I was so unlucky to not notice a short circuit between the hotend resistor and the thermistor, before three of my thermistor connections were destroyed (the full VBB gets into the 3.3V based ADC input). Stupid, yes, but in order to be able to measure the temperature of the heated bed I need another ADC. It seems that the spare connector 1.30 (and 1.31) is actually registered as ADC in mbed. How can I configure/change the firmware such that this is seen as ADC by smoothieware and can be used as temperature measurement?
So in the firmware/config, you just do it the same way you did before, no change there.
However, that input does not have the passives ( resistor and capacitor ) the other inputs have, so you’ll probably need to add those yourself ( outside the board ).
Do you mean that I can replace the original ‘0.23’ (for the hot end) with ‘1.30’ and add the 4.7kOhm resistor and the 10uF Capacitor and I am just fine?
I have tried that but it did not seem to work. It seemed to me that ‘1.30’ is configured as a digital output. I connected a potentiometer and got constant readings for all resistances and when the resistance approached 0 the board crashed (no damage, I think)
Do you mean that I can replace the original ‘0.23’ (for the hot end) with ‘1.30’ and add the 4.7kOhm resistor and the 10uF Capacitor and I am just fine?
Exactly.
I have tried that but it did not seem to work. It seemed to me that ‘1.30’ is configured as a digital output. I connected a potentiometer and got constant readings for all resistances and when the resistance approached 0 the board crashed (no damage, I think)
I think that means it is wired wrong in some way. Can you make sure you are doing it exactly like on Smoothieboard ?
Thank you for the answer. Having a closer look on the board and my connection trial I see that I probably misunderstood and used the wrong connection pad. Since JP30 and JP31 exit, I thought that these would be the right pads for AD0[4] and AD0[5]. I found the JP30 and JP31 on the Smoothieboard schematics and these have nothing to do with ADC and P1.30/P1.31.
Therefore: where on the Smoothieboard do I find the correct pad or hole for the spare connectors P1.30 and P1.31?
Regards
P.s. Working with the pins I found a little error in the Smoothieboard_LPC1769 Pin Usage table: I thing P1.30 is connected to Pin 21, not Pin 19 as listed.
the pins you’re looking for are next to the ethernet jack.
I checked the smoothieboard eagle files and P1.30 is connected to Pin 21, AD0[4] and P1.31 is connected to Pin 20, AD0[5].
Edit: I’m actually not sure if the (lpc1769-pin-usage) column LPCXpresso Pin means the actual pin number on the chip or if its just some kind of mapping like the Mbed Pin or Arm Pin mappings. Can anybody clarifies this?