How do I update my firmware to be compatible with the RTD Pt100?

How do I update my firmware to be compatible with the RTD Pt100?

The RTD Pt100 works with Marlin, Duet/RepRapFirmware (RRF), and Klipper but requires a MAX31865 amplifier. Many boards have an expansion board for the amplifier like this daughter board by Duet3D


When compiling Marlin, choose temperature sensor #-5. 

Make sure this value is set to -5 if the Pt100 is plugged into the first temperature sensor port.

You will also have to uncomment the following two lines by deleting the two forward slashes. It should look like this.

RRF (Duet)

If you are using RRF, you must edit the M305 or M308 line in your "config.g" file. RRF 2.x or earlier will use the M305 command while RRF 3.x will use the M308 command. The M305 command should look something like this:

M305 P1 X200

The M308 command should look something like this:

For Duet 3:
M308 S1 P"1.spi.cs0" Y"rtd-max31865"

For Duet2:
M308 S1 P"spi.cs1" Y"rtd-max31865"

If the daughterboard is not plugged into the first port or has a CAN bus address of 1, you can change those numbers. You can find more information to better configure your sensor by looking at the documentation provided for the M305 and M308 commands found in the Gcode Dictionary and by looking at Duet's guide for configuring hardware and firmware for the Pt100.


When configuring Klipper, use the following parameters when configuring your "printer.cfg" file. 
sensor_type: "MAX31865"
rtd_nominal_r: 100
rtd_num_of_wires: 2
Check Klipper's documentation for specifics about the amplifier you are using.