Daniel Blomdahl / MAX31855

MAX31855 library

Fork of MAX31855 by Seeed

MAX31855.cpp@1:d8234681d212, 2016-03-10 (annotated)

Committer:
DanielBlomdahl
Date:
Thu Mar 10 17:58:12 2016 +0000
Revision:
1:d8234681d212
Parent:
0:5d56064bc4c3 
Working code of just one thermocouple (thermometer 1). Only prints data to Terminal. Does not save it to SD card

Who changed what in which revision?

UserRevisionLine numberNew contents of line
yihui 0:5d56064bc4c3 1 /*
yihui 0:5d56064bc4c3 2 * A library for MAX31855
yihui 0:5d56064bc4c3 3 *
yihui 0:5d56064bc4c3 4 * Copyright (c) 2015 Seeed Technology Limited.
yihui 0:5d56064bc4c3 5 * Author : Yihui Xiong
yihui 0:5d56064bc4c3 6 *
yihui 0:5d56064bc4c3 7 * The MIT License (MIT)
yihui 0:5d56064bc4c3 8 *
yihui 0:5d56064bc4c3 9 * Permission is hereby granted, free of charge, to any person obtaining a copy
yihui 0:5d56064bc4c3 10 * of this software and associated documentation files (the "Software"), to deal
yihui 0:5d56064bc4c3 11 * in the Software without restriction, including without limitation the rights
yihui 0:5d56064bc4c3 12 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
yihui 0:5d56064bc4c3 13 * copies of the Software, and to permit persons to whom the Software is
yihui 0:5d56064bc4c3 14 * furnished to do so, subject to the following conditions:
yihui 0:5d56064bc4c3 15 *
yihui 0:5d56064bc4c3 16 * The above copyright notice and this permission notice shall be included in
yihui 0:5d56064bc4c3 17 * all copies or substantial portions of the Software.
yihui 0:5d56064bc4c3 18 *
yihui 0:5d56064bc4c3 19 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
yihui 0:5d56064bc4c3 20 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
yihui 0:5d56064bc4c3 21 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
yihui 0:5d56064bc4c3 22 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
yihui 0:5d56064bc4c3 23 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
yihui 0:5d56064bc4c3 24 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
yihui 0:5d56064bc4c3 25 * THE SOFTWARE.
yihui 0:5d56064bc4c3 26 */
yihui 0:5d56064bc4c3 27
yihui 0:5d56064bc4c3 28
DanielBlomdahl 1:d8234681d212 29 #include "MAX31855.h"
yihui 0:5d56064bc4c3 30
yihui 0:5d56064bc4c3 31 #define LOG(args...) printf(args)
yihui 0:5d56064bc4c3 32
yihui 0:5d56064bc4c3 33 MAX31855::MAX31855(SPI& _spi, PinName _ncs) : spi(_spi), ncs(_ncs)
yihui 0:5d56064bc4c3 34 {
yihui 0:5d56064bc4c3 35 thermocoupleT = 0.0 / 0.0;
yihui 0:5d56064bc4c3 36 internalT = 0.0 / 0.0;
yihui 0:5d56064bc4c3 37 lastReadTime = 0;
yihui 0:5d56064bc4c3 38 }
yihui 0:5d56064bc4c3 39
yihui 0:5d56064bc4c3 40 float MAX31855::read(temperature_type_t type) {
yihui 0:5d56064bc4c3 41 uint8_t buf[4];
yihui 0:5d56064bc4c3 42
yihui 0:5d56064bc4c3 43 uint32_t time = us_ticker_read();
yihui 0:5d56064bc4c3 44 uint32_t duration = time - lastReadTime;
yihui 0:5d56064bc4c3 45 if (duration > 250000) { // more than 250ms
yihui 0:5d56064bc4c3 46 //Set CS low to start transmission (interrupts conversion)
yihui 0:5d56064bc4c3 47 ncs = 0;
yihui 0:5d56064bc4c3 48
yihui 0:5d56064bc4c3 49 //Read in Probe tempeature
yihui 0:5d56064bc4c3 50 for (int i = 0; i < 4; i++) {
yihui 0:5d56064bc4c3 51 buf[i] = spi.write(0);
yihui 0:5d56064bc4c3 52 }
yihui 0:5d56064bc4c3 53
yihui 0:5d56064bc4c3 54 //Set CS high to stop transmission (restarts conversion)
yihui 0:5d56064bc4c3 55 ncs = 1;
yihui 0:5d56064bc4c3 56
yihui 0:5d56064bc4c3 57 if (buf[1] & 1) {
yihui 0:5d56064bc4c3 58 uint8_t fault = buf[3] & 0x7;
yihui 0:5d56064bc4c3 59 if (fault & 0x1) {
yihui 0:5d56064bc4c3 60 LOG("The thermocouple is open (no connections).\r\n");
yihui 0:5d56064bc4c3 61 }
yihui 0:5d56064bc4c3 62 if (fault & 0x2) {
yihui 0:5d56064bc4c3 63 LOG("The thermocouple is short-circuited to GND.\r\n");
yihui 0:5d56064bc4c3 64 }
yihui 0:5d56064bc4c3 65 if (fault & 0x4) {
yihui 0:5d56064bc4c3 66 LOG("The thermocouple is short-circuited to VCC.\r\n");
yihui 0:5d56064bc4c3 67 }
yihui 0:5d56064bc4c3 68 return 0.0 / 0.0;
yihui 0:5d56064bc4c3 69 }
yihui 0:5d56064bc4c3 70
yihui 0:5d56064bc4c3 71 int t1 = ((buf[0] & 0x7F) << 6) + (buf[1] >> 2);
yihui 0:5d56064bc4c3 72 if (buf[0] & 0x80) { // sign bit
yihui 0:5d56064bc4c3 73 t1 = -t1;
yihui 0:5d56064bc4c3 74 }
yihui 0:5d56064bc4c3 75 thermocoupleT = t1 * 0.25;
yihui 0:5d56064bc4c3 76
yihui 0:5d56064bc4c3 77 int t2 = ((buf[2] & 0x7F) << 4) + (buf[3] >> 4);
yihui 0:5d56064bc4c3 78 if (buf[2] & 0x80) {
yihui 0:5d56064bc4c3 79 t2 = -t2;
yihui 0:5d56064bc4c3 80 }
yihui 0:5d56064bc4c3 81 internalT = t2 * 0.0625;
yihui 0:5d56064bc4c3 82 }
yihui 0:5d56064bc4c3 83
yihui 0:5d56064bc4c3 84 if (THERMOCOUPLE_T == type) {
yihui 0:5d56064bc4c3 85 return thermocoupleT;
yihui 0:5d56064bc4c3 86 } else {
yihui 0:5d56064bc4c3 87 return internalT;
yihui 0:5d56064bc4c3 88 }
yihui 0:5d56064bc4c3 89 }
yihui 0:5d56064bc4c3 90
yihui 0:5d56064bc4c3 91