Diff: BMP280_SPI.cpp

Revision:

0:0463be4e35c0

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/BMP280_SPI.cpp	Thu Feb 08 09:56:31 2018 +0000
@@ -0,0 +1,163 @@
+/**
+ ******************************************************************************
+ * @file    BMP280_SPI.cpp
+ * @author  Toyomasa Watarai
+ * @version V1.0.0
+ * @date    8 Feb 2018
+ * @brief   BMP280_SPI class implementation
+ ******************************************************************************
+ * @attention
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "mbed.h"
+#include "BMP280_SPI.h"
+
+BMP280_SPI::BMP280_SPI(PinName mosi, PinName miso, PinName sclk, PinName cs)
+    :
+    _spi(mosi, miso, sclk),
+    _cs(cs),
+    t_fine(0)
+{
+    initialize();
+}
+
+
+BMP280_SPI::~BMP280_SPI()
+{
+}
+
+void BMP280_SPI::initialize()
+{
+    char cmd[18];
+
+    _cs = 1;
+    _spi.format(8, 0); // 8-bit, mode=0
+    _spi.frequency(1000000); // 1MHZ
+
+    _cs = 0;
+    _spi.write(0xd0); // read chip_id
+    cmd[0] = _spi.write(0); // read chip_id
+    _cs = 1;
+    
+    DEBUG_PRINT("chip_id = 0x%x\n", cmd[0]);
+
+    _cs = 0;
+    _spi.write(0xf4 & BMP280_SPI_WRITE); // ctrl_meas
+    _spi.write((3<<5) | (3<<2) | 3); // Temparature oversampling x4, Pressure oversampling x4, Normal mode
+    _cs = 1;
+
+    _cs = 0;
+    _spi.write(0xf5 & BMP280_SPI_WRITE); // config
+    _spi.write((5<<5) | (0<<2) | 0); // Standby 1000ms, Filter off, 4-wire SPI interface
+    _cs = 1;
+
+    wait(1);
+    
+    _cs = 0;
+    _spi.write(0x88); // read dig_T regs
+    for(int i = 0; i < 6; i++)
+        cmd[i] = _spi.write(0);
+    _cs = 1;
+
+    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);
+    DEBUG_PRINT("dig_T = %d, %d, %d\n", dig_T1, dig_T2, dig_T3);
+
+    _cs = 0;
+    _spi.write(0x8e); // read dig_P regs
+    for(int i = 0; i < 18; i++)
+        cmd[i] = _spi.write(0);
+    _cs = 1;
+
+    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);
+    DEBUG_PRINT("dig_P = %d, %d, %d, %d, %d, %d, %d, %d, %d\n", dig_P1, dig_P2, dig_P3, dig_P4, dig_P5, dig_P6, dig_P7, dig_P8, dig_P9);
+
+}
+
+float BMP280_SPI::getTemperature()
+{
+    int32_t temp_raw, var1, var2, temp;
+    float tempf;
+    char cmd[3];
+
+    _cs = 0;
+    _spi.write(0xfa);
+    for(int i = 0; i < 3; i++)
+        cmd[i] = _spi.write(0);
+    _cs = 1;
+
+    temp_raw = (cmd[0] << 12) | (cmd[1] << 4) | (cmd[2] >> 4);
+
+    var1 = ((((temp_raw >> 3) - (dig_T1 << 1))) * dig_T2) >> 11;
+    var2 = (((((temp_raw >> 4) - dig_T1) * ((temp_raw >> 4) - dig_T1)) >> 12) * dig_T3) >> 14;
+
+    t_fine = var1 + var2;
+    temp = (t_fine * 5 + 128) >> 8;
+    tempf = (float)temp;
+
+    return (tempf/100.0f);
+}
+
+float BMP280_SPI::getPressure()
+{
+    int32_t press_raw;
+    float pressf;
+    char cmd[3];
+
+    _cs = 0;
+    _spi.write(0xf7); // press_msb
+    for(int i = 0; i < 3; i++)
+        cmd[i] = _spi.write(0);
+    _cs = 1;
+
+    press_raw = (cmd[0] << 12) | (cmd[1] << 4) | (cmd[2] >> 4);
+
+    int64_t var1, var2, p;
+    uint32_t press;
+
+    var1 = (int64_t)t_fine - 128000;
+    var2 = var1 * var1 * (int64_t)dig_P6;
+    var2 = var2 + ((var1 * (int64_t)dig_P5) << 17);
+    var2 = var2 + ((int64_t)dig_P4 << 35);
+    var1 = ((var1 * var1 * (int64_t)dig_P3)>>8) + ((var1 * (int64_t)dig_P2)<<12);
+    var1 = (((((int64_t)1)<<47)+var1))*((int64_t)dig_P1)>>33;
+    
+    if (var1 == 0) {
+        return 0;
+    }
+    p = 1048576 - press_raw;
+    p = (((p<<31)-var2)*3125)/var1;
+    var1 = (((int64_t)dig_P9) * (p>>13) * (p>>13)) >> 25;
+    var2 = (((int64_t)dig_P8) * p) >> 19;
+    p = ((p + var1 + var2) >> 8) + (((int64_t)dig_P7)<<4);
+    press = (uint32_t)p/256;
+
+    pressf = (float)press;
+    return (pressf/100.0f);
+}
+