Hello,
the board has a wrong layout on one position.
Look at the the "2,3,4" PINS above the REF resistor (which can be solderd).
As you can see PIN 2 (the left PIN) is connected to ground, PIN3 (the right PIN) is connected to FORCE+ of the max31865 and PIN4 (the middle PIN) is connected to FORCE2 of the max31865.
If you look at the datasheet of the MAX31865 at page 8 in the "PIN DESCRIPTION" Table you will see under NAME the FORCE2 (goes to PIN4 note:
Positive Input Used in 3-Wire Only. When in the 3-wire connection configuration, connect to FORCE+ (goes to PIN3). When in the 2-wire or 4-wire connection configuration, connect to ground.
The problem is that PIN4 is per layout shorted to PIN2 and therefore if you solder 3 and 4 the FORCE2 PIN is grounded. Soldering PIN2 and PIN4 is useless.
To make it work you have to cut the small purple line between PIN2 and PIN4. Maybe scretch it away with a small screw-driver. See the attached Picture.
Then solder PIN3 and PIN4 for 3-Wire configuration.
Dont forget to solder the 2/3Wire labled PINS.
If you want to use 2-Wire solder 2/3 labled PINs, solder 2Wire labled PINS and solder 2,4 PINS near the REF Resistor.
If you want to use 4-Wire solder only solder 2,4 PINS near the REF Resistor.
Check with your multimeter if PIN2 and PIN4 realy disconnected (with beep mode).
Greets
EDVler
