{"id":10,"date":"2010-07-26T09:04:55","date_gmt":"2010-07-26T09:04:55","guid":{"rendered":"http:\/\/ulrichard.is-a-geek.net\/?p=10"},"modified":"2010-07-26T09:04:55","modified_gmt":"2010-07-26T09:04:55","slug":"arduino-code-for-the-intersema-pressure-sensor","status":"publish","type":"post","link":"https:\/\/ulrichard.ch\/blog\/?p=10","title":{"rendered":"Arduino Code for the MS5534C Intersema pressure sensor"},"content":{"rendered":"

After receiving personal messages on the arduino forum asking for the code for the Intersema pressure sensor, I paste my code here. It is based on the code from Hari Nair for the open source solar vario<\/a> that I bought from him.<\/p>\n

<\/p>\n

I use it in my ChopperControl<\/a> project which is not quite ready for releasing right now. It’s about controlling an RC helicopter from the openmoko freerunner smartphone over a bluetooth link.<\/p>\n

I ported the code to the Arduino. Later, I learned about SPI, and asked Hari, if it was possible to interface it with SPI. He told me that it’s not really thought that way, but possible. He sent me a note from Intersema describing that.<\/p>\n

In the meantime, Intersema released a sensor with I2C interface which I’m going to order some soon.<\/p>\n

Uploading the packed file didn’t work at the moment, so I pasted them below. I will upload the files as soon as I figure out how…<\/p>\n

<\/p>\n

*******************\u00c2\u00a0\u00c2\u00a0 IntersemaBaro.h :\u00c2\u00a0 **********************<\/p>\n

\/*
\n* Interface to Intersema Barometric pressure sensor.
\n* For the moment, only the MS5534C is supported.
\n* Others might be added in the future, especially the one with I2C.
\n*
\n* Created 14 Jan 2010
\n* By Richard Ulrich
\n* Inspired by the work of Hari Nair
\n*\/
\n#ifndef INTERSEMA_BARO_H
\n#define INTERSEMA_BARO_H<\/p>\n

#include <WProgram.h><\/p>\n

class\u00c2\u00a0 BaroPressure_MS5534C
\n{
\npublic:
\nBaroPressure_MS5534C(uint8_t pinMCLK, uint8_t pinSCLK, uint8_t pinDIN, uint8_t pinDOUT);<\/p>\n

void begin();<\/p>\n

long getHeightCentiMeters(void)
\n{
\nreturn AcquireAveragedSampleCm(NUM_SAMP_FOR_AVG);
\n}<\/p>\n

long getHeightMeters(void)
\n{
\nlong AltCm = getHeightCentiMeters();
\nlong AltAvgM\u00c2\u00a0 = (AltCm >= 0 ? (AltCm + 50L) \/ 100L : (AltCm – 50L) \/ 100L);
\nreturn AltAvgM;
\n}<\/p>\n

private:
\nvoid ResetSensor();
\nvoid ReadCoefficients(void);
\nsize_t ReadCoefficient(unsigned char addr);
\nvoid SendCommand(unsigned long cmd, size_t nbits);
\nunsigned int ReadWord(void);
\nlong AcquireAveragedSampleCm(const size_t nSamples);
\nlong ConvertPressureTemperature(unsigned int pressure, unsigned int temperature);
\nvoid TriggerTemperatureSample(void);
\nvoid TriggerPressureSample(void);
\nlong PascalToCentimeter(long pressurePa);<\/p>\n

enum SensorStates
\n{
\nSENSOR_READ_TEMPERATURE
\n};<\/p>\n

static const size_t NUM_SAMP_FOR_AVG = 4;<\/p>\n

const uint8_t pinMCLK_; \/\/ master clock 32.5 kHz
\nconst uint8_t pinSCLK_; \/\/ serial clock
\nconst uint8_t pinDIN_;\u00c2\u00a0 \/\/ data in\u00c2\u00a0 (out on the arduino)
\nconst uint8_t pinDOUT_; \/\/ data out (in\u00c2\u00a0 on the arduino)<\/p>\n

unsigned int coefficients_[6];
\nSensorStates SensorState_;
\nsize_t\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0 SmpCnt_;
\n};<\/p>\n

