Device driver for Si7020 Digital humidity and temperature sensor.
Dependents: Si7020_example MAXWSNENV_sensors MAXWSNENV_sensors Hello-Uzuki-sensor-shield ... more
Si7020 Device Driver
This is a device driver for the Si7020 Humidity and temperature sensor. It uses I2C to communicate humidity and temperature data.
Si7020.cpp
- Committer:
- kgills
- Date:
- 2015-04-17
- Revision:
- 1:eca9d19c17ab
- Parent:
- 0:9a1febb56203
File content as of revision 1:eca9d19c17ab:
/******************************************************************************* * Copyright (C) 2015 Maxim Integrated Products, Inc., All Rights Reserved. * * Permission is hereby granted, free of charge, to any person obtaining a * copy of this software and associated documentation files (the "Software"), * to deal in the Software without restriction, including without limitation * the rights to use, copy, modify, merge, publish, distribute, sublicense, * and/or sell copies of the Software, and to permit persons to whom the * Software is furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be included * in all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. * IN NO EVENT SHALL MAXIM INTEGRATED BE LIABLE FOR ANY CLAIM, DAMAGES * OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR * OTHER DEALINGS IN THE SOFTWARE. * * Except as contained in this notice, the name of Maxim Integrated * Products, Inc. shall not be used except as stated in the Maxim Integrated * Products, Inc. Branding Policy. * * The mere transfer of this software does not imply any licenses * of trade secrets, proprietary technology, copyrights, patents, * trademarks, maskwork rights, or any other form of intellectual * property whatsoever. Maxim Integrated Products, Inc. retains all * ownership rights. ******************************************************************************* */ #include "Si7020.h" /***** Definitions *****/ #define I2C_ADDR (0x80) // 1000000x #define POLYVAL (0x131) /***** File Scope Data *****/ static const char cmd_meas_humid[] = { 0xE5 }; static const char cmd_meas_humid_no_hold[] = { 0xF5 }; static const char cmd_meas_temp[] = { 0xE3 }; static const char cmd_meas_temp_no_hold[] = { 0xF3 }; static const char cmd_meas_prev_temp[] = { 0xE0 }; static const char cmd_rst[] = { 0xFE }; static const char cmd_write_user1[] = { 0xE6 }; static const char cmd_read_user1[] = { 0xE7 }; static const char cmd_id_1[] = { 0xFA, 0x0F }; static const char cmd_id_2[] = { 0xFC, 0xC9 }; static const char cmd_fw_ver[] = { 0x84, 0xB8 }; //****************************************************************************** Si7020::Si7020(PinName sda, PinName scl) { i2c_ = new I2C(sda, scl); i2c_owner = true; // 400KHz, as specified by the datasheet. i2c_->frequency(400000); } //****************************************************************************** Si7020::Si7020(I2C *i2c) : i2c_(i2c) { i2c_owner = false; } //****************************************************************************** Si7020::~Si7020() { if(i2c_owner) { delete i2c_; } } //****************************************************************************** int Si7020::reset(void) { if (i2c_->write(I2C_ADDR, cmd_rst, sizeof(cmd_rst)) != 0) { return -1; } return 0; } //****************************************************************************** int Si7020::getElectronicId(char* id) { // Send cmd with repeated start if (i2c_->write(I2C_ADDR, cmd_id_1, sizeof(cmd_id_1), true) != 0) { return -1; } // Read first portion of ID char temp[8]; if (i2c_->read(I2C_ADDR, temp, 8, false) != 0) { return -1; } // Check the CRC char crc = 0; int i; for(i = 0; i < 4; i++) { crc = crc8(temp[2*i], crc); if(crc != temp[2*i +1]) { return -1; } } // Save top portion of ID id[7] = temp [0]; id[6] = temp [2]; id[5] = temp [4]; id[4] = temp [6]; // Send cmd with repeated start if (i2c_->write(I2C_ADDR, cmd_id_2, sizeof(cmd_id_2), true) != 0) { return -1; } // Read rest of ID if (i2c_->read(I2C_ADDR, temp, 6, false) != 0) { return -1; } // Check the CRC crc = 0; for(i = 0; i < 2; i++) { crc = crc8(temp[3*i], crc); crc = crc8(temp[3*i + 1], crc); if(crc != temp[3*i + 2]) { return -1; } } // Save bottom portion of ID id[3] = temp [0]; id[2] = temp [1]; id[1] = temp [3]; id[0] = temp [4]; return 0; } //****************************************************************************** int Si7020::configResolution(Si7020::resolution_t resolution) { char data[2]; if (i2c_->write(I2C_ADDR, cmd_read_user1, sizeof(cmd_read_user1)) != 0) { return -1; } if (i2c_->read(I2C_ADDR, &data[1], 1) != 0) { return -1; } switch (resolution) { case RH_12b_TEMP_14b: data[1] &= ~0x81; break; case RH_8b_TEMP_12b: data[1] = (data[1] & ~0x80) | 0x01; break; case RH_10b_TEMP_13b: data[1] = (data[1] & ~0x01) | 0x80; break; case RH_11b_TEMP_11b: data[1] |= 0x81; break; default: return -1; } data[0] = cmd_write_user1[0]; if (i2c_->write(I2C_ADDR, data, 2) != 0) { return -1; } return 