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App keeps losing connection to the board (glass/magnetic)
#1
Hi there,

Bought a board a couple weeks ago and have really loved it since I've got it setup in our shop.  Until yesterday, when the app kept disconnecting from the board.  I powered down the board and started it back up.  Then, I was able to connect again after two quick disconnects (press, connect, digits turn green then grey very quickly and is disconnected).  Thought it was fixed but walked back after 5-10mins and it was disconnected again.  Kept quick disconnecting until hard restart.

Gave it the night off to think about what it had done and unfortunately it learned nothing and is still quick disconnecting.

I'm at a loss, here.  Is something wrong with my board?

My setup:
Bridgeport Knee Mill, DRO Pros Scales, Quadrature Board,  Samsung Galaxy Tab A 8", 9.5VDC ps

Edit: I've checked to see if it happens to the app on my phone and it does. Random disconnections occur frequently.
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#2
Hm, I've seen this behavior with some tablets running older Android version (4.2-ish) but your Tab A is likely on Android 5 or 6 at least. The reason for this is that when the app looses data it drops the connection, but internally BlueTooth driver still keeps the socket open. When the app re-connects it gets "confused" and keeps disconnecting. I don't see that on my Tab A (it's one of my development/testing tablets), though.
It's possible that there is something happening with the BT module. I havent seen this sort of failure before, though. Most of the deffective ones fail my testing (they are usually dead-on-arrival). In the years that I've been selling the board I had one BT module fail in the filed, but it went completely dead (i.e. the board is not visible to the tablet).
I doubt it's a prblem with the microcontroller. If that was the case, you would not be seeing quick discinnects; those would take 5+ seconds. Another thing I can think of is a cracked/deffective resistor on the BT reset pin. To check if this is the case you can look at the BT status light. When the reset line is pulled down the blinking stops (LED would be off). The resistor is in the upper gight corner, rigt next to the BT module (if the board is held such that "TouchDRO.com" is upright.
In either case, if you keep having this issue please email me. If you're OK with sending the board back I can retest it and repair/replace as needed.
Thank you
Yuriy
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#3
Interesting.. always fun to find a new problem.  Thanks for the quick response!

The tablet is on Android 7.1.1 and my phone is on 9, so I think we can rule that out.

Testing it on the board I get 30.8K ohms on R5. 

Happy to return it, or test anything else if that's not the culprit.

Thanks again!
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#4
Hi both, can you share how you resolved this issue?
I'm seeing something very similar in my  diy build at the base testing stage - Fire tablet is connected OK but the App connects then disconnects after approx 20s. Try to connect again and it disconnects almost immediately. I've tried replacing the BT HC-05 module (same make and model) and behaviour is exactly the same. I've ordered an HC-06 from a different supplier to see if that resolves it. Any other suggestions very welcome!
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#5
Hi both, so the HC-06 module I tried showed the same issue. Tried power cycling the tablet - no change. Tried power cycling the MSP430 - no change. I installed Blue Term, connected to the HC-06 and saw there was no data coming across. Thinking there might be some boot messages at start up I pressed the Reset button - within a few seconds Blue Term showed data coming across and the connection stayed up. Tried connecting the TouchDRO app - system connected and stayed connected.

So my question is - what does the MSP Reset button do that a power cycle of the MSP did not do?
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#6
Blue Term is my new best friend! - whenever this connection problem happens, I use Blue Term and various combination of restart/reset/power cycle until I see the data streaming. At that point I exit Blue Term, restart TouchDRO and all is well - until the next time.
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#7
This is a bit strange. I wonder if there is some sort of brownout when the power cycle happens that causes MSP to fail to start the clock oscillator, so the chip doesn't actually run correctly. I.e. it's possible that when the board powers up the capacitors needs to charge, HC-06 is drawing current, etc. and the Vcc voltage is unstable. When you press reset, the power would be stabilized and the chip starts correctly.
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