Wednesday, 4 February 2015

Raspberry Pi Diary - Breakout Boards

Interfacing 101

One of the main reasons why I bought the Raspberry Pi was to bring together the two worlds of electronics and computing for my two youngest sons. The oldest of the two already has various components and breadboard to play about with, and he's already been experimenting with scratch for a while now.

The great thing about the Raspberry Pi is that it has those GPIO pins just waiting to connected to LEDs, switches, sensors or the wide variety of add-ons that you can buy these days. I thought I'd start by getting a simple breakout board from Maplin.

GPIO Breakout Board
I got one, but lets just say I made a few mistakes!

Mistake #1

It comes in kit form, requiring the ribbon socket and header pins to be soldered together before you can use it. There's a simple diagram that suggests how the ribbon connector should connect to the GPIO pins and which way it should fasten into the breakout board. Seemed simple enough but it wasn't obvious which way up the board should go.

One end of the breakout board
One end was labelled 'GPIO HEADER' (see diagram), so I concluded that it belongs this way up and started soldering the socket. After I'd done about eight I started to get the niggling feeling that it wasn't correct. I stopped and traced the wiring only to find I actually had the board upside down!!!

Now unsoldering a double-sided board is a nightmare, and my desoldering pump just wasn't doing the job. In the end, I levered the socket away from the board leaving the soldered pins still attached. These were then individually removed with a hot soldering iron and a pair of pliers.

Botched breakout board with removed socket pins.
Now I'll have to drill out the remaining solder before I can start again. (This wasn't going well!)

Mistake #2

It wasn't until my son came through to check how I was getting on that I realised my next mistake. I was explaining to him about how the ribbon plug would fit into the GPIO. When I went to demonstrate this I spotted my next mistake. (this one pretty fatal)

This was a 26 pin breakout board for the original Raspberry Pi, but I'd bought the newer RPi B+ model, which has a 40 pin GPIO. The ribbon plug won't fit and if you try to force it you'll end up bending some of the pins. (darn!)

Let's do it Right

All I can say is "Cobblers" - or to be more exact Adafruit's T-Cobbler Plus. As soon as I opened the bag I was immediately impressed by the improved quality and the neat screen printing showing (without doubt) which way the socket should be soldered.

You can bet I still checked it carefully before I started, but within about 10 minutes it was done.

The assembled Adafruit T-Cobbler Plus
My son quickly relieved me of it and started building a circuit to light his 7 segment LED display.

(More about that another day)


  1. Saw this and thought of you:

    (they don't actually mean Graphic EQ, it's an LED project, but a very nice one)

  2. Nice - yeah they mean spectrum analyser that often formed part of the graphic equaliser. But we know what they meant.

    You can get little dot matrix displays quite cheaply, and at some stage I'll get one. Most of the example projects I've seen use them for displaying characters though. This is way cooler!