AIN bug ?

Testing/Troubleshooting
1

Hi all,

I have a user project that was working correctly until today.

I have several analog sensors each of them are connected on an extra AIN module.

To explain my pb, let’s say the connection diagram is the following :

analog inputs - sensors connected :

AIN 1 - s1

AIN 2 - s2

AIN 3 - s3

AIN 4 - s4

The devices behaves like this :

Sensor 1 works as if it was connected to AIN 1 & 2, sensor 2 is not responding

Sensor 3 works as if it was connected to AIN 3 & 4, sensor 4 is not responding

I believe it’s a multiplexing problem … ? Can this be a hardware failure ?

Thanks for helping …

Olivier

2

Are you using a PIC18F4620 or PIC18F4685? The AIN channel is wrongly selected in the appr. MIOS versions. Since nobody has noticed this before (beside of me), I think that an update is not really urgently required (there are two other changes I want to do for the upcoming MIOS version)

If you are using a PIC18F452, it sounds more like a bug in your hardware?

Best Regards, Thorsten.

3

Hi Olivier,

this sounds very much like the result of one (or more) sensors not connected properly. I discoverd that if you leave one pin unconnected, the signal of the neighboured pins “strays”. This may be not as obvious as it sounds, 'cause the problem may also be the neighbour; esp. if you mix different types of analogue inputs. If it once worked, I’d say a broken or bridged connection sounds most probably.

Maybe something got w(e)ired when you mounted it in the case?

Is only a special type of sensors affected?

If it’s the IR Distance Sensors: I recently distroyed one cause I mixed up + and - and didn’t notice that for some seconds  :-\

Since I found connecting sensors to the AIN sometimes a pain in the arse, I use to solder extra 3-pin connectors on a seperate PCB. These pins allow quick grounding with a jumper or to switch the sensors easily to check for hardware errors:

Regards,

Michael

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4

Thanks both of you.

I’m using the PIC18F452 so it surely comes from my hardware  :wink: thanks Thorsten.

Michael your idea of having the 3 pin PCB is just brilliant ! I’ll think of it for my next box  :smiley: ;D

The pb is with the entire sensors, not only one or two …

I tried to limit number of AIN inputs to 4 (AIN 0 .. 3 are the left pair of joysticks) but the problem still occurs.

I’ll have to investigate deeply tomorrow.

Do you think that if one of the for chips embeded in the AIN would be broken it could possibly lead to such symptoms ?

Laterz specialists  8)

5

It could be an addressing problem like you suggested, either the A0 line is shorted or disconnected, possibly the mux IC’s are no good…

6

I had the chance to find an unused AIN kit and replaced all the ICs of the buggy AIN … nothing changed  :-\ :cry:

I’m seriously dissapointed … but there might be a logical explanation … hope I’ll find …

Perhaps a more understandable explanation about the syndroms :

For two AIN neighbours : if I touch the first one, my applications says nothing (no movement); if I touch the second one, it alternatively sends the values for both as if they were simultaneously touched … + both have always the same value for PinGet()

… and this is true for every pair of AIN pins …

Thanks

Olivier

7

This would happen if selection input A of the multiplexer is either not connected, or if it would have a short against ground or Vss.

Note that this short/open connection/bad solder junction could also be located at the core side

Best Regards, Thorsten.

8

Thorsten, I just seen your message : you were right man, seems like the pb was coming from a bad soldering directly on Vd pin of one of the joysticks …  :wink:

I’m feeling like I was frightened that everything was becoming crazy just at the time I was finishing that damn soldering-marathon (begun 2 years ago)  :stuck_out_tongue: You guess that kinda feeling  ;D :wink:

Thanks all,

Olivier