MPL115A1 - mbed MPL115A1 (Barometric Pressure Sensor) Library

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mbed MPL115A1 (Barometric Pressure Sensor) Library

MPL115A1.cpp@1:b2adf1b62898, 2012-04-17 (annotated)

Committer:: mk
Date:: Tue Apr 17 15:35:24 2012 +0000
Revision:: 1:b2adf1b62898
Parent:: 0:f8ee2a5e377a

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User	Revision	Line number	New contents of line
mk	0:f8ee2a5e377a	1	/* mbed MPL115A1 (Barometric Pressure Sensor) Library
mk	0:f8ee2a5e377a	2	*
mk	0:f8ee2a5e377a	3	* This code is based on application notes and
mk	0:f8ee2a5e377a	4	* Sparkfun example code, written by Jim Lindblom <jim at sparkfun.com>
mk	0:f8ee2a5e377a	5	*
mk	0:f8ee2a5e377a	6	* Copyright (c) 2012 Mitja Kleider
mk	0:f8ee2a5e377a	7	*
mk	0:f8ee2a5e377a	8	* Licensed under the Apache License, Version 2.0 (the "License");
mk	0:f8ee2a5e377a	9	* you may not use this file except in compliance with the License.
mk	0:f8ee2a5e377a	10	* You may obtain a copy of the License at
mk	0:f8ee2a5e377a	11	*
mk	0:f8ee2a5e377a	12	* http://www.apache.org/licenses/LICENSE-2.0
mk	0:f8ee2a5e377a	13	*
mk	0:f8ee2a5e377a	14	* Unless required by applicable law or agreed to in writing, software
mk	0:f8ee2a5e377a	15	* distributed under the License is distributed on an "AS IS" BASIS,
mk	0:f8ee2a5e377a	16	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
mk	0:f8ee2a5e377a	17	* See the License for the specific language governing permissions and
mk	0:f8ee2a5e377a	18	* limitations under the License.
mk	0:f8ee2a5e377a	19	*/
mk	0:f8ee2a5e377a	20
mk	0:f8ee2a5e377a	21	// TODO: support shutdown pin
mk	0:f8ee2a5e377a	22
mk	0:f8ee2a5e377a	23
mk	0:f8ee2a5e377a	24	#include "MPL115A1.h"
mk	0:f8ee2a5e377a	25
mk	0:f8ee2a5e377a	26	MPL115A1::MPL115A1(SPI& spi, PinName ncs) : _spi(spi), _cs(ncs)
mk	0:f8ee2a5e377a	27	{
mk	0:f8ee2a5e377a	28	_cs = 1;
mk	0:f8ee2a5e377a	29	// sdn = 1; // sensor on
mk	0:f8ee2a5e377a	30
mk	0:f8ee2a5e377a	31	// SCL idle low, sample data on rising edge
mk	0:f8ee2a5e377a	32	_spi.format(8, 0); // 8bit, POL 0, PHA 0
mk	0:f8ee2a5e377a	33	_spi.frequency(1000000); // 1MHz
mk	0:f8ee2a5e377a	34	}
mk	0:f8ee2a5e377a	35
mk	0:f8ee2a5e377a	36	void MPL115A1::write_register(uint8_t address, char data)
mk	0:f8ee2a5e377a	37	{
mk	0:f8ee2a5e377a	38	//write any data byte to any single address
mk	0:f8ee2a5e377a	39	//adds a 0 to the MSB of the address byte (WRITE mode)
mk	0:f8ee2a5e377a	40
mk	0:f8ee2a5e377a	41	address &= 0x7F;
mk	0:f8ee2a5e377a	42
mk	0:f8ee2a5e377a	43	_cs = 0;
mk	0:f8ee2a5e377a	44	wait_ms(1);
mk	0:f8ee2a5e377a	45	_spi.write(address);
mk	0:f8ee2a5e377a	46	wait_ms(1);
mk	0:f8ee2a5e377a	47	_spi.write(data);
mk	0:f8ee2a5e377a	48	wait_ms(1);
mk	0:f8ee2a5e377a	49	_cs = 1;
mk	0:f8ee2a5e377a	50	}
mk	0:f8ee2a5e377a	51
mk	0:f8ee2a5e377a	52	char MPL115A1::read_register(uint8_t address)
