swap t0 for t2

Hi, my t0 input on RAMPS appears to be broken, as it reads 50C even without a thermistor plugged in. Could someone tell me how to use t2 in place of t0 for the hotend thermistor? I believe some changes are needed in pins.h in marlin but I have never made changes there before and would rather someone more experienced guided me through it.

Thanks,
Adam

In Pins.h, the three thermistor pins for RAMPS are named TEMP_0_PIN, TEMP_1_PIN and TEMP_BED_PIN, respectively. This is a bit confusing as the board has them labelled as T0, T1 and T2.

TEMP_0_PIN = T0 on board = pin 13.
TEMP_BED_PIN = T1 on board = pin 14.
TEMP_1_PIN = T2 on board = pin 15.

If you change the following line:

#define TEMP_0_PIN 13 // ANALOG NUMBERING

to

#define TEMP_0_PIN 15 // ANALOG NUMBERING

in Pins.h, you should be good to go. This is about line 630 in the file (in the version I have, which is fairly recent).

There's a little guesswork involved in the above, so please test and let us know how you get on.

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Got it, and have it swapped. Now with no thermistor connected i get minitemp and t0 reads 0, which is perfect. I believe i shorted my thermistor through the heater block so now I will have to be more careful to insulate it before powering the heater. Thanks for the help.

A shorted thermistor would read much higher redings, like 800 °C. You choosed the right thermistor table, did you?

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

Traumflug: Only if it's shorted at the time you're looking at it (first time), and even then not as likely because the thermistor tables don't usually go that high.

Once you fry the input on a Mega (which tends to be anything over 5.5V), it tends to internally get locked at a fixed value. I've seen fixed readings through firmware of between 50-150C if the thermistor lead that goes into the Mega analogue input somehow gets connected to the 12V on the hot end (even if through some resistance - as the problem is caused by over-voltage on the analogue input pin of the Mega).