How to connect a Type 'K' Thermocouple to a GTR v1.0

Overview

GTR v1.0 boards should have support for Type ‘K’ thermocouples.
The chip shown below in red, is the MAX31855K ‘K’ type thermocouple support.

GTR MAX31855K Chip
GTR 'K' Thermocouple Chip

Board.txt modifications

The following lines should be added to the board.txt file.

heat.tempSensePins = {C.0, C.1, C.2, C.3}  //regular thermistor pins
//heat.tempSensePins = {A.3, F.9, F.10, F.7, F.5}  //M5 expansion thermistor pins
SPI4.pins = {I.1, I.2, NoPin} //MAX31855K SPI connections SCK, MISO, MOSI
heat.spiTempSensorChannel = 4 //Channel 4 should be free, otherwise try other software SPI
heat.spiTempSensorCSPins = {H.9} //MAX31855K Chip Select

Config.g changes

To use the Type ‘K’ Thermocouple on your hotend, use the following code in config.g

M308 S1 P"H.9" Y"thermocouple-max31855"

Make sure to (re)run the PID-tuning, e.g. M303 T0 S20.

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