mk	0:f8ee2a5e377a	53	{
mk	0:f8ee2a5e377a	54	// returns the contents of any 1 byte register from any address
mk	0:f8ee2a5e377a	55	// sets the MSB for every address byte (READ mode)
mk	0:f8ee2a5e377a	56
mk	0:f8ee2a5e377a	57	char byte;
mk	0:f8ee2a5e377a	58
mk	0:f8ee2a5e377a	59	address \|= 0x80;
mk	0:f8ee2a5e377a	60
mk	0:f8ee2a5e377a	61	_cs = 0;
mk	0:f8ee2a5e377a	62	_spi.write(address);
mk	0:f8ee2a5e377a	63	byte = _spi.write(0x00);
mk	0:f8ee2a5e377a	64	_cs = 1;
mk	0:f8ee2a5e377a	65
mk	0:f8ee2a5e377a	66	return byte;
mk	0:f8ee2a5e377a	67	}
mk	0:f8ee2a5e377a	68
mk	0:f8ee2a5e377a	69	float MPL115A1::readPressure()
mk	0:f8ee2a5e377a	70	{
mk	0:f8ee2a5e377a	71	// read pressure, temperature and coefficients, calculate and return absolute pressure [kPa]
mk	0:f8ee2a5e377a	72
mk	0:f8ee2a5e377a	73	write_register(MPL115A1_STARTBOTH, 0x00); // start temperature and pressure conversions
mk	0:f8ee2a5e377a	74	wait_ms(10); // AN: data is typically ready after 3ms, DS for both: max. 1ms
mk	0:f8ee2a5e377a	75
mk	0:f8ee2a5e377a	76	// read raw pressure
mk	0:f8ee2a5e377a	77	uiPH = read_register(MPL115A1_PRESH);
mk	0:f8ee2a5e377a	78	uiPL = read_register(MPL115A1_PRESL);
mk	0:f8ee2a5e377a	79	uiTH = read_register(MPL115A1_TEMPH);
mk	0:f8ee2a5e377a	80	uiTL = read_register(MPL115A1_TEMPL);
mk	0:f8ee2a5e377a	81
mk	0:f8ee2a5e377a	82	uiPadc = (unsigned int) uiPH << 8;
mk	0:f8ee2a5e377a	83	uiPadc += (unsigned int) uiPL & 0x00FF;
mk	0:f8ee2a5e377a	84	uiTadc = (unsigned int) uiTH << 8;
mk	0:f8ee2a5e377a	85	uiTadc += (unsigned int) uiTL & 0x00FF;
mk	0:f8ee2a5e377a	86
mk	0:f8ee2a5e377a	87	// read coefficients, put into 16-bit Variables
mk	0:f8ee2a5e377a	88	// a0, pressure offset coefficient
mk	0:f8ee2a5e377a	89	sia0MSB = read_register(MPL115A1_A0MSB);
mk	0:f8ee2a5e377a	90	sia0LSB = read_register(MPL115A1_A0LSB);
mk	0:f8ee2a5e377a	91	sia0 = (signed int) sia0MSB << 8;
mk	0:f8ee2a5e377a	92	sia0 += (signed int) sia0LSB & 0x00FF;
mk	0:f8ee2a5e377a	93
mk	0:f8ee2a5e377a	94	// b1, pressure sensitivity coefficient
mk	0:f8ee2a5e377a	95	sib1MSB = read_register(MPL115A1_B1MSB);
mk	0:f8ee2a5e377a	96	sib1LSB = read_register(MPL115A1_B1LSB);
mk	0:f8ee2a5e377a	97	sib1 = (signed int) sib1MSB << 8;
mk	0:f8ee2a5e377a	98	sib1 += (signed int) sib1LSB & 0x00FF;
mk	0:f8ee2a5e377a	99
mk	0:f8ee2a5e377a	100	// b2, 1st order temperature offset coefficient (TCO)
mk	0:f8ee2a5e377a	101	sib2MSB = read_register(MPL115A1_B2MSB);
mk	0:f8ee2a5e377a	102	sib2LSB = read_register(MPL115A1_B2LSB);
mk	0:f8ee2a5e377a	103	sib2 = (signed int) sib2MSB << 8;
mk	0:f8ee2a5e377a	104	sib2 += (signed int) sib2LSB & 0x00FF;
mk	0:f8ee2a5e377a	105
mk	0:f8ee2a5e377a	106	// c12, temperature sensitivity coefficient (TCS)
mk	0:f8ee2a5e377a	107	sic12MSB = read_register(MPL115A1_C12MSB);
mk	0:f8ee2a5e377a	108	sic12LSB = read_register(MPL115A1_C12LSB);
