Revision 0:f8ee2a5e377a, committed 2012-04-17

Comitter:

mk

Date:

Tue Apr 17 07:44:48 2012 +0000

Child:

1:b2adf1b62898

Commit message:

Changed in this revision

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/MPL115A1.cpp	Tue Apr 17 07:44:48 2012 +0000
@@ -0,0 +1,221 @@
+/* mbed MPL115A1 (Barometric Pressure Sensor) Library
+ *
+ * This code is based on application notes and
+ * Sparkfun example code, written by Jim Lindblom <jim at sparkfun.com>
+ *
+ * Copyright (c) 2012 Mitja Kleider
+ *
+ * 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.
+ */
+
+// TODO: support shutdown pin
+
+
+#include "MPL115A1.h"
+
+MPL115A1::MPL115A1(SPI& spi, PinName ncs) : _spi(spi), _cs(ncs)
+{
+    _cs = 1;
+    // sdn = 1; // sensor on
+    
+    // SCL idle low, sample data on rising edge
+    _spi.format(8, 0); // 8bit, POL 0, PHA 0
+    _spi.frequency(1000000); // 1MHz
+}
+
+void MPL115A1::write_register(uint8_t address, char data)
+{
+    //write any data byte to any single address
+    //adds a 0 to the MSB of the address byte (WRITE mode)
+
+    address &= 0x7F;
+
+    _cs = 0;
+    wait_ms(1);
+    _spi.write(address);
+    wait_ms(1);
+    _spi.write(data);
+    wait_ms(1);
+    _cs = 1;
+}
+
+char MPL115A1::read_register(uint8_t address)
+{
+    // returns the contents of any 1 byte register from any address
+    // sets the MSB for every address byte (READ mode)
+
+    char byte;
+
+    address |= 0x80;
+
+    _cs = 0;
+    _spi.write(address);
+    byte = _spi.write(0x00);
+    _cs = 1;
+
+    return byte;
+}
+
+float MPL115A1::readPressure()
+{
+    // read pressure, temperature and coefficients, calculate and return absolute pressure [kPa]
+
+    write_register(MPL115A1_STARTBOTH, 0x00); // start temperature and pressure conversions
+    wait_ms(10); // AN: data is typically ready after 3ms, DS for both: max. 1ms
+    
+    // read raw pressure
+    uiPH = read_register(MPL115A1_PRESH);
+    uiPL = read_register(MPL115A1_PRESL);
+    uiTH = read_register(MPL115A1_TEMPH);
+    uiTL = read_register(MPL115A1_TEMPL);
+    
+    uiPadc = (unsigned int) uiPH << 8;
+    uiPadc += (unsigned int) uiPL & 0x00FF;
+    uiTadc = (unsigned int) uiTH << 8;
+    uiTadc += (unsigned int) uiTL & 0x00FF;
+    
+    // read coefficients, put into 16-bit Variables
+    // a0, pressure offset coefficient
+    sia0MSB = read_register(MPL115A1_A0MSB);
+    sia0LSB = read_register(MPL115A1_A0LSB);
+    sia0 = (signed int) sia0MSB << 8;
+    sia0 += (signed int) sia0LSB & 0x00FF;
+    
+    // b1, pressure sensitivity coefficient
+    sib1MSB = read_register(MPL115A1_B1MSB);
+    sib1LSB = read_register(MPL115A1_B1LSB);
+    sib1 = (signed int) sib1MSB << 8;
+    sib1 += (signed int) sib1LSB & 0x00FF;
+    
+    // b2, 1st order temperature offset coefficient (TCO)
+    sib2MSB = read_register(MPL115A1_B2MSB);
+    sib2LSB = read_register(MPL115A1_B2LSB);
+    sib2 = (signed int) sib2MSB << 8;
+    sib2 += (signed int) sib2LSB & 0x00FF;
+    
+    // c12, temperature sensitivity coefficient (TCS)
+    sic12MSB = read_register(MPL115A1_C12MSB);
+    sic12LSB = read_register(MPL115A1_C12LSB);
+    sic12 = (signed int) sic12MSB << 8;
+    sic12 += (signed int) sic12LSB & 0x00FF;
+    
+    // c11, pressure linearity (2nd order) coefficient
