TL;DR: Endstops aren't working. Power pins are receiving +5V and GND. Sense pins don't read any change when GND and sense are bridged on RAMPS board, however, if I bridge the corresponding sense pins to GND on the bare Arduino (without RAMPS installed) M119 give expected output. Can I fix this stupid board?
I'm using RAMPS 1.4 + Mega2560 + 4ct Pololus. All are knockoffs.
Currently I have:
- Endstop inverting DISABLED.
- Max endstops DISABLED.
- Endstop Pullups ENABLED.
As I understand it, in the configuration, an open circuit on the endstop should give me an "triggered" result from M119; when the sense pin is pulled to GND it should give me an "open" result from M119.
The problem is: No matter what I do or what pins are bridged, M119 always returns "triggered" for all endstops.
All endstop pins are misbehaving in the same way but I'm focusing my troubleshooting efforts on the sense pin going to #18 on the Arduino -- the z endstop pin.
This is what I've been able to observe so far with my multimeter:
- The + pin receives 5V relative to GND on the Arduino (it appears to be working correctly).
- The - pin receives -5V relative to 5V on the Arduino (it appears to be working correctly).
- There is continuity between the sense pin on top of the board and the pin that enters the Arduino at #18.
- The voltage between the sense pin and GND appear to float by about .25v +/- (this happens on the bare Arduino, too, I'm guessing that it doesn't really matter).
- Last, and most important:
if I bridge the sense pin on the RAMPS board to ground WITHOUT the RAMPS board installed M119 reports the correct result!
At this point I'm thinking that the RAMPS board is hosed; I'm approaching the end of my (limited) electronics troubleshooting skills and I would certainly appreciate any insights on how to get this thing working.
Edited 1 time(s). Last edit at 04/21/2014 11:23AM by jnovek.
