Hard reset (pulling pin44 to ground) not working
The reset switch on the board (Duet 2 Ethernet) works ok, but nothing happens when I ground pin 44.
Reading approx. 3.1 volt on pin 44 when floating. Per board diagram, this is normal.
Looking at the diagram, R107 should be a 100ohm resistor and I guess it is there as a level of protection when grounding the pin.
Problem is I measure 10K on R107 (same as R106 which is normal).
So , this looks to me like an assembly error...
Has anyone else come across this ?
We became aware in July 2018 that a batch of Duet 1.04 boards was manufactured with the wrong value resistor at R107. This was corrected in manufacturing the following day. I will add a note about tis to the wiki page about PCB revisions.
The easiest way to correct your board would be to solder a 100R resistor on top of the existing one. This would avoid having to remove the existing resistor, which is difficult to do without either heated tweezers or hot air rework equipment.
I'm sorry for the inconvenience this has caused you.
The only SMD I have on hand is 51ohms and I was thinking of installing it: I have done a bit of SMD 'manual' work before, but is there something special with the board that would make it more difficult to remove? I have a Hanko soldering station with a number of different tips I can use. What would be the best temperature to select for removal ?
Is there enough material on the tips of such SMDs to make it possible to solder one on top of the other ?
I do have plenty of 100ohms radial resistors , if it turns out to be the best solution.
51 ohms is OK. The resistor serves to limit the initial discharge current of the reset capacitor when you short that pin to ground.
SMD resistors invariably have metal endcaps, which makes it easy to solder one on top of another. Removing SMD resistors without damaging the PCB traces requires heating both pads at the same time, which is difficult to do if all you have is a soldering iron.
I think I will go with the simple route: just solder on top...