MESA 7i76U inputs changing state without changes to config

Thanks for responding Tommy.

As I mentioned the 24v power supply is holding steady at 24.1v. I've had my DVM connected for several hours without a single deviation, so I'm confident the PS is good. I've just sent the results of my findings to MESA tech support to get their input on the issues.

scsmith1451 wrote:

As I mentioned the 24v power supply is holding steady at 24.1v. I've had my DVM connected for several hours without a single deviation, so I'm confident the PS is good.

I am glad you are confident, but DVM will not show ripple and high frequency mess that supply is causing, scope does, and does require using AC and DC coupling for all the checks.
You can try adding a capacitor in parallel to power output and check LinuxCNC if it stabilizes at all, but if the power supply has no inductor filtering on the output still might not be enough.
Sorry for insisting on this, but all china power supplies are getting utterly useless, been dealing with those daily for the last 17 years and seen terrible implementations to the point where the output inductor would burn to a crisp after 2-3 hours of being on with 10-50% of rated load. These were made by Horoz and all failed the same, by the hundreds.

Well, tested the card and found no issues.

All inputs read low at 50% of field voltage and high at 65% of field voltage
applied to an input.

Heated to +70C and cooled to -40C and still no issues. Ran at 5V to 32V field
voltage and no issues.

Here is an image of all disconnected inputs in halshow (@ 24V)

 

 

I'm just tuning in to this discussion, so maybe I missed this, but: On my Mesa 7i96 the Mesa inputs aren't like most digital inputs. They're not self-referenced. They all share a "common" pin, which should be grounded if the inputs are active high, or pulled high if the inputs are active low. Is it possible your 7i76 inputs are the same? Have you done that? If you don't, the your input might not be floating, but its reference is, and could easily lead to erratic/intermittent behavior.

paul

First off, my apologies for not responding earlier, I've been waiting for my 7i76u to be returned before moving forward plus chores around the homestead have been a hinderance for time.

As Peter said the board was tested and found within specs. Out of an abundance of caution, I ordered as 24 v laptop PS which I received it this morning. After putting it on my scope and monitoring it for several minutes I found only glitches of < .1 v while holding an output voltage of 24.5 v which was the same with the previous PS only at 24.1 v.

Next I reinstalled the MESA board and mapped the X,Y and Z limits to inputs 0,1,2 and the probe to input 4 with EStop on 5. Restarting LCNC with sserial set to 20xxxxxx I monitored the fldvoltage and the four analog inputs. 0,1,2 (the limit switches) reflected the fldvoltage at all times. The probe voltage (input 04) fluctuated wildly between 0-3 v until I grounded the probe plate at which time it matched the other three inputs.

Next step was to reset sserial back to 00xxxxxx and restart LCNC. None of
first four inputs responded as expected.

After shutting down and powering off the machine I remapped X/Y/Z limits, Probe and EStop inputs to inputs 04-08 respectively. After power up and restarting LCNC the Limits and EStop responded as expected, however the Probe on input 07 did not. LCNC sees it as triggered on startup and going low upon contact. OK, shutting down LCNC and changing the HAL file to invert input 07 then restarting pin 07 still responds the same, i.e. high on startup and going low when contact is made.

My next step will be to rewire all of the inputs as sourcing inputs by moving the power legs from the +24v buss to the GND buss, change HAL to reflect the changes and retest.

Taking a break for a couple of hours then I'll let you know of my progress.

Well, that didn't work. Inputs are back to sinking inputs as specified in the manual. I did comment out the PROBE input so it is not currently part of the configuration. However, on startup LCNC continues to show the EStop button activated so I cannot continue testing Homing.

Unable to continue at testing at this point.

These are the states of the inputs at this time:

 

And this is my HAL config:

 

Any help would be greatly appreciated.