Hi, I'm aiming to use an Uno to log 3 channels of temperature data over a long period.
My code currently successfully logs 1 thermocouple hot junction temperature, with a timestamp, and saves it to a .csv file on an SD card. I am using one Adafruit MCP9601 for each thermocouple (3 total) along with the rev B Adafruit data logger shield (ADA1141) for recording to storage, which also has a PCF8523 real-time clock on board. I have come up with my code mainly using the example codes for these products on Adafruit's website.
What I'm struggling to work out is how to get data from all three MCP9601's at once. My aim is to print it to a .csv file like this:
[timestamp 1], channel 1 (°C), channel 2 (°C), channel 3 (°C)
[timestamp 2], channel 1 (°C), channel 2 (°C), channel 3 (°C)
[timestamp 3], channel 1 (°C), channel 2 (°C), channel 3 (°C)
[timestamp 4], channel 1 (°C), channel 2 (°C), channel 3 (°C)
.......etc etc etc
Currently I can log the timestamp and channel 1 but I am unsure of how to get the data from the other MCP9601's at the same time.
I thought that I may be able to use three lines of "mcp.readThermocouple()" from the MCP9601 documentation, with a variation for each different i2c address but I don't think this is possible.
The i2c addresses for my devices are as follows: 0x65, 0x66, 0x67 for the MCP9601's (addr jumpers soldered as applicable) and 0x68 for the RTC.
The period between each logging will be half an hour or longer when the project is complete. I intend to run it from a battery and use some kind of sleep mode in between to save power, but I'll cross that bridge once I've got this working.
I'm learning a lot of this as I go, so any advice or pointers would be very gratefully appreciated.
So if anyone has any suggestions on how I could change this code to log from 3 MCP9601's rather than 1 I'd be very thankful.
My code so far:
#include "Adafruit_MCP9601.h"
#include <SPI.h>
#include <SD.h>
#include <Wire.h>
#include "RTClib.h"
#define ECHO_TO_SERIAL 1 // echo data to serial port
RTC_PCF8523 RTC; // define the Real Time Clock object
// for the data logging shield, we use digital pin 10 for the SD cs line
const int chipSelect = 10;
// the logging file
File logfile;
void error(char *str)
{
Serial.print("error: ");
Serial.println(str);
while(1);
}
void setup(void)
{
Serial.begin(9600);
Serial.println();
// initialize the SD card
Serial.print("Initializing SD card...");
// make sure that the default chip select pin is set to
// output, even if you don't use it:
pinMode(10, OUTPUT);
// see if the card is present and can be initialized:
if (!SD.begin(chipSelect)) {
error("Card failed, or not present");
}
Serial.println("card initialized.");
// create a new file
char filename[] = "LOGGER00.CSV";
for (uint8_t i = 0; i < 100; i++) {
filename[6] = i/10 + '0';
filename[7] = i%10 + '0';
if (! SD.exists(filename)) {
// only open a new file if it doesn't exist
logfile = SD.open(filename, FILE_WRITE);
break; // leave the loop!
}
}
if (! logfile) {
error("couldnt create file");
}
Serial.print("Logging to: ");
Serial.println(filename);
// connect to RTC
Wire.begin();
if (!RTC.begin()) {
logfile.println("RTC failed");
#if ECHO_TO_SERIAL
Serial.println("RTC failed");
#endif //ECHO_TO_SERIAL
}
}
void loop(void)
{
Adafruit_MCP9601 mcp; // define the i2c thermocouple amplifier
DateTime now;
// delay for the amount of time we want between readings
delay(1000);
// fetch the time
now = RTC.now();
// log time
logfile.println((mcp.readThermocouple()));
logfile.print(now.year(), DEC);
logfile.print("/");
logfile.print(now.month(), DEC);
logfile.print("/");
logfile.print(now.day(), DEC);
logfile.print(" ");
logfile.print(now.hour(), DEC);
logfile.print(":");
logfile.print(now.minute(), DEC);
logfile.print(":");
logfile.print(now.second(), DEC);
logfile.print(",");
logfile.print(" ");
logfile.flush();
#if ECHO_TO_SERIAL
Serial.println((mcp.readThermocouple()));
Serial.print(now.year(), DEC);
Serial.print("/");
Serial.print(now.month(), DEC);
Serial.print("/");
Serial.print(now.day(), DEC);
Serial.print(" ");
Serial.print(now.hour(), DEC);
Serial.print(":");
Serial.print(now.minute(), DEC);
Serial.print(":");
Serial.print(now.second(), DEC);
Serial.print(",");
Serial.print(" ");
#endif //ECHO_TO_SERIAL
}
