Raspberry Pi: Unresponsive keyboard problem solved with a customised USB cable

After collecting the various things requisite to operate the RPi (HDMI to DVI cable, 8GB SD card with OS image, micro USB cable, low power USB keyboard and mouse), I eagerly plugged it all in and watched the boot screen flash by… Awesome.

Raspberry Pi Login:

Type pi

Nothing appears on screen. No characters.

Bash keyboard a bit…

Still nothing.

Conscious that the power supply (iPad charger, rated 5v, max 2.1amps) might be at fault (having read that the iPad charger wasn’t really up to the job of powering the Pi), I tested the board voltage with a multimeter across the labelled test points ‘TP1’ and ‘TP2’ on the board. It looked like the voltage was cycling between 3.5v and 4.5v – that’s not correct at all – and the power LED was also suspiciously flickering! I tried a similarly rated power supply (one gifted by my energy supplier with their ‘iPlan’ home energy monitor), which did make a tiny difference to the cycling voltage values, but otherwise the board behaved the same – receiving no keyboard input at all.

I then tried another USB cable (from a Samsung mobile phone), and this did make a difference – the voltage no longer cycled up and down, but was still apparently too low for the keyboard to operate.

So I’d tracked at least part of the problem down to a dodgy micro USB cable. Frustrated by the lack of Pi desktop action, and faced with the prospect of spending money on A) a powered USB hub or B) another cable and/or power supply that may or may not have even worked, I had nothing really to lose by taking a scalpel to the cheaper USB cable (which had only cost me just 68p including postage on Amazon!). I figured I would simply try and connect the terminals with some thicker gauge wire to reduce the cable’s resistance, and whilst I was in there, also remove the unnecessary data cables, which weren’t doing any good for power purposes. Here’s a montage:

1) micro end of USB cable, with internal wires laid bare

2) The micro USB end decapitated, with data cables removed

3) micro USB end, with thicker wires

4) USB end, ready to be modded

5) The finished, upgraded power cable!

I connected the modified cable to the iPad charger and Pi, and eagerly watched the boot screen flash by… Awesome.

Raspberry Pi Login:

Type pi

pi appears on screen

Celebrate.

I checked the voltage across the board test points, and found a stable voltage of 4.9v (with my alternative power supply, a stable 5v)! Job done.

Err… Now what?

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