I need to access the serial log without charging the battery attached to the board.
The board is a RAK4631.
I am thinking if i cut the +5V line in the usb cable that leaves the TX, RX amd GND.
That should be enough to use the cable as a serial connection but it will not charge the battery.
Has anybody tried this or has some other idea?
I have exactly the same problem and was going to engage in exactly the same activity as well.
Chances are these two products would do what you needed in combination.
Good suggestion.
I didn’t have time to wait for it to arrive in the mail so I took an old cable and removed the plastic on one of the connectors. Having it connected i could see the log on my computer but when I cut the +5V on the cable the serial connection goes down. I get the same behaviour on both RAK4631 and TBeam.
I assume the usb circuit on the board is running of the +5V supplied on the board.
My conclusion is that this is not a possible way to go.
I’ve used these to provide only 5v via dupont pin headers, but they’d probably work pretty well for the opposite case:
In the Ender 3 community, we have a similar problem with certain older mainboards possibly backfeeding >5V into your computer. It is solved by covering the 5V pin with a small piece of tape as shown here:
The data lines work just fine, but no power will flow.
That is a nice nondestructive way to do it.
I think it would give the same result as when i cut the +5 line in the cable: the serial connection dies. I think the usb part of the board is not powered from the battery and needs the +5 from the outside.
I tested both RAK4631 and TBeam.
Chances are you could remove the trace or a surface mount resistor on the RAK board to disable the power flow between the two.
The problem I was trying to find in the logfiles was false low voltage readings. I added a counter to trigger low voltage state (and sleep) if there was 4 readings in a row instead of going to sleep on the first.
It turned out to be a good guess and the fix was included in 1.2.46 .
… and I don’t trust my soldering skills and equipment enough to remove surface mounted stuff 