[REQUEST] Lets make telemetry mod together, step-by-step

[Spoogy]

Oh dear. Another broken board!

Maybe a good idea would be to get a modded main PCB in the post to you?

I have no idea what you are doing wrong. I to date have never killed the main board. These days I have a great jig scope to help with the job - that makes life easy!

Anyway... let me know if you want a modded PCB. Finland is not too far to post one too!

Rob

Sent from my Nexus 7 using Tapatalk 2

Yes indeed...broken. But I'm 100% sure about it's not the fault of what I have done for the board. As you can see from the pics above everything was fine (or do you see something wrong there?). And I can sure you that there was no short anywhere. I'm 100% sure about that. I think that the problem is caused by the usbasp connection but how, that I should have measured.

But now the left button...it is really shorted. Measured from the button pins on the main board. I think I will disconnect it, just to make sure that the button is not mechanically broken.

edit: Okay this is strange. I did NOT disconnected the button from main board. Instead I begin to wonder.... If I now measure from AtMega pin 16 over that SMD resistor it looks good 200 Ohms. And that small hole at next to it, is connected to lowest pins of that left button. And when button is pressed those upper and lower pins are shorted as should be. When button is not pressed those are open. So everything seems to work BUT..

When I put transmitter on and then after a while off and measure between the button upper and lower pins there will be 1,6K Ohms resistance. So, the button is somehow shorted...for awhile... When I measure it couple of times then it will be open again and work perfectly when pressed again (when transmitter is off).

edit2: Yep, the button works mechanically perfect. When the transmitter is on there's varying ohms resistance (from 1K to 5K Ohms) over the button pins all the time. When I press the button it will be shorted (0 Ohms). But because there's that resistance all the time it means the button is newer fully open and that's why transmitter thinks it's pressed. There's good connection between button pins and AtMega pin no. 16 and I cannot see any shorts anywhere. It has to be shorted inside of atmega (once again).

[gohsthb]

Excellent idea Rob!

You cannot check ohms while voltage is applied to a circuit! The resistance readings you get mean nothing when the radio is on. With the radio on you need to use the volts setting of your meter. You should get 0V button pressed or >3V button not pressed. Also after the radio is turned off some capacitors will still have a charge, this is why the pin looks shorted for awhile and then it goes away.
-Gohst

[Spoogy]

Excellent idea Rob!

You cannot check ohms while voltage is applied to a circuit! The resistance readings you get mean nothing when the radio is on. With the radio on you need to use the volts setting of your meter. You should get 0V button pressed or >3V button not pressed. Also after the radio is turned off some capacitors will still have a charge, this is why the pin looks shorted for awhile and then it goes away.
-Gohst

Ah, okay. Good to know. So, the button seems to function perfectly.

But, but.... I did the frsky mod again and connected the usbasp harness and updated er9x frsky version. It warned about the switches and asked to press a key. None of the keys didn't help but the message went away after a while. Then it warned about alarms that they are disabled. That went away also after a while. Finally I was on the main screen. None of the buttons worked so, nothing can be done. Now I will give up. Put that working board back to the transmitter and wait for those AtMegas to arrive (ordered them already). Let's see what happens then....

[Spoogy]

Rob, you got an PM.