Nano V2 - Dead Input?

I received my Nano V2 a few weeks ago. I put BenF 3.40 on it and watched the signal generator output for a moment, then put it away. I haven’t needed it for anything since then, but I thought I’d show it off to the folks at work. So, I upgraded to 3.51. Sadly, I can’t see an active signal now. Only a flat line at 0V (no noise when disconnected, either). I checked the signal generator output on another scope and it works fine. I downgraded to 3.41 and it appears that the input always reads a max value or something – V Avg = Vmin = Vmax = 6.84 or something on 1v/div (I can downgrade and get the exact number, if it matters). Seems like a HW problem, unless there are stored cfg files messing things up? I assume that it reads zero on 3.51 because the ground calibration get’s set to max. How can I diagnose it?

I sent this to the support email, too, but thought:
a) might get quick help here
b) someone else may run into this someday…


I’ve attached a configuration profile (FILE004.CFG within zip file) that sets all parameters to some reasonable value. Can you extract this file, load it on your Nano using V3.51 and see if it makes a difference? This would help eliminate the possibility that some invalid settings cause this. You will need a micro SD card and copy the configuration file to a sub directory named PROFILE. Then use menu option FI and sub option Load Pro to locate and load the FILE0004.CFG file from the SD card. (224 Bytes)

Thanks for the help. I loaded the profile per your suggestion, but sadly, I still see a flat line, even with no input (i.e. no noise wiggling the line). I also (at the suggestion of the tech support) loaded the original 2.40 app, and it shows DC V=6.04 with no input. Depending on what tech support suggests, I could open it up and take a measurement at, say, “Ain” or something; not sure what the ‘correct’ value would be with no input…

I haven’t looked at the schematic in too much detail, but I didn’t notice any transient suppression devices (i.e. to combat static); maybe something got zapped? Or, maybe that’s not an issue with a self-contained portable device? Notice I keep blaming the hardware? I’m a software guy :smiley:

Thanks again!

Your first post made a lot of sense in the way you approached this and how you interpret the results. It sure looks like a HW issue, but it is always good to rule out other possibilities.

If you’re handy with electronics, you might want to have a go at fault finding yourself. Tracing the input from the connector and back to the analog input on the microcontroller would be a good start. It could be as simple as an issue with the connector coming loose from the circuit board, but it could also be a component failure of some sort.

If it is just a few weeks old and you have hardly used it yet I don’t think seeedstudio have any problems exchanging it. I got the impression that they have been very service minded so far which is appreciated. They just might be slowing down a bit now until 6 feb, chinese spring festival.
Don’t waste a lots of time on this (if you don’t want to of course :wink:

I probed some voltages, and it would seem that the issue is that the +5 v supply is now at -1.4v. I’ll wait to hear from tech support before proceeding. Thanks to all!

So, Seeed did offer to fix it for me, but due to the Lunar New Year delays in communication, and the anticipated delay in sending it to China and back, I opted to fix it. I traced it back to U7, the TC1240 Charge Pump. Ordered one from DigiKey and popped it in, and all is well! The calibration is off, but that was also easily remedied…