Tuesday, 3 January 2017

Pi Zero: adapting the USB socket

Although the Raspberry Pi Zero is about half the size of a credit card, the connectors stick out sideways, which affectively increases the boards footprint once connected.

To make matters worse, the USB socket is the micro version, so you need an adaptor if you only have a standard USB wifi dongle.

So in order to make a really small, headless Zero system, you need to do something radical.

Although the Pi Zero was released just over a year ago, I only bought my first Zero a couple of weeks before Christmas. The original  board was upgraded a few months after initial release and a camera connector added. This makes the Zero a good choice for a headless camera project.

Micro this, micro that...

The use of micro USB and HDMI connectors was a natural choice, given the designers need to shrink the board. But the user still needs to connect a supply and a device or two, which will increase the footprint of your system. This is probably not an issue for a Pi Zero connected to a monitor and keyboard.

However, for headless projects, it is quite annoying to have to find a box twice the width of the board just to accommodate the wifi dongle. Most wifi adaptors still use a standard USB connector. So when I bought my Pi Zero from PiHut for £4, I found myself spending another £2 on a USB/micro adaptor ...crazy!

Although micro USB wifi dongles have started to appear (like this one from ModMyPi)  the vast majority are still standard USB...

Pi Zero + Edimax dongle via adaptor

...and whether you use either the ModMyPi dongle or the Edimax Nano with an adaptor, the overall width increases from 30mm to almost 55mm.

Time to hack

 So I wondered whether I could hack the board and add a standard USB connector.

Looking down on the component side of the Pi Zero, I could see that the USB connections were much too close together for me to approach with my 18W soldering iron. I would simply end up with (at least) 3 board short-circuits.

Flipping the board over looked more promising. I noticed a number of pcb pads which I assume are used for pin-bed A.T.E. testing. Two of these pads appeared to be beneath the micro USB connector and they looked like a big enough target for my shakey soldering iron hand.

A quick prod around with my multimeter confirmed they were connected to the USB data pins. Using and old USB cable (which I'd previously cut one end off)  I was able to confirm the required connections to a standard USB socket.

Pi Zero pads:-
  • P1 = +5V
  • P6 = 0V
  • P22 = data +
  • P23 = data -

Looking into the standard USB socket, with the orientation key at the top, the pin designations are:-

So I took four lengths of single core wire from an old length of CAT5 cable, and wired the socket to the required pads...

...it won't win any prizes for presentation, but hey! it works.

Even a dual band Edimax AC600 fits within the area of the board.


It should be possible to fit a headless Pi Zero + wifi into a box with interior dimensions of approx: 70mm high x 35mm wide x 15mm deep, if 5V power is connected directly to the gpio (pin 4 = 5V, pin 6 = 0V).

I'm hoping I can connect a RaspiCam and solder a 78B5.0 regulator directly to the gpio and run from 12Volts. The minimum interior dimensions would then be either:-
  1. with the camera above the Zero: approx 80mm high x 35mm wide x 30mm deep
  2. with the camera at one end: approx 100mm high x 35mm wide x 30mm deep

...although finding a suitable box close to these dimensions will be a challenge. I got a couple of boxes on order, including this one from Spiratronics. I think the Zero will just fit between the internal pillars of the box!

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