Oscar Silva / Sht31

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Fork of Sht31 by Andrea Corrado

Sht31.cpp@3:c4bd8cd5d566, 2018-10-03 (annotated)

Committer:
osilvam
Date:
Wed Oct 03 13:51:56 2018 +0000
Revision:
3:c4bd8cd5d566
Parent:
2:c84a60326ecf 
first commit

Who changed what in which revision?

UserRevisionLine numberNew contents of line
GeofferyOmlette 0:c90aa4f69539 1 /***************************************************
GeofferyOmlette 0:c90aa4f69539 2 This is a library for the SHT31 Digital Humidity & Temp Sht31
GeofferyOmlette 0:c90aa4f69539 3
GeofferyOmlette 0:c90aa4f69539 4 Designed specifically to work with the SHT31 Digital Sht31 from Adafruit
GeofferyOmlette 0:c90aa4f69539 5 ----> https://www.adafruit.com/products/2857
GeofferyOmlette 0:c90aa4f69539 6
GeofferyOmlette 0:c90aa4f69539 7 These displays use I2C to communicate, 2 pins are required to
GeofferyOmlette 0:c90aa4f69539 8 interface
GeofferyOmlette 0:c90aa4f69539 9 Adafruit invests time and resources providing this open source code,
GeofferyOmlette 0:c90aa4f69539 10 please support Adafruit and open-source hardware by purchasing
GeofferyOmlette 0:c90aa4f69539 11 products from Adafruit!
GeofferyOmlette 0:c90aa4f69539 12
GeofferyOmlette 0:c90aa4f69539 13 Written by Limor Fried/Ladyada for Adafruit Industries.
GeofferyOmlette 0:c90aa4f69539 14 BSD license, all text above must be included in any redistribution
GeofferyOmlette 0:c90aa4f69539 15 ****************************************************/
GeofferyOmlette 0:c90aa4f69539 16
GeofferyOmlette 0:c90aa4f69539 17 #include "Sht31.h"
GeofferyOmlette 0:c90aa4f69539 18 #include "mbed.h"
GeofferyOmlette 0:c90aa4f69539 19
osilvam 3:c4bd8cd5d566 20 Sht31::Sht31(PinName sda, PinName scl, bool i2caddr) : _i2c(sda, scl) {
osilvam 3:c4bd8cd5d566 21 _i2caddr = !i2caddr ? (0x44 << 1) : (0x45 << 1);
GeofferyOmlette 0:c90aa4f69539 22 reset();
GeofferyOmlette 0:c90aa4f69539 23 readStatus();
GeofferyOmlette 0:c90aa4f69539 24 }
GeofferyOmlette 0:c90aa4f69539 25
GeofferyOmlette 0:c90aa4f69539 26 float Sht31::readTemperature(void) {
GeofferyOmlette 0:c90aa4f69539 27 if (! readTempHum()) return NAN;
GeofferyOmlette 0:c90aa4f69539 28 return temp;
GeofferyOmlette 0:c90aa4f69539 29 }
GeofferyOmlette 0:c90aa4f69539 30
GeofferyOmlette 0:c90aa4f69539 31 float Sht31::readHumidity(void) {
GeofferyOmlette 0:c90aa4f69539 32 if (! readTempHum()) return NAN;
GeofferyOmlette 0:c90aa4f69539 33 return humidity;
GeofferyOmlette 0:c90aa4f69539 34 }
GeofferyOmlette 0:c90aa4f69539 35
GeofferyOmlette 0:c90aa4f69539 36 void Sht31::reset(void) {
GeofferyOmlette 1:756e26f0b067 37 writeCommand(SHT31_SOFTRESET);
GeofferyOmlette 0:c90aa4f69539 38 wait_ms(10);
GeofferyOmlette 0:c90aa4f69539 39 }