+    sic11MSB = read_register(MPL115A1_C11MSB);
+    sic11LSB = read_register(MPL115A1_C11LSB);
+    sic11 = (signed int) sic11MSB << 8;
+    sic11 += (signed int) sic11LSB & 0x00FF;
+    
+    // c22, 2nd order temperature offset coefficient
+    sic22MSB = read_register(MPL115A1_C22MSB);
+    sic22LSB = read_register(MPL115A1_C22LSB);
+    sic22 = (signed int) sic22MSB << 8;
+    sic22 += (signed int) sic22LSB & 0x00FF;
+    
+    // Coefficient 9 equation compensation
+    
+    // 10bit stored in 16bit, shift right
+    uiPadc = uiPadc >> 6;
+    uiTadc = uiTadc >> 6;
+    
+    // Step 1: c11x1 = c11 * Padc
+    lt1 = (signed long) sic11;
+    lt2 = (signed long) uiPadc;
+    lt3 = lt1*lt2;
+    si_c11x1 = (signed long) lt3;
+    
+    // Step 2: a11 = b1 + c11x1
+    lt1 = ((signed long)sib1)<<14;
+    lt2 = (signed long) si_c11x1;
+    lt3 = lt1 + lt2;
+    si_a11 = (signed long)(lt3>>14);
+    
+    // Step 3: c12x2 = c12 * Tadc
+    lt1 = (signed long) sic12;
+    lt2 = (signed long) uiTadc;
+    lt3 = lt1*lt2;
+    si_c12x2 = (signed long)lt3;
+    
+    // Step 4: a1 = a11 + c12x2
+    lt1 = ((signed long)si_a11<<11);
+    lt2 = (signed long)si_c12x2;
+    lt3 = lt1 + lt2;
+    si_a1 = (signed long) lt3>>11;
+    
+    // Step 5: c22x2 = c22*Tadc
+    lt1 = (signed long)sic22;
+    lt2 = (signed long)uiTadc;
+    lt3 = lt1 * lt2;
+    si_c22x2 = (signed long)(lt3);
+    
+    // Step 6: a2 = b2 + c22x2
+    lt1 = ((signed long)sib2<<15);
+    lt2 = ((signed long)si_c22x2>1);
+    lt3 = lt1+lt2;
+    si_a2 = ((signed long)lt3>>16);
+    
+    // Step 7: a1x1 = a1 * Padc
+    lt1 = (signed long)si_a1;
+    lt2 = (signed long)uiPadc;
+    lt3 = lt1*lt2;
+    si_a1x1 = (signed long)(lt3);
+    
+    // Step 8: y1 = a0 + a1x1
+    lt1 = ((signed long)sia0<<10);
+    lt2 = (signed long)si_a1x1;
+    lt3 = lt1+lt2;
+    si_y1 = ((signed long)lt3>>10);
+    
+    // Step 9: a2x2 = a2 * Tadc
+    lt1 = (signed long)si_a2;
+    lt2 = (signed long)uiTadc;
+    lt3 = lt1*lt2;
+    si_a2x2 = (signed long)(lt3);
+    
+    // Step 10: pComp = y1 + a2x2
+    lt1 = ((signed long)si_y1<<10);
+    lt2 = (signed long)si_a2x2;
+    lt3 = lt1+lt2;
+    
+    // Fixed point result with rounding
+    //siPcomp = ((signed int)lt3>>13);
+    siPcomp = lt3/8192;
+    
+    // decPcomp is defined as a floating point number
+    // Conversion to decimal value from 1023 ADC count value
+    // ADC counts are 0 to 1023, pressure is 50 to 115kPa respectively
+    decPcomp = ((65.0/1023.0)*siPcomp)+50;
+    
+    return decPcomp;
+}
+
+float MPL115A1::readTemperature()
+{
+    // read, calculate and return temperature
+
+    write_register(MPL115A1_STARTTEMP, 0x00); // start temperature conversion
+    wait_ms(10); // AN: data is typically ready after 3ms, DS for temp: max. 0.7ms
+    
+    // read raw temperature
+    uiTH = read_register(MPL115A1_TEMPH);
+    uiTL = read_register(MPL115A1_TEMPL);
+    
+    uiTadc = (unsigned int) uiTH << 8;
+    uiTadc += (unsigned int) uiTL & 0x00FF;
+    
+    // 10bit stored in 16bit, shift right
+    uiTadc = uiTadc >> 6;
+    
+    // Tadc is 472 counts at 25degC, -5.35 counts/degC
+    // return ((float)uiTadc - 472.0)/(-5.35) + 25
+    return (605.75-uiTadc)/5.35;
+}
\ No newline at end of file