#endif<\/p>\n

*******************\u00c2\u00a0\u00c2\u00a0 IntersemaBaro.cpp :\u00c2\u00a0 **********************<\/p>\n

\/*
\n* Interface to Intersema Barometric pressure sensor.
\n* For the moment, only the MS5534C is supported.
\n* Others might be added in the future, especially the one with I2C.
\n*
\n* Created 14 Jan 2010
\n* By Richard Ulrich
\n* Inspired by the work of Hari Nair
\n*\/<\/p>\n

#include “IntersemaBaro.h”
\n\/\/#include “cppfix.h”<\/p>\n

\/\/using namespace Intersema;<\/p>\n

\/** @brief Constructur initializes the pins, reads the coefficients and reads a first altutude measurement. *\/
\nBaroPressure_MS5534C::BaroPressure_MS5534C(uint8_t pinMCLK, uint8_t pinSCLK, uint8_t pinDIN, uint8_t pinDOUT)
\n: pinMCLK_(pinMCLK), pinSCLK_(pinSCLK), pinDIN_(pinDIN), pinDOUT_(pinDOUT)
\n{<\/p>\n

}<\/p>\n

\/** @brief initialization function that has to be called in the setup() function. *\/
\nvoid BaroPressure_MS5534C::begin()
\n{
\n\/\/ set the pin directions
\npinMode(pinMCLK_, OUTPUT);
\npinMode(pinSCLK_, OUTPUT);
\npinMode(pinDIN_,\u00c2\u00a0 OUTPUT);
\npinMode(pinDOUT_, INPUT);<\/p>\n

\/\/ generate approx 34kHz square for pinMCLK_
\ntone(pinMCLK_, 31250);<\/p>\n

\/\/ configure the sensor
\nResetSensor();
\nReadCoefficients();<\/p>\n

\/\/ initialize
\nlong alt = AcquireAveragedSampleCm(NUM_SAMP_FOR_AVG);
\nTriggerTemperatureSample();
\nSensorState_ = SENSOR_READ_TEMPERATURE;
\n}<\/p>\n

void BaroPressure_MS5534C::ResetSensor()
\n{
\nSendCommand(0x155540, 21); \/\/ 1010101010101010 + 00000
\n}<\/p>\n

void BaroPressure_MS5534C::ReadCoefficients(void)
\n{
\nunsigned int wa = ReadCoefficient(0x15);
\nunsigned int wb = ReadCoefficient(0x16);
\ncoefficients_[0] = (unsigned int)((wa >> 1) & (unsigned int)0x7FFF);
\ncoefficients_[4] = (unsigned int)(((wa & 0x1) << 10) | ((wb >> 6) & (unsigned int)0x3FF));
\ncoefficients_[5] = (unsigned int)(wb & 0x3F);<\/p>\n

wa = ReadCoefficient(0x19);
\nwb = ReadCoefficient(0x1A);
\ncoefficients_[3] = (unsigned int)((wa >> 6) & 0x3FF);
\ncoefficients_[1] = (unsigned int)(((wa & 0x3F) << 6) | (wb & 0x3F));
\ncoefficients_[2] = (unsigned int)((wb >> 6) & 0x3FF);<\/p>\n

#ifdef DEBUG
\n\/\/\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0 for(size_t i=0; i<6; ++i)
\n\/\/\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0 {
\n\/\/\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0 Serial.print(“Coefficient “);
\n\/\/\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0 Serial.print(i + 1, DEC);
\n\/\/\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0 Serial.print(” : “);
\n\/\/\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0 \u00c2\u00a0\u00c2\u00a0\u00c2\u00a0 \u00c2\u00a0\u00c2\u00a0\u00c2\u00a0 Serial.println(coefficients_[i], DEC);
\n\/\/\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0 }
\n#endif
\n}<\/p>\n

size_t BaroPressure_MS5534C::ReadCoefficient(unsigned char addr)
\n{
\n\/\/ 111 + 6bit coeff addr + 000 + 1clk(send0)
\nunsigned long cmd = (unsigned long)0x1C00 | (((unsigned long)addr) << 4);
\nSendCommand(cmd,13);
\nreturn ReadWord();
\n}<\/p>\n

