This has been asked and answered many times, but my specific question is not in the list of results when I search.

I have a nominal 2.6A supply here, and it remains stable at 5V up to exactly this amp load with no voltage drop. It’s quality. So I would just like to know if I need to do some resistor magic/short-circuit on the TX/RX lines for it to work perfectly with my pi3.

I’ve observed on most quality 5V supplies that RX/TX are shorted, and I am aware of apple’s weird voltage divider circus on their iPhone/iPad PSUs - but this is a Pi - does it even pay attention to RX/TX signal lines?

My expected max load is 1.5-2A, not more. I’ll pull an extra 5V rail from this PSU for something else nearby.

Let me know if I need to clarify.

Note: I’ve used a 2.1A iPad charger up to now, and it does not work well at all. Even when I observe a load of only 1.3A, there are not-enough-power indicators when I attach 50mA USB peripherals. A standard off the shelf charger at 2A has no issues... But I need the extra 5V rail for something else nearby.

TL;DR: I am connecting 5V/GND to a male microUSB breakout board, and need to know if using resistors or shorting the data lines (the aforementioned RX/TX) will in any way affect the Pi’s operation. If so, how?

Update: The PSU wasn’t the issue; I was using too thin, too long a cable. At the Pi I measured 5.10V when it was turned off, but ~4.85V when on and loaded. So I should read 5.25V at the Pi when it’s off:/

  • Could you explain what the RX/TX lines are? I can make no sense of the question. I can't see any relevance to the Raspberry Pi.
    – joan
    Mar 25 '18 at 15:04
  • Receive and transmission lines in a standard USB1.1/2 cable. I’m connecting the 5V/GND to the 5V/GND pins on a little male microUSB breakout board, and am curious to know if the RX/TX pins are relevant. See electronics.stackexchange.com/questions/123172/… . I would have asked on EE.SE, but they’d obviously say this question belongs here.
    – user2497
    Mar 25 '18 at 15:08
  • For posterity: A value of 0-200 ohms between the data pins on USB1/USB2 informs a device that this power source conforms to the DCP section of USB Battery Charging Specification, i.e. a source capable of providing <= 1.5A.
    – user2497
    Mar 25 '18 at 17:47

The Pi's microUSB power socket is only connected to pins 1 (5V) and 5 (ground). Pins 2, 3, and 4 are not connected.

Schematics at https://www.raspberrypi.org/documentation/hardware/raspberrypi/schematics/README.md


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.