markysoft
Posts: 9
Joined: Fri Sep 09, 2011 9:40 am

Cable For Multiple GPIO board?

Thu Aug 20, 2015 2:42 pm

I have an LCD screen attached but would like to daisy chain another board from the GPIO pins.

Does anyone know if I can get a cable that has two connectors (like an old hard disk IDE cable), or is there another way to achieve this?

I found this http://www.amazon.com/ribbon-cable-Rasp ... B00G84WNA2 but not sure if that would do the trick.

Thanks,
Mark

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mikronauts
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Joined: Sat Jan 05, 2013 7:28 pm
Contact: Website

Re: Cable For Multiple GPIO board?

Thu Aug 20, 2015 3:17 pm

First:

Check what I/O pins the display uses. Odds are it is using /CE0, /CE1, MISO, MOSI, CLK - basically the SPI port with both chip selects.

It may use additional I/O - ask the vendor of your display.

Second:

You can stack boards between your Pi and the LCD, *AS LONG AS* they don't use the GPIO's the LCD uses.

You are S.O.L. (So Out of Luck) if you want to use the pins the LCD is using.

Third:

You can always add I/O expanders, they won't be as high speed as the Pi native GPIO's but they are more than enough for most purposes.

Examples:

Only uses I2C lines
http://www.mikronauts.com/raspberry-pi/pi-rtc-dio/

Only uses serial Rx, Tx and GPIO#17, can be used as a sophisticated I/O expander
http://www.mikronauts.com/raspberry-pi/robopi/
http://Mikronauts.com - home of EZasPi, RoboPi, Pi Rtc Dio and Pi Jumper @Mikronauts on Twitter
Advanced Robotics, I/O expansion and prototyping boards for the Raspberry Pi

markysoft
Posts: 9
Joined: Fri Sep 09, 2011 9:40 am

Re: Cable For Multiple GPIO board?

Thu Aug 20, 2015 7:49 pm

Thanks for the response.

I'm connecting a noisepower socket controller http://noisepower.co.uk/mains-control-raspberry-pi, a Waveshare 3.2″ LCD, which would then be connected to a small circuit board that uses Ground, GPIO4 and the 3.3V line.

The cicuit board and the noisepower socket controller play nice together, and it sounds like my small board would work with the LCD as it's only using GPIO4.

Unfortunately I'm not able to connect the LCD and the noisepower board at the same time at moment to check those. If they worked would the stacked header be suitable? I don't need an additional board, just a way of attaching an additional cable if they are all compatible.

ame
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Joined: Sat Aug 18, 2012 1:21 am
Location: Korea

Re: Cable For Multiple GPIO board?

Thu Aug 20, 2015 11:53 pm

markysoft wrote: Does anyone know if I can get a cable that has two connectors (like an old hard disk IDE cable), or is there another way to achieve this?
This is achieved by buying additional IDC connectors and squeezing them down onto the cable. You can put as many as you like along the length of your ribbon cable. There is a tiny triangle moulded onto the outside of the connector, which indicates pin 1. You should line it up with the red stripe on the cable (or whatever polarizing indicator the cable has) and then squeeze the parts together in a vice. Plan carefully, the connectors are difficult if not impossible to remove once they are installed (and they make a mess of the cable if you do).

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rpdom
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Location: Chelmsford, Essex, UK

Re: Cable For Multiple GPIO board?

Fri Aug 21, 2015 6:05 am

Make sure it is an old 40-pin IDE cable with all 40 holes on the connector. Many connectors had one hole blanked off to prevent the connectors being plugged in the wrong way round.

Also newer cables used 80 wires with some of the pins shorted together inside the plugs, which could fry your GPIO quite easily. The easy way to tell if it is 40 or 80 wire is to count the first ten wires. If you have barely touched the cable it is 80 way and unusable. If you are about a quarter of the way across then it is 40 wire and probably OK.

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