GPIO breakout

GPIO Extender Card - version 1

In Portsdown, there are up to 13 signals that need to be routed in or out of the GPIO interface on the RPi. Buying an extender card early in the project reduces the chance of damage to the RPi and allows these connections to be made safely. The card must break out all 40 pins of the GPIO, and have another connector on top for the LCD display.

Because of this the Portsdown team have designed a PCB for the job - the blank PCB is available from the BATC shop. (If you bought a breakout card from Willow it can still be used, but we recommend you use this card and put the Willow card in your next project box.)

The BATC card is very simple to construct with no components other than plugs and sockets.

The circuit is available for download here:

File:PORTSDOWN INTERFACE SCH.pdf.

You can buy the GPIO Extender Card blank PCB from the Portsdown section in the BATC shop - item 6 

The "extra tall stacking header" to connect to the Rpi is available from Adafruit -  https://www.adafruit.com/product/1979
Or from the Pi hut

The white sockets in the picture above are used to connect to other Portsdown boards and are available from Farnell or you can just hard wire from the pads on the board and pass the wires through the large holes behind the pins.

5 Pin 9731636      http://uk.farnell.com/molex/22-05-7058/header-tht-right-angle-2-54mm/dp/9731636 
4 Pin   9731628    http://uk.farnell.com/molex/22-05-7048/connector-header-tht-ra-2-54mm/dp/9731628 
3 pin 9731610       http://uk.farnell.com/molex/22-05-7038/connector-header-tht-ra-2-54mm/dp/9731610

Or you can use screw terminal - Farnell part numbers as follows:

3 Way 2396254
4 Way 2396253
5 Way 2112483
6 Way  2396255    (only required to connect to a DigiThin modulator - a previous BATC project and not part of the Portsdown project)

Portsdown GPIO extender - version 2

Some changes to the original Portsdown interface were needed with some GPIO changes on the Raspbery PI 4, unused functions were removed and additional ones added.

Parts list here File:Portsdown Interface V2-12 parts.xlsx# Schematic here File:PD 4 INTERFACE V2-12.pdf

GPIO list for the Raspberry 4 with Portsdown here https://wiki.batc.org.uk/Portsdown_4_GPIO_Connections  

The Raspberry PI 4 runs hotter than the Raspberry pi 3 so consideration must be given to allow more space for air flow. I stand off the PCB to accommodate air flow.