About

This library has been written to support the Maxim MAX11210 24-bit A/D converter as peripheral of the Spark module. Spark libraries can be used in the Spark IDE .

Example Usage

The code snippet below shows how to add the high resolution A/D converter to the example for measuring the temperature.

#include "maxim-max11210.h"

int sensor1 = 0;
double temperature1 = 0.0;
double sensor2 = 0;
double temperature2 = 0.0;

// Declare the peripheral A/D converter as type Max11210 from the Maxim namespace
Maxim::Max11210 adcMax11210;

void setup() {
  Spark.variable("Temp1", &temperature1, DOUBLE);
  Spark.variable("Temp2", &temperature2, DOUBLE);
  pinMode(A7, INPUT);
  adcMax11210.begin();
}

void loop() {
  sensor1 = analogRead(A7);
  sensor2 = adcMax11210.read();
  
  // TMP36: 0.5 V offset voltage, 10 mV/degC, 750 mV at 25 degC
  // 12-bit A/D for sensor 1: (2^12 - 1) = 4095 steps
  // 24-bit A/D for sensor 2: (2^24 - 1) = 1677215 steps 
  temperature1 = (3.3 * sensor1 / 4095.0 - 0.5) * 100.0;
  temperature2 = (3.3 * sensor2 / 16777215.0 - 0.5) * 100.0;
}

In a second example the configuration settings of the MAX11210 are changed by sending commands through a function of the Spark module.

#include "maxim-max11210.h"

double sensor2 = 0;
double temperature2 = 0.0;

// Declare the peripheral A/D converter as type Max11210 from the Maxim namespace
Maxim::Max11210 adcMax11210;

void setup() {
  Spark.variable("Temp2", &temperature2, DOUBLE);
  Spark.function("Command", cmdFunction);
  adcMax11210.begin();
}

void loop() {
  sensor2 = adcMax11210.read();
  temperature2 = (3.3 * sensor2 / 16777215.0 - 0.5) * 100.0;
}

int cmdFunction(String command) {
  if (command == "SELFCAL") {
    adcMax11210.setDisableSelfCalGain(false);
    adcMax11210.setDisableSelfCalOffset(false);
    adcMax11210.selfCal();
    selfcalgain = adcMax11210.getSelfCalGain();
    selfcaloffset = adcMax11210.getSelfCalOffset();
    return 1;
  }
  if (command == "SYSCALOFFSET") {
    // System level calibration should only be performed when a zero-scale signal can be presented to the ADC.
    // Give a rate command afterwards to reinitiate conversion.
    adcMax11210.setDisableSysOffset(false);
    adcMax11210.sysOffsetCal();
    syscaloffset = adcMax11210.getSysOffsetCal();
    return 1;
  }
  if (command == "SYSCALGAIN") {
    // System level calibration should only be performed when a full-scale signal can be presented to the ADC.
    // Give a rate command afterwards to reinitiate conversion.
    adcMax11210.setDisableSysGain(false);
    adcMax11210.sysGainCal();
    syscalgain = adcMax11210.getSysGainCal();
    return 1;
  }
  if (command == "RATE1") {
    adcMax11210.setRate(MAX11210_RATE1);
    return 1;
  }
  if (command == "RATE2_5") {
    adcMax11210.setRate(MAX11210_RATE2_5);
    return 1;
  }
  if (command == "GAIN1") {
    adcMax11210.setGain(MAX11210_GAIN1);
    return 1;
  }
  if (command == "GAIN2") {
    adcMax11210.setGain(MAX11210_GAIN2);
    return 1;
  }
  // Simply add other commands here ...
  return -1;
}

Both examples can be found in the example project dual-tmp36.ino provided with this library.

Circuit Diagram

See the breadboard view below as an example of combining the Spark module with the ADC and a temperature sensor.

Recommended Components

Maxim MAX11210

Analog Devices TMP36

Adafruit TSSOP-16 breakout PCB

Status

Debugging is ongoing. After manually performing a full system calibration according to the procedure in the data sheet, valid temperature measurements are provided. Manually apply 0.0 V to the AINP-pin during system offset calibration. Apply 3.3 V to the AINP-pin during the system gain calibration. This gives me the following data in the calibration registers:

SCG  = 0xBFE318
SCO  = 0xFFFF74
SCGC = 0x7FFF6C
SCOC = 0xFFF4E9

A work-around has been implemented for the SPI safety in the firmware of the Spark Core, which prevents reading the MISO to detect completion of a conversion. Note the wires connecting !RDY/DOUT to both MISO and D0 of the Spark Core.