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| Rev | Author | Line No. | Line |
|---|---|---|---|
| 5 | mjames | 1 | //============================================================================== |
| 2 | // E - R A D I O N I C A . C O M, H.Kolomana 6/A, Djakovo 31400, Croatia |
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| 3 | //============================================================================== |
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| 4 | // Project : SHT21 Arduino Library (V1.0) |
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| 5 | // File : SHT21.cpp |
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| 6 | // Author : e-radionica.com 2017 |
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| 7 | // Licence : Open-source ! |
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| 8 | //============================================================================== |
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| 9 | //============================================================================== |
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| 10 | // Use with any SHT21 breakout. Check ours: |
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| 11 | // https://e-radionica.com/en/sht21-humidity-and-temperature-sensor.html |
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| 12 | // If any questions, |
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| 13 | // just contact techsupport@e-radionica.com |
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| 14 | //============================================================================== |
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| 15 | |||
| 16 | |||
| 17 | // Modified for ChibiOS Mike James Feb 2020 |
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| 18 | #include "ch.h" |
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| 19 | #include <SHT21.h> |
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| 20 | |||
| 21 | |||
| 22 | //============================================================================== |
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| 23 | // PUBLIC |
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| 24 | //============================================================================== |
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| 25 | float SHT21::getHumidity(void) { |
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| 26 | uint16_t result; // return variable |
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| 27 | |||
| 28 | result = readSensor_hm(TRIGGER_RH_MEASUREMENT_HM); |
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| 29 | |||
| 30 | return CalcRH(result); |
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| 31 | } |
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| 32 | |||
| 33 | float SHT21::getTemperature(void) { |
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| 34 | uint16_t result; // return variable |
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| 35 | |||
| 36 | result = readSensor_hm(TRIGGER_T_MEASUREMENT_HM); |
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| 37 | |||
| 38 | return CalcT(result); |
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| 39 | } |
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| 40 | |||
| 41 | void SHT21::reset() { |
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| 42 | |||
| 43 | |||
| 44 | const uint8_t buff = SOFT_RESET; |
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| 6 | mjames | 45 | msg_t err = i2cMasterTransmit(m_driver, I2C_ADD, &buff, sizeof(buff), 0,0); |
| 5 | mjames | 46 | if(err != MSG_OK) |
| 47 | |||
| 48 | |||
| 6 | mjames | 49 | chThdSleepMilliseconds(15); // wait for SHT to reset |
| 5 | mjames | 50 | } |
| 51 | |||
| 52 | msg_t SHT21::getSerialNumber(uint8_t * serialNumber) { |
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| 53 | |||
| 54 | |||
| 55 | // read memory location 1 |
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| 6 | mjames | 56 | const uint8_t buff []= { 0xFA,0x0F }; |
| 5 | mjames | 57 | |
| 6 | mjames | 58 | uint8_t rxbuff[8]; |
| 59 | msg_t err = i2cMasterTransmit(m_driver, I2C_ADD, buff, sizeof(buff), &rxbuff[0], sizeof(rxbuff)); |
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| 5 | mjames | 60 | if(err != MSG_OK) |
| 6 | mjames | 61 | return err; |
| 5 | mjames | 62 | |
| 6 | mjames | 63 | serialNumber[5] = rxbuff[0]; // read SNB_3 |
| 5 | mjames | 64 | // CRC SNB_3 not used |
| 6 | mjames | 65 | serialNumber[4] = rxbuff[2]; // read SNB_2 |
| 5 | mjames | 66 | // CRC SNB_2 not used |
| 6 | mjames | 67 | serialNumber[3] = rxbuff[4]; // read SNB_1 |
| 5 | mjames | 68 | // CRC SNB_1 not used |
| 6 | mjames | 69 | serialNumber[2] = rxbuff[7]; // read SNB_0 |
| 5 | mjames | 70 | // CRC SNB_0 not used |
| 71 | |||
| 72 | // read memory location 2 |
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| 6 | mjames | 73 | const uint8_t buff2[] = {0xFC,0xC9}; |
| 5 | mjames | 74 | |
| 6 | mjames | 75 | err = i2cMasterTransmit(m_driver, I2C_ADD, buff2, sizeof(buff2), &rxbuff[0], 6); |
| 5 | mjames | 76 | |
| 77 | |||
| 6 | mjames | 78 | serialNumber[1] = rxbuff[0]; // read SNC_1 |
| 79 | serialNumber[0] = rxbuff[1]; // read SNC_0 |
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| 80 | serialNumber[7] = rxbuff[3]; // read SNA_1 |
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| 81 | serialNumber[6] = rxbuff[4]; // read SNA_0 |
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| 5 | mjames | 82 | |
| 6 | mjames | 83 | return MSG_OK; |
| 5 | mjames | 84 | } |
| 85 | |||
| 86 | //============================================================================== |
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| 87 | // PRIVATE |
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| 88 | //============================================================================== |
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| 89 | |||
| 90 | uint16_t SHT21::readSensor_hm(uint8_t command) { |
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| 91 | uint8_t checksum; |
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| 92 | uint8_t data[2]; |
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| 93 | uint16_t result; |
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| 94 | |||
| 95 | uint8_t rxBuff[3]; |
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| 6 | mjames | 96 | |
| 97 | msg_t err = i2cMasterTransmit(m_driver, I2C_ADD, &command, 1, &rxBuff[0], 3); |
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| 5 | mjames | 98 | if (err != MSG_OK) |
| 99 | |||
| 100 | data[0] = rxBuff[0]; // read data (MSB) |
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| 101 | data[1] = rxBuff[1]; // read data (LSB) |
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| 102 | checksum = rxBuff[2]; // read checksum |
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| 103 | |||
| 104 | result = (data[0] << 8); |
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| 105 | result += data[1]; |
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| 106 | |||
| 107 | if(CRC_Checksum (data,2,checksum)) { |
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| 108 | reset(); |
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| 109 | return 1; |
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| 110 | } |
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| 111 | |||
| 112 | else return result; |
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| 113 | } |
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| 114 | |||
| 115 | float SHT21::CalcRH(uint16_t rh) { |
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| 116 | |||
| 117 | rh &= ~0x0003; // clean last two bits |
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| 118 | |||
| 119 | return (-6.0 + 125.0/65536 * (float)rh); // return relative humidity |
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| 120 | } |
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| 121 | |||
| 122 | float SHT21::CalcT(uint16_t t) { |
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| 123 | |||
| 124 | t &= ~0x0003; // clean last two bits |
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| 125 | |||
| 126 | return (-46.85 + 175.72/65536 * (float)t); |
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| 127 | } |
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| 128 | |||
| 129 | uint8_t SHT21::CRC_Checksum(uint8_t data[], uint8_t no_of_bytes, uint8_t checksum) { |
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| 130 | uint8_t crc = 0; |
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| 131 | uint8_t byteCtr; |
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| 132 | |||
| 133 | //calculates 8-Bit checksum with given polynomial |
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| 134 | for (byteCtr = 0; byteCtr < no_of_bytes; ++byteCtr) |
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| 135 | { crc ^= (data[byteCtr]); |
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| 136 | for (uint8_t bit = 8; bit > 0; --bit) |
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| 137 | { if (crc & 0x80) crc = (crc << 1) ^ POLYNOMIAL; |
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| 138 | else crc = (crc << 1); |
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| 139 | } |
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| 140 | } |
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| 141 | if (crc != checksum) return 1; |
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| 142 | else return 0; |
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| 143 | } |
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| 144 | |||
| 145 |