USB Cable: IDE port interface w/ Data Lines only

Hardware
1

Is there any restrictions on using a USB cable with only the Data + & - lines running the IDE?
On two different IDE installations using only the DATA + and DATA - lines there is no communications with the microcontroller.
I have IDE 2. on a Windows 11 desktop and IDE 1.8.19 on a laptop running Windows 10 and neither will communicate to an ESP32 with just the Data lines employed.

I cut the power wire only and tried to establish communications and the port hookup was not 'recognized'. I then cut the ground wire and there was no change in the problem.

I resoldered the wires and the cable worked as expected indicating the data lines are functional.

I wanted to be able to link up to a microcontroller with just the data lines and leave its separate power input wires connected. I don't know if hooking two power sources up simultaneously to a microcontroller is a wise idea. Intuitively it seems wrong. I believe the +5 volt pin on the controller has some commonality with the USB port voltage input.

Is there something I am overlooking to make a 2-wire comm hookup work?

2

Two power sources can cause a problem, it depends if the board was designed for that. If you are powering the board some other way, BUT you also need the Serial port then maybe just the two data lines will work, but I don;t know how Serial works and if itg works the same way on every board. There may be a case where you need USB data and power in order to see Serial output but I don't know for sure.

3

For now it is a matter of getting out my tiny flathead screwdriver and removing a terminal wire..... just not quite as convienent.....but not everything is....

4

I think you need a common data ground also. Just disconnect the +5V wire and leave the other 3 connected.

5

Noy sure what a 'common data ground' is. If you mean the D- and the G pins are connected, maybe you can get out your VOM and tell us if that is the case. Also, check if the case of the male USB connector is connected to any of the 4 pins although I will bet if it is it will be either G or D- or both.

6

The 4 wires in a USB cable are independent, separate from each other. If you want to have a data only USB cable, just disconnect the +5V (usually red) wire.

7

When you first cut the USB 5V, did you provide another way to power the esp32?

8

That was attempted when I first just severed the 5 volt line, leaving the remaining three intact.

9

Yes .....
original post:
"I wanted to be able to link up to a microcontroller with just the data lines and leave its separate power input wires connected."

11

I am not sure we are on the same page. If you disconnected the USB power wire, did you then attach a wall wart or battery power wire to the alternate pin often called VIN to power the board. If you didn't, the board would not operate. You either have to provide power via USB or via some other power source to some pin on the board. Maybe a drawing?

12

Your opening post stated the below :smiley:

There is no mention of a GND. As you can see, you need to be very clear in your descriptions. Schematics / wiring diagrams make it a lot clearer what you did :wink:

Obviously boards need to be powered. So if you did cut Vcc you will need to provide power in another way.

Some boards have protection; the Nano can safely be powered with 5V on the 5V pin or 7V-12V on Vin and at the same time use USB. An Uno or Mega can be powered on Vin (7V-12V) and at the same time be powered from USB but it shouldn't be powered with 5V on the 5V pin and USB at the same time.

1 Like
13

Fom my original post:

This was all in reference to the USB cable:
Data+ yellow ; Data - white ; 5v red ; Ground black.

Cutting first the red wire with no resulting communication. Cutting next the ground wire with still no communication.

Obviously.... I never tampered with the power wire feeding the ESP. I wanted to interface with the ESP32 WITHOUT having to disconnect its external power feed. If there is no risk of damage to the ESP having both the USB powered and a separate supply to the 5 volt input pin then that is all I need to know. It would be interesting to discover why more than just Data - and Data + is needed to make the USB port hookup work. I know some USB cables are made 'comm only.'

14

D+ and D- are differential signal lines and must be referenced to common ground.

15

So if it was going to ever work it would have been with just the red dc supply wire cut. There is something quirky about it. Some things are gonna work and some won't. What I really need to do is get OTC working and that would make all this unnecessary.