Diff: LPS.cpp

Revision:

0:4ea758df868a

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/LPS.cpp	Sat Dec 22 16:44:40 2018 +0000
@@ -0,0 +1,212 @@
+#include "LPS.h"
+#include "mbed.h"
+
+// Defines ///////////////////////////////////////////////////////////
+
+// The Arduino two-wire interface uses a 7-bit number for the address,
+#define SA0_LOW_ADDRESS  0b1011100
+#define SA0_HIGH_ADDRESS 0b1011101
+
+#define TEST_REG_NACK -1
+
+#define LPS331AP_WHO_ID 0xBB
+#define LPS25H_WHO_ID   0xBD
+
+// Constructors //////////////////////////////////////////////////////
+
+LPS::LPS(I2C& p_i2c):_i2c(p_i2c)
+{
+    _device = device_auto;
+  
+    // Pololu board pulls SA0 high, so default assumption is that it is
+    // high
+    address = SA0_HIGH_ADDRESS;
+}
+
+// Public Methods ////////////////////////////////////////////////////
+
+// sets or detects device type and slave address; returns bool indicating success
+bool LPS::init(deviceType device, uint8_t sa0)
+{
+    if (!detectDeviceAndAddress(device, (sa0State)sa0))
+        return false;
+    
+    switch (_device)
+    {
+        case device_25H:
+        translated_regs[-INTERRUPT_CFG] = LPS25H_INTERRUPT_CFG;
+        translated_regs[-INT_SOURCE]    = LPS25H_INT_SOURCE;
+        translated_regs[-THS_P_L]       = LPS25H_THS_P_L;
+        translated_regs[-THS_P_H]       = LPS25H_THS_P_H;
+        return true;
+        break;
+      
+        case device_331AP:
+        translated_regs[-INTERRUPT_CFG] = LPS331AP_INTERRUPT_CFG;
+        translated_regs[-INT_SOURCE]    = LPS331AP_INT_SOURCE;
+        translated_regs[-THS_P_L]       = LPS331AP_THS_P_L;
+        translated_regs[-THS_P_H]       = LPS331AP_THS_P_H;
+        return true;
+        break;
+    }
+}
+
+// turns on sensor and enables continuous output
+void LPS::enableDefault(void)
+{
+    if (_device == device_25H)
+    {
+        // 0xB0 = 0b10110000
+        // PD = 1 (active mode);  ODR = 011 (12.5 Hz pressure & temperature output data rate)
+        writeReg(CTRL_REG1, 0xB0);
+    }
+    else if (_device == device_331AP)
+    {
+        // 0xE0 = 0b11100000
+        // PD = 1 (active mode);  ODR = 110 (12.5 Hz pressure & temperature output data rate)
+        writeReg(CTRL_REG1, 0xE0);
+    }
+}
+
+// writes register
+void LPS::writeReg(char reg, char value)
+{
+    // if dummy register address, look up actual translated address (based on device type)
+    if (reg < 0)
+    {
+        reg = translated_regs[-reg];
+    }
+    char command[] = {reg,value};
+    _i2c.write(address << 1,command,2);
+}
+
+// reads register
+int8_t LPS::readReg(char reg)
+{
+    char value;
+    // if dummy register address, look up actual translated address (based on device type)
+    if(reg < 0)
+    {
+        reg = translated_regs[-reg];
+    }
+    _i2c.write(address << 1,&reg,1);
+    _i2c.read((address << 1)|1,&value,1);
+  
+    return value;
+}
+
+// reads pressure in millibars (mbar)/hectopascals (hPa)
+float LPS::readPressureMillibars(void)
+{
+    return (float)readPressureRaw() / 4096;
+}
+
+// reads pressure in inches of mercury (inHg)
+float LPS::readPressureInchesHg(void)
+{
+    return (float)readPressureRaw() / 138706.5;
+}
+
+// reads pressure and returns raw 24-bit sensor output
+int32_t LPS::readPressureRaw(void)
+{
+    // assert MSB to enable register address auto-increment
+  
+    char command = PRESS_OUT_XL | (1 << 7);
+    char p[3];
+    _i2c.write(address << 1,&command,1);
+    _i2c.read((address << 1)| 1,p,3);
+  
+    // combine int8_ts
+    return (int32_t)(int8_t)p[2] << 16 | (uint16_t)p[1] << 8 | p[0];
+}
+
+// reads temperature in degrees C
+float LPS::readTemperatureC(void)
+{
+    return 42.5 + (float)readTemperatureRaw() / 480;
+}
+
+// reads temperature in degrees F
+float LPS::readTemperatureF(void)
+{
+    return 108.5 + (float)readTemperatureRaw() / 480 * 1.8;
+}
+
+// reads temperature and returns raw 16-bit sensor output
+int16_t LPS::readTemperatureRaw(void)
+{
+    char command = TEMP_OUT_L | (1 << 7);
+  
+    // assert MSB to enable register address auto-increment
+    char t[2];
+    _i2c.write(address << 1,&command,1);
+    _i2c.read((address << 1)| 1,t,2);
+
+    // combine bytes
+    return (int16_t)(t[1] << 8 | t[0]);
+}
+
+// converts pressure in mbar to altitude in meters, using 1976 US
+// Standard Atmosphere model (note that this formula only applies to a
+// height of 11 km, or about 36000 ft)
+//  If altimeter setting (QNH, barometric pressure adjusted to sea
+//  level) is given, this function returns an indicated altitude
+//  compensated for actual regional pressure; otherwise, it returns
+//  the pressure altitude above the standard pressure level of 1013.25
+//  mbar or 29.9213 inHg
+float LPS::pressureToAltitudeMeters(double pressure_mbar, double altimeter_setting_mbar)
+{
+    return (1 - pow(pressure_mbar / altimeter_setting_mbar, 0.190263)) * 44330.8;//pressure;
+}
+
+// converts pressure in inHg to altitude in feet; see notes above
+float LPS::pressureToAltitudeFeet(double pressure_inHg, double altimeter_setting_inHg)
+{
+    return (1 - pow(pressure_inHg / altimeter_setting_inHg, 0.190263)) * 145442;//pressure;
+}
+
+// Private Methods ///////////////////////////////////////////////////
+
+bool LPS::detectDeviceAndAddress(deviceType device, sa0State sa0)
+{
+    if (sa0 == sa0_auto || sa0 == sa0_high)
+    {
+        address = SA0_HIGH_ADDRESS;
+        if (detectDevice(device)) return true;
+    }
+    if (sa0 == sa0_auto || sa0 == sa0_low)
+    {
+        address = SA0_LOW_ADDRESS;
+        if (detectDevice(device)) return true;
+    }
+
+    return false;
+}
+
+bool LPS::detectDevice(deviceType device)
+{
+    uint8_t id = testWhoAmI(address);
+  
+    if ((device == device_auto || device == device_25H) && id == (uint8_t)LPS25H_WHO_ID)
+    {
+        _device = device_25H;
+        return true;
+    }
+    if ((device == device_auto || device == device_331AP) && id == (uint8_t)LPS331AP_WHO_ID)
+    {
+        _device = device_331AP;
+        return true;
+    }
+
+    return false;
+}
+
+int LPS::testWhoAmI(uint8_t address)
+{
+    char command = WHO_AM_I;
+    char status = 0;
+    _i2c.write(address << 1,&command,1);
+    _i2c.read((address << 1)| 1,&status,1);
+    return status;
+}
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