\/\/ send command MS bit first
\nvoid BaroPressure_MS5534C::SendCommand(unsigned long cmd, size_t nbits)
\n{
\nwhile(nbits–)
\n{
\nif(cmd & (unsigned long)(1 << nbits))
\ndigitalWrite(pinDIN_, HIGH);
\nelse
\ndigitalWrite(pinDIN_, LOW);<\/p>\n

digitalWrite(pinSCLK_, HIGH);
\ndigitalWrite(pinSCLK_, LOW);
\n}
\n}<\/p>\n

unsigned int BaroPressure_MS5534C::ReadWord(void)
\n{
\nunsigned int w;
\nunsigned int clk = 16;
\nw = 0;
\nwhile(clk–)
\n{
\ndigitalWrite(pinSCLK_, HIGH);
\ndigitalWrite(pinSCLK_, LOW);
\nw |=\u00c2\u00a0 (digitalRead(pinDOUT_) << clk);
\n}
\ndigitalWrite(pinSCLK_, HIGH);
\ndigitalWrite(pinSCLK_, LOW);<\/p>\n

return w;
\n}<\/p>\n

long BaroPressure_MS5534C::AcquireAveragedSampleCm(const size_t nSamples)
\n{
\nlong pressAccum = 0;<\/p>\n

for(size_t n = nSamples; n; n–)
\n{
\nTriggerTemperatureSample();
\nwhile(digitalRead(pinDOUT_))
\n;
\nconst unsigned int temperature = ReadWord();
\nTriggerPressureSample();
\nwhile(digitalRead(pinDOUT_))
\n;
\nconst unsigned int pressure = ReadWord(); \/\/ read pressure
\npressAccum += ConvertPressureTemperature(pressure, temperature);
\n}
\nlong pressAvg = pressAccum \/ nSamples;
\nlong AltCm\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0 = PascalToCentimeter(pressAvg * 10);<\/p>\n

return AltCm;
\n}<\/p>\n

long BaroPressure_MS5534C::ConvertPressureTemperature(unsigned int pressure, unsigned int temperature)
\n{
\nconst long UT1\u00c2\u00a0 = (coefficients_[4] << 3) + 20224;
\nconst long dT\u00c2\u00a0\u00c2\u00a0 = (long)temperature\u00c2\u00a0 – UT1;
\nconst long TEMP = 200 + ((dT * (coefficients_[5] + 50)) >> 10);
\nconst long OFF\u00c2\u00a0 = (coefficients_[1] <<2) + (((coefficients_[3] -512) * dT) >> 12);
\nconst long SENS = coefficients_[0]\u00c2\u00a0 + ((coefficients_[2] * dT) >> 10)\u00c2\u00a0 + 24576;
\nconst long X\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0 = ((SENS* ((long)pressure\u00c2\u00a0 – 7168)) >> 14) – OFF;
\npressure\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0 = ((X * 10) >> 5) + 2500;
\ntemperature = TEMP;<\/p>\n

long T2 = 0, P2 = 0;
\nif(TEMP < 200)
\n{
\nT2 = (11 * (coefficients_[5] + 24) * (200 – TEMP) * (200 – TEMP)) >> 20;
\nP2 = (3 * T2 * (pressure – 3500)) >> 14;
\npressure\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0 = pressure – P2;
\ntemperature = temperature – T2;
\n}<\/p>\n