GeofferyOmlette 0:c90aa4f69539 40
GeofferyOmlette 0:c90aa4f69539 41 uint16_t Sht31::readStatus(void) {
GeofferyOmlette 0:c90aa4f69539 42 writeCommand(SHT31_READSTATUS);
GeofferyOmlette 0:c90aa4f69539 43 char val[1];
GeofferyOmlette 0:c90aa4f69539 44 _i2c.read(_i2caddr, val, 1);
GeofferyOmlette 0:c90aa4f69539 45 uint16_t stat = val[0];
GeofferyOmlette 0:c90aa4f69539 46 stat <<= 8;
GeofferyOmlette 0:c90aa4f69539 47 _i2c.read(_i2caddr, val, 1);
GeofferyOmlette 0:c90aa4f69539 48 stat |= val[0];
andcor02 2:c84a60326ecf 49 // printf("0x%X\r\n", stat);
GeofferyOmlette 0:c90aa4f69539 50 return stat;
GeofferyOmlette 0:c90aa4f69539 51 }
GeofferyOmlette 0:c90aa4f69539 52
GeofferyOmlette 0:c90aa4f69539 53 void Sht31::writeCommand(uint16_t cmd) {
GeofferyOmlette 0:c90aa4f69539 54 char buf[2];
GeofferyOmlette 0:c90aa4f69539 55 buf[0] = (cmd >> 8);
GeofferyOmlette 0:c90aa4f69539 56 buf[1] = (cmd & 0xFF);
GeofferyOmlette 0:c90aa4f69539 57 _i2c.write(_i2caddr, buf, 2);
GeofferyOmlette 0:c90aa4f69539 58 }
GeofferyOmlette 0:c90aa4f69539 59
GeofferyOmlette 0:c90aa4f69539 60 bool Sht31::readTempHum(void) {
GeofferyOmlette 0:c90aa4f69539 61 char readbuffer[6];
GeofferyOmlette 0:c90aa4f69539 62
GeofferyOmlette 0:c90aa4f69539 63 writeCommand(SHT31_MEAS_HIGHREP);
GeofferyOmlette 0:c90aa4f69539 64
GeofferyOmlette 0:c90aa4f69539 65 wait_ms(500);
GeofferyOmlette 0:c90aa4f69539 66 _i2c.read(_i2caddr, readbuffer, 6);
andcor02 2:c84a60326ecf 67
GeofferyOmlette 0:c90aa4f69539 68 uint16_t ST, SRH;
GeofferyOmlette 0:c90aa4f69539 69 ST = readbuffer[0];
GeofferyOmlette 0:c90aa4f69539 70 ST <<= 8;
GeofferyOmlette 0:c90aa4f69539 71 ST |= readbuffer[1];
GeofferyOmlette 0:c90aa4f69539 72
GeofferyOmlette 0:c90aa4f69539 73 if (readbuffer[2] != crc8((uint8_t *) readbuffer, 2)) {
GeofferyOmlette 0:c90aa4f69539 74 return false;
GeofferyOmlette 0:c90aa4f69539 75 }
GeofferyOmlette 0:c90aa4f69539 76
GeofferyOmlette 0:c90aa4f69539 77 SRH = readbuffer[3];
GeofferyOmlette 0:c90aa4f69539 78 SRH <<= 8;
GeofferyOmlette 0:c90aa4f69539 79 SRH |= readbuffer[4];
GeofferyOmlette 0:c90aa4f69539 80
GeofferyOmlette 0:c90aa4f69539 81 if (readbuffer[5] != crc8((uint8_t *) readbuffer+3, 2)) {
GeofferyOmlette 0:c90aa4f69539 82 return false;
GeofferyOmlette 0:c90aa4f69539 83 }
GeofferyOmlette 0:c90aa4f69539 84
GeofferyOmlette 0:c90aa4f69539 85 double stemp = ST;
GeofferyOmlette 0:c90aa4f69539 86 stemp *= 175;
GeofferyOmlette 0:c90aa4f69539 87 stemp /= 0xffff;
GeofferyOmlette 0:c90aa4f69539 88 stemp = -45 + stemp;
GeofferyOmlette 0:c90aa4f69539 89 temp = stemp;
GeofferyOmlette 0:c90aa4f69539 90
GeofferyOmlette 0:c90aa4f69539 91 double shum = SRH;
GeofferyOmlette 0:c90aa4f69539 92 shum *= 100;
GeofferyOmlette 0:c90aa4f69539 93 shum /= 0xFFFF;
GeofferyOmlette 0:c90aa4f69539 94
