When I execute the Repstrap-commtest.py result is a temperature of 0 °C but this temperature is impossible. Why I obtein this result?

Maybe because 0 value is the initial value of the variable that holds temperature, on the firmware.

You have for sure a connection problem on the thermistor or something else.

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I've got the exact same problem. Did you ever solve it?

Update having added Serial.start(19200); to the setup() function of the extruder boards program Extruder.pde in the arduino environment.

I added to extruder_class extruder::internalTemperature right before return(celsius) :

Serial.println(celcius);


This reads the temperature so I will trace it ferther...

Ok the reprap host software reads the temperature, but not regularly.
The temperature value only updates when the "Switch heat on button is pressed.
It doesn't update after that unless this button is pushed again.

Apparently the Ramp button is ineffective.
I guess these are all host software bugs.

thanks