0; } //****************************************************************************** int Si7020::getTemperature(int16_t *tempCx10) { if (i2c_->write(I2C_ADDR, cmd_meas_temp, sizeof(cmd_meas_temp)) != 0) { return -1; } return checkTemperature(tempCx10); } //****************************************************************************** int Si7020::getTemperature(float *tempC) { if (i2c_->write(I2C_ADDR, cmd_meas_temp, sizeof(cmd_meas_temp)) != 0) { return -1; } return checkTemperature(tempC); } //****************************************************************************** int Si7020::startTemperature(void) { if (i2c_->write(I2C_ADDR, cmd_meas_temp_no_hold, sizeof(cmd_meas_temp_no_hold)) != 0) { return -1; } return 0; } //****************************************************************************** int Si7020::checkTemperature(int16_t *tempCx10) { char data[3]; uint16_t code; int temp; if (i2c_->read(I2C_ADDR, data, 3) != 0) { return -1; } // Get 16-bit value from bytes read code = ((uint16_t)data[0] << 8) + data[1]; // Calculate the temperature using the formula from the datasheet // Scaled by 100 temp = ((((int)17572 * code) + 0x8000) >> 16) - 4685; // Return value is to be scaled by 10 *tempCx10 = (temp + 5) / 10; return 0; } //****************************************************************************** int Si7020::checkTemperature(float *tempC) { char data[3]; uint16_t code; if (i2c_->read(I2C_ADDR, data, 3) != 0) { return -1; } // Get 16-bit value from bytes read code = ((uint16_t)data[0] << 8) + data[1]; // Calculate the temperature using the formula from the datasheet // Scaled by 100 *tempC = ((175.72f * (float)code) / 65536.0f) - 46.85f; return 0; } //****************************************************************************** int Si7020::getHumidity(int16_t *humidx10) { if (i2c_->write(I2C_ADDR, cmd_meas_humid, sizeof(cmd_meas_humid), true) != 0) { return -1; } return checkHumidity(humidx10); } //****************************************************************************** int Si7020::getHumidity(float *humid) { if (i2c_->write(I2C_ADDR, cmd_meas_humid, sizeof(cmd_meas_humid)) != 0) { return -1; } return checkHumidity(humid); } //****************************************************************************** int Si7020::startHumidity(void) { if (i2c_->write(I2C_ADDR, cmd_meas_humid_no_hold, sizeof(cmd_meas_humid_no_hold)) != 0) { return -1; } return 0; } //****************************************************************************** int Si7020::checkHumidity(int16_t *humidx10) { char data[3]; uint16_t code; if (i2c_->read(I2C_ADDR, data, 3) != 0) { return -1; } // Get 16-bit value from bytes read code = ((uint16_t)data[0] << 8) + data[1]; // Calculate the humidity using the formula from the datasheet // Scaled by 10 *humidx10 = ((((int)1250 * code) + 0x8000) >> 16) - 60; // Check the crc char crc = crc8(data[0], 0x00); crc = crc8(data[1], crc); if(crc != data[2]) { return -1; } return 0; } //****************************************************************************** int Si7020::checkHumidity(float *humid) { char data[3]; uint16_t code; if (i2c_->read(I2C_ADDR, data, 3) != 0) { return -1; } // Get 16-bit value from bytes read code = ((uint16_t)data[0] << 8) + data[1]; // Calculate the humidity using the formula from the datasheet *humid = ((125.0f * (float)code) / 65536.0f) - 6.0f; return 0; } //****************************************************************************** int Si7020::getPrevTemperature(float *tempC) { if (i2c_->write(I2C_ADDR, cmd_meas_prev_temp, sizeof(cmd_meas_prev_temp)) != 0) { return -1; } if(checkTemperature(tempC) != 0) { return -1; } return 0; } //****************************************************************************** int Si7020::getPrevTemperature(int16_t *tempCx10) { if (i2c_->write(I2C_ADDR, cmd_meas_prev_temp, sizeof(cmd_meas_prev_temp)) != 0) { return -1; } if(checkTemperature(tempCx10) != 0) { return -1; } return 0; } //****************************************************************************** int Si7020::getRev(char *rev) { if (i2c_->write(I2C_ADDR, cmd_fw_ver, sizeof(cmd_fw_ver)) != 0) { return -1; } if (i2c_->read(I2C_ADDR, rev, 1) != 0) { return -1; } return 0; } //****************************************************************************** int Si7020::heater(bool enable) { char data[2]; if (i2c_->write(I2C_ADDR, cmd_read_user1, sizeof(cmd_read_user1)) != 0) { return -1; } if (i2c_->read(I2C_ADDR, &data[1], 1) != 0) { return -1; } if (enable) { data[1] |= 0x04; } else { data[1] &= ~0x04; } data[0] = cmd_write_user1[0]; if (i2c_->write(I2C_ADDR, data, 2) != 0) { return -1; } return 0; } //****************************************************************************** char Si7020::crc8(char value, char seed) { int i; for (i = 0; i < 8; i++) { if ((value ^ seed) & 0x80) { seed <<= 1; seed ^= POLYVAL; } else { seed <<= 1; } value <<= 1; } return seed; }