GroveStreams Electric Imp Device

// Electric Imp Device Code for GroveStreams Example
// A full "how to" guide for this agent can be found at https://www.grovestreams.com/developers/getting_started_elec_imp_temp.html
//

// License:
//  Copyright 2014 GroveStreams LLC.
//  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.

// Read data from MAX31855 chip on Adafruit breakout boards
// Code developed by Electric Imp Forum members rivers,
// mjkuwp94, Brown, as well as Hugo, peter, and others.
// Modified for use by Mike Mills.
//      pins:
//      imp 1 CLK
//      imp 2 CS
//      imp 5 UNASSIGNED
//      imp 7 UNASSIGNED
//      imp 8 UNASSIGNED
//      imp 9 DO

//Configure Pins
hardware.spi189.configure(MSB_FIRST | CLOCK_IDLE_LOW , 1000);
hardware.pin2.configure(DIGITAL_OUT); //chip select

// define variables
temp32 <- 0;
farenheit <- 0;
celcius <- 0;

//Define functions
function readChip189(){
        //Get SPI data
    hardware.pin2.write(0); //pull CS low to start the transmission of temp data
      //0[31..24],1[23..16],2[15..8],3[7..0]
        temp32=hardware.spi189.readblob(4);//SPI read is totally completed here
    hardware.pin2.write(1); // pull CS high
        // Begin converting Binary data for chip 1
    local tc = 0;
    if ((temp32[1] & 1) ==1){
        //Error bit is set
        local errorcode = (temp32[3] & 7);// 7 is B00000111
        local TCErrCount = 0;
        if (errorcode>0){
            //One or more of the three error bits is set
            //B00000001 open circuit
            //B00000010 short to ground
            //B00000100 short to VCC
            switch (errorcode){
            case 1:
                server.log("TC open circuit");
                break;
            case 2:
                server.log("TC short to ground");
                break;
            case 3:
                server.log("TC open circuit and short to ground")
                break;
            case 4:
                server.log("TC short to VCC");
                break;
            default:
                //Bad coding error if you get here
                break;
            }
            TCErrCount+=1;
            //if there is a fault return this number, or another number of your choice
             tc= 67108864;
        }
        else
        {
             server.log("error in SPI read");
        }
    }
    else //No Error code raised
    {
        local highbyte =(temp32[0]<<6); //move 8 bits to the left 6 places
        local lowbyte = (temp32[1]>>2); //move to the right two places
        tc = highbyte | lowbyte; //now have right-justifed 14 bits but the 14th digit is the sign
        //Shifting the bits to make sure negative numbers are handled
        //Get the sign indicator into position 31 of the signed 32-bit integer
        //Then, scale the number back down, the right-shift operator of squirrel/impOS
        tc = ((tc<<18)>>18);
        // Convert to Celcius
            celcius = (1.0* tc/4.0);
        // Convert to Farenheit
        farenheit = (((celcius*9)/5)+32);
        server.log(celcius + "°C");
        server.log(farenheit + "°F");

        //Gather and pass the data to the Electric Imp Agent running in the cloud
        local data = { id = hardware.getimpeeid(), mac = imp.getmacaddress(), temp = farenheit, voltage = hardware.voltage()}
        agent.send("GroveStreams", data);

        imp.wakeup(20, readChip189); //Wakeup every 20 second and read data. Change this value to change your sample frequency.
    }
}


//Begin executing program
hardware.pin2.write(1); //Set the Chip Select pin to HIGH prior to SPI read
readChip189();          //Read SPI data