STTS751.cpp

00001 /* A library for STMicroelectronics STTS751 I2C temperature sensor
00002  * Copyright 2014, Takuo WATANABE (wtakuo)
00003  *
00004  * Licensed under the Apache License, Version 2.0 (the "License");
00005  * you may not use this file except in compliance with the License.
00006  * You may obtain a copy of the License at
00007  *
00008  *   http://www.apache.org/licenses/LICENSE-2.0
00009  *
00010  * Unless required by applicable law or agreed to in writing, software
00011  * distributed under the License is distributed on an "AS IS" BASIS,
00012  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00013  * See the License for the specific language governing permissions and
00014  * limitations under the License.
00015  */
00016 
00017 #include "STTS751.h"
00018 
00019 #define SET_BITS(x,m,b) (((x) & ~(m)) | (b))
00020 
00021 STTS751::STTS751(PinName sda, PinName scl, bool standby, Address addr, Model model) :
00022         _i2c(sda, scl), _addr(addr | model), _standby(standby) {
00023     init();
00024 }
00025 
00026 STTS751::STTS751(I2C &i2c, bool standby, Address addr, Model model) :
00027         _i2c(i2c), _addr(addr | model), _standby(standby) {
00028     init();
00029 }
00030 
00031 void STTS751::init() {
00032     char conf = 0x00;
00033     if (_standby)
00034         conf |= CONF_RUNSTOP;
00035     write8(REG_CONFIGURATION, conf);
00036     // conversion rate = 1/sec
00037     write8(REG_CONV_RATE, 0x04);
00038 }
00039 
00040 int STTS751::addr() {
00041     return _addr;
00042 }
00043 
00044 STTS751::Resolution STTS751::resolution() {
00045     char conf = read8(REG_CONFIGURATION);
00046     return (STTS751::Resolution) (conf & CONF_RES_MASK);
00047 }
00048 
00049 void STTS751::setResolution(STTS751::Resolution res) {
00050     char conf = read8(REG_CONFIGURATION);
00051     conf = SET_BITS(conf, CONF_RES_MASK, res);
00052     write8(REG_CONFIGURATION, conf);
00053 }
00054 
00055 int STTS751::conversionRate() {
00056     char conv = read8(REG_CONV_RATE);
00057     return conv & CONV_RATE_MASK;
00058 }
00059 
00060 void STTS751::setConversionRate(int rate) {
00061     write8(REG_CONV_RATE, (char)(rate & CONV_RATE_MASK));
00062 }
00063 
00064 void STTS751::setStandbyMode(bool standby) {
00065     _standby = standby;
00066     char conf = read8(REG_CONFIGURATION);
00067     if (_standby)
00068         conf |= CONF_RUNSTOP;
00069     else
00070         conf &= ~CONF_RUNSTOP;
00071     write8(REG_CONFIGURATION, conf);
00072 }
00073 
00074 void STTS751::start() {
00075     if (ready())
00076         write8(REG_ONESHOT, 1);
00077 }
00078 
00079 bool STTS751::ready() {
00080     char status = read8(REG_STATUS);
00081     return (status & STATUS_BUSY) == 0;
00082 }
00083 
00084 float STTS751::temp(bool nowait) {
00085     if (_standby && !nowait) {
00086         start();
00087         while (!ready())
00088             wait(0.01);
00089     }
00090     signed char h = read8(REG_TEMPERATURE_H);
00091     unsigned char l = read8(REG_TEMPERATURE_L);
00092     return ((h << 8) | l) / 256.0;
00093 }
00094 
00095 #ifdef MBED_OPERATORS
00096 STTS751::operator float() {
00097     return temp();
00098 }
00099 #endif
00100 
00101 char STTS751::read8(char reg) {
00102     _i2c.write(_addr, &reg, 1, true);
00103     _i2c.read(_addr, &reg, 1);
00104     return reg;
00105 }
00106 
00107 void STTS751::write8(char reg, char data) {
00108     char buff[2] = { reg, data };
00109     _i2c.write(_addr, buff, 2);
00110 }