MAX31855.cpp

/* =====================================================================
   Copyright © 2016, Avnet (R)

   www.avnet.com 
 
   Licensed under the Apache License, Version 2.0 (the "License"); 
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, 
   software distributed under the License is distributed on an 
   "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, 
   either express or implied. See the License for the specific 
   language governing permissions and limitations under the License.

    @file          MAX31855.cpp
    @version       1.0
    @date          Sept 2017

======================================================================== */


#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include "iot_monitor.h"

#include "MAX31855.hpp"

MAX31855::MAX31855() { 
    spi_bus_t    bus  = SPI_BUS_II;
    spi_bpw_t    bits = SPI_BPW_32;
    spi_mode_t   mode = SPIMODE_CPOL_0_CPHA_1;
    uint32_t     freq = 960000;
    int i;

    myspi = 0;
    i=spi_bus_init(bus, &myspi);
    if( i<0 )
        printf("ERROR:spi_format()=%d\n",i);

    i=spi_format(myspi, mode, bits);
    if( i<0 )
        printf("ERROR:spi_format()=%d\n",i);

    i=spi_frequency(myspi, freq);
    if( i<0 )
        printf("ERROR:spi_frequency()=%d\n",i);
}

MAX31855::~MAX31855(void) {
    spi_bus_deinit(&myspi);
}

uint32_t MAX31855::readSPI(void) 
{
    uint32_t rxb, txb;

    rxb = txb = -1;
    errs = 0;
    if( spi_transfer(myspi, (uint8_t*)&txb, sizeof(uint32_t), (uint8_t*)&rxb, sizeof(uint32_t))<0)
        errs = 0x08;

    return rxb;
}

//
// returns 0 if no errors, otherwise !0
//
//     1011 0110 1111 1100 1011 0111 0001 0100
//                      || |||| |||| |||| ||||+OC Fault  (Open Circuit)
//                      || |||| |||| |||| |||+ SCG Fault (Short to GND)
//                      || |||| |||| |||| ||+  SCV Fault (Short to Vcc)
//                      || |||| |||| |||| +    RESERVED
//                      || ++++ ++++ ++++      12-bit Internal Temperature
//                      || +                   SIGN
//                      |+                     Fault when any of the SCV, SCG, or OC faults are active
//                      +                      RESERVED
//     ++++ ++++ ++++ ++                       14-bit Thermocouple Temp Data
//     +                                       SIGN
//
int MAX31855::read31855(void) {
    uint32_t  rxval = readSPI();
    
    thermo_temp = ((int32_t)rxval & 0xfffc0000)>>18;  //14-bit temp
    intern_temp = ((int32_t)rxval<<16)>>20;           //12-bit temp
    
    errs = rxval & 0x7;

    if( DBG_SPI & dbg_flag ) {
        printf("SPI: read       = 0x%08X\nSPI: thermo_temp= %d\nSPI: intern_temp= %d\nSPI: errs   =0x%02X\n", 
                rxval, thermo_temp,intern_temp,errs);
        }

    return -errs;
}


double MAX31855::readThermo(int InCelcius) {
    double v;

    if( read31855() <0 ) 
        return 0;
    v = thermo_temp * 0.25;
    if( !InCelcius ) 
        v = (v*9.0)/5.0 + 32;
    return v;
}


double MAX31855::readIntern(int InCelcius) {
    double v;

    if( read31855() <0 )
        return 0;
    v = intern_temp * 0.0625;
    if( !InCelcius ) 
        v = (v*9.0)/5.0 + 32;
    return v;
}
        

uint8_t MAX31855::readError() {
  return errs;
}


int MAX31855::loopbackTest()
{
    int i;
    uint32_t     rxb=0, txb=0x01234567;

    errs = 0;
    if( spi_transfer(myspi, (uint8_t*)&txb, sizeof(uint32_t), (uint8_t*)&rxb, sizeof(uint32_t))<0)
        errs = 0x08;

    if( DBG_SPI & dbg_flag ) 
        printf("SPI LBT: rxb = 0x%08X, txb=0x%08X, errs =0x%02X\n", rxb, txb, errs);
    return (rxb == txb);
}