MAX6675_RK (community library)

Summary

Name	Value
Name	MAX6675_RK
Version	0.0.2
Installs
License	MIT
Author	rickkas7
URL	https://github.com/rickkas7/MAX6675_RK
Repository	https://github.com/rickkas7/MAX6675_RK.git
Download	.tar.gz
All Versions	0.0.2, 0.0.1

MAX6675 SPI thermocouple library for Particle devices

Example Build Testing

Device OS Version:

This table is generated from an automated build. Success only indicates that the code compiled successfully.

Library Read Me

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MAX6675_RK

MAX6675 SPI thermocouple library for Particle devices

Repository: https://github.com/rickkas7/MAX6675_RK
License: MIT
Full browseable API documentation: https://rickkas7.github.io/MAX6675_RK/index.html

API

Allocate an object

You will typically allocate one of these objects as a global variable.

// Examples. Select only one!
MAX6675_RK sensor;
// MAX6675_RK sensor(A0);
// MAX6675_RK sensor(&SPI1, D5);

You can configure more than one sensor by creating multiple objects. Each sensor must have its own CS line. See example 2-multiple.

Initialize the object in setup()

void setup() {
sensor.setup();
}

Read the value

Use the readValue() method to read the value in degrees Celsius:

float value = sensor.readValue();
if (!std::isnan(value)) {
Log.info("value=%f", value);
}

Example

I purchased this set of inexpensive MAX6675 with thermocouples from Amazon. There are many similar boards available on Amazon, eBay, and AliExpress.

Pin	Description	Connects To	Picture
GND	Ground	GND	Gray to GND
VCC	3.0 to 5V	3V3	Purple to 3V3
SCK	SCK	SCK	Blue to SCK
CS	Chip Select	Available GPIO	Green to S3
SO	Data Out	MISO	Yellow to MISO

The CS pin can be connected to any available GPIO. There is a default CS pin named SS that varies depending on the device, but you don't have to specifically use that pin.

The color doesn't matter, and that is not the same Dupont wire that came with the thermocouple adapter as I wanted male-to-female instead of female-to-female. The colors are only listed to clarify the picture.

Wiring (image removed)

The connections on this adapter board:

Board connections (image removed)

The sample code in examples/1-Simple can be used to test the firmware side.

The output should look like this:

0000022622 [app] INFO: value=26.500000
0000024622 [app] INFO: value=26.750000
0000026622 [app] INFO: value=26.500000
0000028622 [app] INFO: value=26.500000
0000030622 [app] INFO: value=26.500000
0000032622 [app] INFO: value=26.250000
0000034622 [app] INFO: value=26.500000
0000036622 [app] INFO: value=26.500000
0000038622 [app] INFO: value=26.750000

If you disconnect the T+ or T- thermocouple connection, you should see something like:

0001088622 [app] INFO: value=26.500000
0001090622 [app] INFO: sensor not available
0001092622 [app] INFO: sensor not available
0001094622 [app] INFO: value=26.500000

If you disconnect the SPI interface, you will typically get a value of 0.

MAX6675

From the datasheet:

Cold-Junction-Compensated K-Thermocouple-to-Digital Converter (0°C to +1024°C)

The MAX6675 performs cold-junction compensation and digitizes the signal from a type-K thermocouple. The data is output in a 12-bit resolution, SPI-compatible, read-only format.

This converter resolves temperatures to 0.25°C, allows readings as high as +1024°C, and exhibits thermocouple accuracy of 8 LSBs for temperatures ranging from 0°C to +700°C.

The MAX6675 is available in a small, 8-pin SO package.

Direct Digital Conversion of Type -K Thermocouple Output
Cold-Junction Compensation
Simple SPI-Compatible Serial Interface
12-Bit, 0.25°C Resolution
Open Thermocouple Detection

Additionally:

Unidirectional 3-wire SPI interface (SCK, CS, and SO only)
3.0 to 5.5V recommended supply voltage
Serial clock frequency maximum: 4.3 MHz
SPI Mode 3 (CPOL=1, CPHA=1) (data sampled on the second edge, idle high)

SPI timing (image removed)

Version History

0.0.2 (2025-12-11)

Added example for multiple sensors (2-multiple)

0.0.1 (2025-12-10)

Initial version