Interface to a Silicon Labs Si7005 relative humidity sensor.
Diff: Si7005.cpp
- Revision:
- 0:6fbf67893ca2
diff -r 000000000000 -r 6fbf67893ca2 Si7005.cpp --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/Si7005.cpp Wed Apr 10 08:43:56 2013 +0000 @@ -0,0 +1,136 @@ +/* mbed Si7005 relative humidity sensor Library + * + * Copyright (c) 2013, Lieven Hollevoet (http://likatronix.be) + * + * 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 THE + * AUTHORS OR COPYRIGHT HOLDERS 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. + */ + + +#include "Si7005.h" +#include "mbed.h" + +/* + Constructor, pin names for I2C of the device + */ +Si7005::Si7005(PinName scl, PinName sda) + : _i2c(scl, sda) { + + _i2c.frequency(50000); + _addr = 0x80; +} + + +int Si7005::readID(void) { + int data; + + data = _read(SI7005_REG_ID); + + return data; + +} + +void Si7005::startMeasurement(char type) { + char command; + + switch (type) { + case SI7005_RH: + command = 0x01; // Start relative humidity measurement + break; + case SI7005_T: + command = 0x11; // Start temperature measurement + break; + default: + return; + } + + _write(SI7005_REG_CONFIG, command); + + return; +} + +bool Si7005::conversionDone(void) { + int result; + result = _read(SI7005_REG_STATUS); + + if (result == 0) { + return true; + } else { + return false; + } + +} + +int Si7005::readResult(char type) { + int result; + float f_res; + float f_lin; + + result = _read_int(SI7005_REG_DATAH); + + switch (type) { + case SI7005_RH: + // Keep upper 12 bits + result = result >> 4; + // Calculate % + f_res = ((float)result / 16) - 24; + // Linearize + f_lin = f_res - ((f_res * f_res) * - 0.00393 + f_res * 0.4008 - 4.7844 ); + return (int)f_lin; + case SI7005_T: + // Keep upper 14 bits + result = result >> 2; + // Calculate % + result = (result / 32) - 50; + return result; + default: + return -1; + } +} +// private functions for low level IO +// The Si7005 needs a restart bit when doing read accesses + +void Si7005::_write(int reg, int data) { + char args[2]; + args[0] = reg; + args[1] = data; + _i2c.write(_addr, args,2); +} + +int Si7005::_read(int reg) { + char args[2]; + args[0] = reg; + _i2c.write(_addr, args, 1, true); // No stop condition here + _i2c.read(_addr, args, 1, true); // And a restart condition here + _i2c.stop(); + return(args[0]); +} + +int Si7005::_read_int(int reg) { + char data[2]; + data[0] = reg; + _i2c.write(_addr, data, 1, true); // No stop condition here + _i2c.read(_addr, data, 2, true); // And a restart condition here + _i2c.stop(); + + // Data is read out MSB first + + return ((data[0] << 8) + data[1]); + +} +