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/MPL115A1.h	Tue Apr 17 07:44:48 2012 +0000
@@ -0,0 +1,80 @@
+#ifndef MPL115A1_H
+#define MPL115A1_H
+
+#include "mbed.h"
+
+/**  barometric pressure and temperature sensor MPL115A1 control class, based on SPI
+ *
+ * Example:
+ * @code
+ * #include "mbed.h"
+ * #include "MPL115A1.h"
+ * 
+ * SPI spi(p11,p12,p13);
+ * MPL115A1 bar(spi, p14);
+ * 
+ * Serial pc(USBTX, USBRX);
+ * 
+ * int main() {
+ *     while(1) {
+ *         wait(10);
+ *         pc.printf("Pressure is %f\n", bar.readPressure());
+ *         pc.printf("Temperature is %f\n", bar.readTemperature());
+ *     }
+ * }
+ * @endcode
+ */
+
+                         // real addresses, in read_register: address |= 0x80
+#define MPL115A1_PRESH    0x00    // 80
+#define MPL115A1_PRESL    0x02    // 82
+#define MPL115A1_TEMPH    0x04    // 84
+#define MPL115A1_TEMPL    0x06    // 86
+
+#define MPL115A1_A0MSB    0x08    // 88
+#define MPL115A1_A0LSB    0x0A    // 8A
+#define MPL115A1_B1MSB    0x0C    // 8C
+#define MPL115A1_B1LSB    0x0E    // 8E
+#define MPL115A1_B2MSB    0x10    // 90
+#define MPL115A1_B2LSB    0x12    // 92
+#define MPL115A1_C12MSB   0x14    // 94
+#define MPL115A1_C12LSB   0x16    // 96
+#define MPL115A1_C11MSB   0x18    // 98
+#define MPL115A1_C11LSB   0x1A    // 9A
+#define MPL115A1_C22MSB   0x1C    // 9C
+#define MPL115A1_C22LSB   0x1E    // 9E
+
+#define MPL115A1_STARTPRES 0x20 // start pressure measurement
+#define MPL115A1_STARTTEMP 0x22 // start temperature measurement
+#define MPL115A1_STARTBOTH 0x24 // start both simultaneously
+
+class MPL115A1 {
+private:
+    SPI& _spi;
+    DigitalOut _cs; // chip select, active low
+    //DigitalOut sdn; // shutdown pin, high=on, low=off
+    
+public:
+    MPL115A1(SPI& spi, PinName ncs);
+    float readPressure();
+    float readTemperature();
+
+private:
+    void write_register(uint8_t address, char data);
+    char read_register(uint8_t address);
+
+    signed char sia0MSB, sia0LSB;
+    signed char sib1MSB, sib1LSB;
+    signed char sib2MSB, sib2LSB;
+    signed char sic12MSB, sic12LSB;
+    signed char sic11MSB, sic11LSB;
+    signed char sic22MSB, sic22LSB;
+    signed int sia0, sib1, sib2, sic12, sic11, sic22, siPcomp;
+    float decPcomp;
+    signed long lt1, lt2, lt3, si_c11x1, si_a11, si_c12x2;
+    signed long si_a1, si_c22x2, si_a2, si_a1x1, si_y1, si_a2x2;
+    unsigned int uiPadc, uiTadc;
+    unsigned char uiPH, uiPL, uiTH, uiTL;
+};
+
+#endif
\ No newline at end of file