PCB issue causing the nano to freeze

I have issue with my pcb, when I connect the nano it stops responding, nothing coming on serial port and the TX led is not blinking.

When I connect the nano and the ADS1115 without the PCB all is working fine. So I guess the nano and the ADS are fine.

I’ve tried to connect the nano to the PCB one pin at a time to find the culprit. So, nano connected to USB, I plugged GND (nano still ok), plugged 5V (still ok), plugged SCL (still ok), plugged SDA and arduino stopped working instantly, unplugged SDA and works again. So, the culprit seems to be the SDA circuit.
Here is some picture of my PCB, nothing seems wrong on my opinion.


So, I did some measurement on the PCB with and without the arduino:
The tension between the GND and HIGH pin of the WAS sensor is curious, is it normal?

Also note that I’m using the KaupoiMOD PCB v2.0 - #8 by Kaupoi which is the same design of the PCB v2 on a smaller size.

Now, I don’t know what to test and how… I just don’t want to unsolder all the components because it will be very difficult.

Try removing the nano and ads1115 and measure the voltage at the power supply pins of nano. Make sure power isn’t where it shouldn’t be. With power off, use an ohmmeter and check there isn;t a short between pins, use a brush and clean the solder blobs off as best you can. Try putting in just the nano, and see if that works as well.

It’s tough :frowning: and frustrating.

If I plug the nano and the ads with wire to the pcb it works until I plug SDA. If i connect everything except SDA and SCL that I connect with direct wire between nano and ads, it works!

Then I measured the resistance between SDA and SCL on the PCB without connecting the nano and ads, it’s around 30Kohms. It seems abnormal to me but what does it mean?

There may be short circuit between ADS1115’s header pin 4 and 5. Pin 5 is GND.


Is this a short to ground?

there is no short between SDA et GND, it seems to be a short between SDA and SCL. Jean-Marc tested his PCB and between SDA and SCL => 0 ohms. I don’t see anything wrong so I guess it’s in the internal circuit…

I will try unsoldering everything and move to another pcb.

There is no internal circuit on the PCB?

@Gg1212, there must be a little piece of solder or something shorting them together. You are so close! Don;t give up just yet!

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I have unsoldered everything from the PCB and then there was infinite resistance between SDA and SCL, so no more short. The conclusion is that indeed there was probably a piece of solder or something shorting the circuits! I guess something with a 30KOhms resistance is something really thin ?!

Anyway, I have used a new PCB to solder back the components. Now it’s seems to work fine. Can’t wait to test it in the field!