mk	0:f8ee2a5e377a	109	sic12 = (signed int) sic12MSB << 8;
mk	0:f8ee2a5e377a	110	sic12 += (signed int) sic12LSB & 0x00FF;
mk	0:f8ee2a5e377a	111
mk	0:f8ee2a5e377a	112	// c11, pressure linearity (2nd order) coefficient
mk	0:f8ee2a5e377a	113	sic11MSB = read_register(MPL115A1_C11MSB);
mk	0:f8ee2a5e377a	114	sic11LSB = read_register(MPL115A1_C11LSB);
mk	0:f8ee2a5e377a	115	sic11 = (signed int) sic11MSB << 8;
mk	0:f8ee2a5e377a	116	sic11 += (signed int) sic11LSB & 0x00FF;
mk	0:f8ee2a5e377a	117
mk	0:f8ee2a5e377a	118	// c22, 2nd order temperature offset coefficient
mk	0:f8ee2a5e377a	119	sic22MSB = read_register(MPL115A1_C22MSB);
mk	0:f8ee2a5e377a	120	sic22LSB = read_register(MPL115A1_C22LSB);
mk	0:f8ee2a5e377a	121	sic22 = (signed int) sic22MSB << 8;
mk	0:f8ee2a5e377a	122	sic22 += (signed int) sic22LSB & 0x00FF;
mk	0:f8ee2a5e377a	123
mk	0:f8ee2a5e377a	124	// Coefficient 9 equation compensation
mk	0:f8ee2a5e377a	125
mk	0:f8ee2a5e377a	126	// 10bit stored in 16bit, shift right
mk	0:f8ee2a5e377a	127	uiPadc = uiPadc >> 6;
mk	0:f8ee2a5e377a	128	uiTadc = uiTadc >> 6;
mk	0:f8ee2a5e377a	129
mk	0:f8ee2a5e377a	130	// Step 1: c11x1 = c11 * Padc
mk	0:f8ee2a5e377a	131	lt1 = (signed long) sic11;
mk	0:f8ee2a5e377a	132	lt2 = (signed long) uiPadc;
mk	0:f8ee2a5e377a	133	lt3 = lt1*lt2;
mk	0:f8ee2a5e377a	134	si_c11x1 = (signed long) lt3;
mk	0:f8ee2a5e377a	135
mk	0:f8ee2a5e377a	136	// Step 2: a11 = b1 + c11x1
mk	0:f8ee2a5e377a	137	lt1 = ((signed long)sib1)<<14;
mk	0:f8ee2a5e377a	138	lt2 = (signed long) si_c11x1;
mk	0:f8ee2a5e377a	139	lt3 = lt1 + lt2;
mk	0:f8ee2a5e377a	140	si_a11 = (signed long)(lt3>>14);
mk	0:f8ee2a5e377a	141
mk	0:f8ee2a5e377a	142	// Step 3: c12x2 = c12 * Tadc
mk	0:f8ee2a5e377a	143	lt1 = (signed long) sic12;
mk	0:f8ee2a5e377a	144	lt2 = (signed long) uiTadc;
mk	0:f8ee2a5e377a	145	lt3 = lt1*lt2;
mk	0:f8ee2a5e377a	146	si_c12x2 = (signed long)lt3;
mk	0:f8ee2a5e377a	147
mk	0:f8ee2a5e377a	148	// Step 4: a1 = a11 + c12x2
mk	0:f8ee2a5e377a	149	lt1 = ((signed long)si_a11<<11);
mk	0:f8ee2a5e377a	150	lt2 = (signed long)si_c12x2;
mk	0:f8ee2a5e377a	151	lt3 = lt1 + lt2;
mk	0:f8ee2a5e377a	152	si_a1 = (signed long) lt3>>11;
mk	0:f8ee2a5e377a	153
mk	0:f8ee2a5e377a	154	// Step 5: c22x2 = c22*Tadc
mk	0:f8ee2a5e377a	155	lt1 = (signed long)sic22;
mk	0:f8ee2a5e377a	156	lt2 = (signed long)uiTadc;
mk	0:f8ee2a5e377a	157	lt3 = lt1 * lt2;
mk	0:f8ee2a5e377a	158	si_c22x2 = (signed long)(lt3);
mk	0:f8ee2a5e377a	159
mk	0:f8ee2a5e377a	160	// Step 6: a2 = b2 + c22x2
mk	0:f8ee2a5e377a	161	lt1 = ((signed long)sib2<<15);
mk	0:f8ee2a5e377a	162	lt2 = ((signed long)si_c22x2>1);
mk	0:f8ee2a5e377a	163	lt3 = lt1+lt2;
mk	0:f8ee2a5e377a	164	si_a2 = ((signed long)lt3>>16);
mk	0:f8ee2a5e377a	165
mk	0:f8ee2a5e377a	166	// Step 7: a1x1 = a1 * Padc
mk	0:f8ee2a5e377a	167	lt1 = (signed long)si_a1;
