_t hum_raw;
+ float humf;
+ char cmd[4];
+
+ cmd[0] = 0xfd; // hum_msb
+ i2c.write(address, cmd, 1);
+ i2c.read(address, &cmd[1], 1);
+
+ cmd[0] = 0xfd; // hum_lsb
+ i2c.write(address, cmd, 1);
+ i2c.read(address, &cmd[2], 1);
+
+ hum_raw = (cmd[1] << 8) | cmd[2];
+
+ int32_t v_x1;
+
+ v_x1 = t_fine - 76800;
+ v_x1 = (((((hum_raw << 14) -(((int32_t)dig_H4) << 20) - (((int32_t)dig_H5) * v_x1)) +
+ ((int32_t)16384)) >> 15) * (((((((v_x1 * (int32_t)dig_H6) >> 10) *
+ (((v_x1 * ((int32_t)dig_H3)) >> 11) + 32768)) >> 10) + 2097152) *
+ (int32_t)dig_H2 + 8192) >> 14));
+ v_x1 = (v_x1 - (((((v_x1 >> 15) * (v_x1 >> 15)) >> 7) * (int32_t)dig_H1) >> 4));
+ v_x1 = (v_x1 < 0 ? 0 : v_x1);
+ v_x1 = (v_x1 > 419430400 ? 419430400 : v_x1);
+
+ humf = (float)(v_x1 >> 12);
+
+ return (humf/1024.0f);
+}