136 lines
3.3 KiB
C++
136 lines
3.3 KiB
C++
/*
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Copyright 2014 Marcus Sorensen <marcus@electron14.com>
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This program is licensed under the GNU GPL v2
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*/
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#include "Arduino.h"
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#include "SI7021.h"
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#include <Wire.h>
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#define I2C_ADDR 0x40
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// I2C commands
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byte RH_READ[] = { 0xE5 };
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byte TEMP_READ[] = { 0xE3 };
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byte POST_RH_TEMP_READ[] = { 0xE0 };
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byte RESET[] = { 0xFE };
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byte USER1_READ[] = { 0xE7 };
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byte USER1_WRITE[] = { 0xE6 };
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byte SERIAL1_READ[] = { 0xFA, 0x0F };
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byte SERIAL2_READ[] = { 0xFC, 0xC9 };
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bool _si_exists = false;
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SI7021::SI7021() {
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}
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bool SI7021::begin() {
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Wire.begin();
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Wire.beginTransmission(I2C_ADDR);
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if (Wire.endTransmission() == 0) {
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_si_exists = true;
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}
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return _si_exists;
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}
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bool SI7021::sensorExists() {
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return _si_exists;
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}
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int SI7021::getFahrenheitHundredths() {
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unsigned int c = getCelsiusHundredths();
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return (1.8 * c) + 3200;
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}
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int SI7021::getCelsiusHundredths() {
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byte tempbytes[2];
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_command(TEMP_READ, tempbytes);
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long tempraw = (long)tempbytes[0] << 8 | tempbytes[1];
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return ((17572 * tempraw) >> 16) - 4685;
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}
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int SI7021::_getCelsiusPostHumidity() {
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byte tempbytes[2];
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_command(POST_RH_TEMP_READ, tempbytes);
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long tempraw = (long)tempbytes[0] << 8 | tempbytes[1];
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return ((17572 * tempraw) >> 16) - 4685;
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}
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unsigned int SI7021::getHumidityPercent() {
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byte humbytes[2];
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_command(RH_READ, humbytes);
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long humraw = (long)humbytes[0] << 8 | humbytes[1];
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return ((125 * humraw) >> 16) - 6;
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}
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unsigned int SI7021::getHumidityBasisPoints() {
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byte humbytes[2];
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_command(RH_READ, humbytes);
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long humraw = (long)humbytes[0] << 8 | humbytes[1];
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return ((12500 * humraw) >> 16) - 600;
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}
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void SI7021::_command(byte * cmd, byte * buf ) {
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_writeReg(cmd, sizeof cmd);
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_readReg(buf, sizeof buf);
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}
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void SI7021::_writeReg(byte * reg, int reglen) {
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Wire.beginTransmission(I2C_ADDR);
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for(int i = 0; i < reglen; i++) {
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reg += i;
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Wire.write(*reg);
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}
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Wire.endTransmission();
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}
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int SI7021::_readReg(byte * reg, int reglen) {
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Wire.requestFrom(I2C_ADDR, reglen);
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while(Wire.available() < reglen) {
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}
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for(int i = 0; i < reglen; i++) {
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reg[i] = Wire.read();
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}
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return 1;
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}
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//note this has crc bytes embedded, per datasheet, so provide 12 byte buf
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int SI7021::getSerialBytes(byte * buf) {
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_writeReg(SERIAL1_READ, sizeof SERIAL1_READ);
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_readReg(buf, 6);
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_writeReg(SERIAL2_READ, sizeof SERIAL2_READ);
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_readReg(buf + 6, 6);
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// could verify crc here and return only the 8 bytes that matter
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return 1;
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}
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int SI7021::getDeviceId() {
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byte serial[12];
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getSerialBytes(serial);
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int id = serial[6];
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return id;
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}
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void SI7021::setHeater(bool on) {
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byte userbyte;
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if (on) {
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userbyte = 0x3E;
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} else {
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userbyte = 0x3A;
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}
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byte userwrite[] = {USER1_WRITE[0], userbyte};
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_writeReg(userwrite, sizeof userwrite);
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}
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// get humidity, then get temperature reading from humidity measurement
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struct si7021_env SI7021::getHumidityAndTemperature() {
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si7021_env ret = {0, 0, 0};
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ret.humidityPercent = getHumidityPercent();
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ret.celsiusHundredths = _getCelsiusPostHumidity();
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ret.fahrenheitHundredths = (1.8 * ret.celsiusHundredths) + 3200;
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return ret;
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}
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