mk	0:f8ee2a5e377a	168	lt2 = (signed long)uiPadc;
mk	0:f8ee2a5e377a	169	lt3 = lt1*lt2;
mk	0:f8ee2a5e377a	170	si_a1x1 = (signed long)(lt3);
mk	0:f8ee2a5e377a	171
mk	0:f8ee2a5e377a	172	// Step 8: y1 = a0 + a1x1
mk	0:f8ee2a5e377a	173	lt1 = ((signed long)sia0<<10);
mk	0:f8ee2a5e377a	174	lt2 = (signed long)si_a1x1;
mk	0:f8ee2a5e377a	175	lt3 = lt1+lt2;
mk	0:f8ee2a5e377a	176	si_y1 = ((signed long)lt3>>10);
mk	0:f8ee2a5e377a	177
mk	0:f8ee2a5e377a	178	// Step 9: a2x2 = a2 * Tadc
mk	0:f8ee2a5e377a	179	lt1 = (signed long)si_a2;
mk	0:f8ee2a5e377a	180	lt2 = (signed long)uiTadc;
mk	0:f8ee2a5e377a	181	lt3 = lt1*lt2;
mk	0:f8ee2a5e377a	182	si_a2x2 = (signed long)(lt3);
mk	0:f8ee2a5e377a	183
mk	0:f8ee2a5e377a	184	// Step 10: pComp = y1 + a2x2
mk	0:f8ee2a5e377a	185	lt1 = ((signed long)si_y1<<10);
mk	0:f8ee2a5e377a	186	lt2 = (signed long)si_a2x2;
mk	0:f8ee2a5e377a	187	lt3 = lt1+lt2;
mk	0:f8ee2a5e377a	188
mk	0:f8ee2a5e377a	189	// Fixed point result with rounding
mk	0:f8ee2a5e377a	190	//siPcomp = ((signed int)lt3>>13);
mk	0:f8ee2a5e377a	191	siPcomp = lt3/8192;
mk	0:f8ee2a5e377a	192
mk	0:f8ee2a5e377a	193	// decPcomp is defined as a floating point number
mk	0:f8ee2a5e377a	194	// Conversion to decimal value from 1023 ADC count value
mk	0:f8ee2a5e377a	195	// ADC counts are 0 to 1023, pressure is 50 to 115kPa respectively
mk	0:f8ee2a5e377a	196	decPcomp = ((65.0/1023.0)*siPcomp)+50;
mk	0:f8ee2a5e377a	197
mk	0:f8ee2a5e377a	198	return decPcomp;
mk	0:f8ee2a5e377a	199	}
mk	0:f8ee2a5e377a	200
mk	0:f8ee2a5e377a	201	float MPL115A1::readTemperature()
mk	0:f8ee2a5e377a	202	{
mk	0:f8ee2a5e377a	203	// read, calculate and return temperature
mk	0:f8ee2a5e377a	204
mk	0:f8ee2a5e377a	205	write_register(MPL115A1_STARTTEMP, 0x00); // start temperature conversion
mk	0:f8ee2a5e377a	206	wait_ms(10); // AN: data is typically ready after 3ms, DS for temp: max. 0.7ms
mk	0:f8ee2a5e377a	207
mk	0:f8ee2a5e377a	208	// read raw temperature
mk	0:f8ee2a5e377a	209	uiTH = read_register(MPL115A1_TEMPH);
mk	0:f8ee2a5e377a	210	uiTL = read_register(MPL115A1_TEMPL);
mk	0:f8ee2a5e377a	211
mk	0:f8ee2a5e377a	212	uiTadc = (unsigned int) uiTH << 8;
mk	0:f8ee2a5e377a	213	uiTadc += (unsigned int) uiTL & 0x00FF;
mk	0:f8ee2a5e377a	214
mk	0:f8ee2a5e377a	215	// 10bit stored in 16bit, shift right
mk	0:f8ee2a5e377a	216	uiTadc = uiTadc >> 6;
mk	0:f8ee2a5e377a	217
mk	0:f8ee2a5e377a	218	// Tadc is 472 counts at 25degC, -5.35 counts/degC
mk	0:f8ee2a5e377a	219	// return ((float)uiTadc - 472.0)/(-5.35) + 25
mk	1:b2adf1b62898	220	return (605.75-uiTadc)*0.186916;
mk	0:f8ee2a5e377a	221	}

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Type:	Library
Created:	17 Apr 2012
Imports:	186
Forks:	0
Commits:	2
Dependents:	1
Dependencies:	0
Followers:	6

MPL115A1.cpp@1:b2adf1b62898, 2012-04-17 (annotated)

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