mbed MPL115A1 (Barometric Pressure Sensor) Library
Dependents: MPL115A1_HelloWorld
MPL115A1.cpp
- Committer:
- mk
- Date:
- 2012-04-17
- Revision:
- 0:f8ee2a5e377a
- Child:
- 1:b2adf1b62898
File content as of revision 0:f8ee2a5e377a:
/* 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; }