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.
Diff: Si7020.cpp
- Revision:
- 0:9a1febb56203
- Child:
- 1:eca9d19c17ab
diff -r 000000000000 -r 9a1febb56203 Si7020.cpp --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/Si7020.cpp Fri Apr 17 09:53:45 2015 -0500 @@ -0,0 +1,424 @@ +/******************************************************************************* + * 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 = (((float)175.72 * code) / 65536) - 46.85; + + 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 = (((float)125 * code) / 65536) - 6; + + 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; +}