return pressure;
\n}<\/p>\n

void BaroPressure_MS5534C::TriggerTemperatureSample(void)
\n{
\n\/\/ 111 + 1001 + 000 + 2clks(send 0)
\nResetSensor();
\nSendCommand(0xF20, 12);
\n}<\/p>\n

void BaroPressure_MS5534C::TriggerPressureSample(void)
\n{
\n\/\/ 111 + 1010 + 000 + 2clks(send 0)
\nResetSensor();
\nSendCommand(0xF40, 12);
\n}<\/p>\n

long BaroPressure_MS5534C::PascalToCentimeter(long pressurePa)
\n{
\n\/\/ Lookup table converting pressure in Pa to altitude in cm.
\n\/\/ Each LUT entry is the altitude in cm corresponding to an implicit
\n\/\/ pressure value, calculated as [PA_INIT – 1024*index] in Pa.
\n\/\/ The table is calculated for a nominal sea-level pressure\u00c2\u00a0 = 101325 Pa.
\nstatic const size_t PZLUT_ENTRIES = 77;
\nstatic const size_t PA_INIT\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0 = 104908;
\nstatic const size_t PA_DELTA\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0\u00c2\u00a0 = 1024;<\/p>\n

static const long lookupTable[PZLUT_ENTRIES] = {
\n-29408, -21087, -12700,\u00c2\u00a0 -4244,\u00c2\u00a0\u00c2\u00a0 4279,
\n12874,\u00c2\u00a0 21541,\u00c2\u00a0 30281,\u00c2\u00a0 39095,\u00c2\u00a0 47986,
\n56953,\u00c2\u00a0 66000,\u00c2\u00a0 75126,\u00c2\u00a0 84335,\u00c2\u00a0 93628,
\n103006, 112472, 122026, 131672, 141410,
\n151244, 161174, 171204, 181335, 191570,
\n201911, 212361, 222922, 233597, 244388,
\n255300, 266334, 277494, 288782, 300204,
\n311761, 323457, 335297, 347285, 359424,
\n371719, 384174, 396795, 409586, 422552,
\n435700, 449033, 462560, 476285, 490216,
\n504360, 518724, 533316, 548144, 563216,
\n578543, 594134, 609999, 626149, 642595,
\n659352, 676431, 693847, 711615, 729752,
\n748275, 767202, 786555, 806356, 826627,
\n847395, 868688, 890537, 912974, 936037,
\n959766, 984206};<\/p>\n

if(pressurePa > PA_INIT)
\nreturn lookupTable[0];
\nelse
\n{
\nconst long inx = (PA_INIT – pressurePa) >> 10;
\nif(inx >= PZLUT_ENTRIES – 1)
\nreturn lookupTable[PZLUT_ENTRIES – 1];
\nelse
\n{
\nconst long pa1 = PA_INIT – (inx << 10);
\nconst long z1 = lookupTable[inx];
\nconst long z2 = lookupTable[inx+1];
\nreturn (z1 + (((pa1 – pressurePa) * (z2 – z1)) >> 10));
\n}
\n}
\n}<\/p>\n","protected":false},"excerpt":{"rendered":"

After receiving personal messages on the arduino forum asking for the code for the Intersema pressure sensor, I paste my code here. It is based on the code from Hari Nair for the open source solar vario that I bought from him.<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[6,1],"tags":[19,168],"class_list":["post-10","post","type-post","status-publish","format-standard","hentry","category-projects","category-uncategorized","tag-arduino","tag-paragliding"],"_links":{"self":[{"href":"https:\/\/ulrichard.ch\/blog\/index.php?rest_route=\/wp\/v2\/posts\/10","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ulrichard.ch\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ulrichard.ch\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ulrichard.ch\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/ulrichard.ch\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=10"}],"version-history":[{"count":0,"href":"https:\/\/ulrichard.ch\/blog\/index.php?rest_route=\/wp\/v2\/posts\/10\/revisions"}],"wp:attachment":[{"href":"https:\/\/ulrichard.ch\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=10"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ulrichard.ch\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=10"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ulrichard.ch\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=10"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}