GeofferyOmlette 0:c90aa4f69539 95 humidity = shum;
GeofferyOmlette 0:c90aa4f69539 96
GeofferyOmlette 0:c90aa4f69539 97 return true;
GeofferyOmlette 0:c90aa4f69539 98 }
GeofferyOmlette 0:c90aa4f69539 99
osilvam 3:c4bd8cd5d566 100
osilvam 3:c4bd8cd5d566 101 bool Sht31::readTempHum(float &_temp, float &_humidity) {
osilvam 3:c4bd8cd5d566 102 char readbuffer[6];
osilvam 3:c4bd8cd5d566 103
osilvam 3:c4bd8cd5d566 104 writeCommand(SHT31_MEAS_HIGHREP);
osilvam 3:c4bd8cd5d566 105
osilvam 3:c4bd8cd5d566 106 wait_ms(500);
osilvam 3:c4bd8cd5d566 107 _i2c.read(_i2caddr, readbuffer, 6);
osilvam 3:c4bd8cd5d566 108
osilvam 3:c4bd8cd5d566 109 uint16_t ST, SRH;
osilvam 3:c4bd8cd5d566 110 ST = readbuffer[0];
osilvam 3:c4bd8cd5d566 111 ST <<= 8;
osilvam 3:c4bd8cd5d566 112 ST |= readbuffer[1];
osilvam 3:c4bd8cd5d566 113
osilvam 3:c4bd8cd5d566 114 if (readbuffer[2] != crc8((uint8_t *) readbuffer, 2)) {
osilvam 3:c4bd8cd5d566 115 return false;
osilvam 3:c4bd8cd5d566 116 }
osilvam 3:c4bd8cd5d566 117
osilvam 3:c4bd8cd5d566 118 SRH = readbuffer[3];
osilvam 3:c4bd8cd5d566 119 SRH <<= 8;
osilvam 3:c4bd8cd5d566 120 SRH |= readbuffer[4];
osilvam 3:c4bd8cd5d566 121
osilvam 3:c4bd8cd5d566 122 if (readbuffer[5] != crc8((uint8_t *) readbuffer+3, 2)) {
osilvam 3:c4bd8cd5d566 123 return false;
osilvam 3:c4bd8cd5d566 124 }
osilvam 3:c4bd8cd5d566 125
osilvam 3:c4bd8cd5d566 126 double stemp = ST;
osilvam 3:c4bd8cd5d566 127 stemp *= 175;
osilvam 3:c4bd8cd5d566 128 stemp /= 0xffff;
osilvam 3:c4bd8cd5d566 129 stemp = -45 + stemp;
osilvam 3:c4bd8cd5d566 130 temp = stemp;
osilvam 3:c4bd8cd5d566 131 _temp = temp;
osilvam 3:c4bd8cd5d566 132
osilvam 3:c4bd8cd5d566 133 double shum = SRH;
osilvam 3:c4bd8cd5d566 134 shum *= 100;
osilvam 3:c4bd8cd5d566 135 shum /= 0xFFFF;
osilvam 3:c4bd8cd5d566 136
osilvam 3:c4bd8cd5d566 137 humidity = shum;
osilvam 3:c4bd8cd5d566 138 _humidity = humidity;
osilvam 3:c4bd8cd5d566 139
osilvam 3:c4bd8cd5d566 140 return true;
osilvam 3:c4bd8cd5d566 141 }
osilvam 3:c4bd8cd5d566 142
osilvam 3:c4bd8cd5d566 143
GeofferyOmlette 0:c90aa4f69539 144 uint8_t Sht31::crc8(const uint8_t *data, int len) {
GeofferyOmlette 0:c90aa4f69539 145 const uint8_t POLYNOMIAL(0x31);
GeofferyOmlette 0:c90aa4f69539 146 uint8_t crc(0xFF);
GeofferyOmlette 0:c90aa4f69539 147
GeofferyOmlette 0:c90aa4f69539 148 for ( int j = len; j; --j ) {
GeofferyOmlette 0:c90aa4f69539 149 crc ^= *data++;
GeofferyOmlette 0:c90aa4f69539 150
GeofferyOmlette 0:c90aa4f69539 151 for ( int i = 8; i; --i ) {
GeofferyOmlette 0:c90aa4f69539 152 crc = (crc & 0x80) ? (crc << 1) ^ POLYNOMIAL : (crc << 1);
GeofferyOmlette 0:c90aa4f69539 153 }
GeofferyOmlette 0:c90aa4f69539 154 }
GeofferyOmlette 0:c90aa4f69539 155 return crc;
GeofferyOmlette 0:c90aa4f69539 156 }