Screen using GPIO pins

[clytemnestra]

Hello all, I got a recent interest in pi and bought a pi3.

I bought a 5'' screen, but it seems the screen needs most of the GPIO pins. The screen fixates on the board on 4 long screws and then the two are connected through a small HDMI-HDMI.

I have two questions:

1. How can I make a case for this setup? I don't want to damage the boards, and sweat or greasy fingers on running circuits doesn't sound right.

2. How can I use the remaining GPIO if the screen takes most of them? I have a ribbon cable for the pins, but that one is kind of useless now since the screen is using them.

[texy]

Hi and welcome to the forum.
Looks like you bought the wrong display. Some designs have a GPIO pass-through connector for adding additional hardware. Otherwise you'll need to use some kind of adapter to 'break into' the cable path. You'll also need to establish with signals your particular display uses - almost certainly the SPI bus pins, plus perhaps 2 or 3 other general GPIO signals.
Texy

[clytemnestra]

Wrong? Should I return it? The screen I bought is this one

I wanted to use the PI for GPIOs but to also have a screen for it for easiness.


Note I'm a beginner, I can't really understand "You'll also need to establish with signals your particular display uses - almost certainly the SPI bus pins, plus perhaps 2 or 3 other general GPIO signals."

[texy]

Well maybe not 'wrong' , but it isn't ideal if you need to access the unused GPIO pins - which you do.
So we can see from the link that it is using the HDMI port for video but the Pi's SPI bus for the touch screen (the SPI bus is part of the GPIO port).
It does also have a table of which GPIO pins are unused for the display, so you can tell which other GPIO pins are free for your other hardware.
However it isn't going to be very easy to access the GPIO pins. IMHO I would choose a different display....

Texy

[BMS Doug]

Cases are good, help to protect your pi. Some people make their own wooden, plastic or metal cases, others buy premade cases and modify them as desired.

Wrong? Should I return it? The screen I bought is this one

I wanted to use the PI for GPIOs but to also have a screen for it for easiness.


Note I'm a beginner, I can't really understand "You'll also need to establish with signals your particular display uses - almost certainly the SPI bus pins, plus perhaps 2 or 3 other general GPIO signals."

The screen you have chosen gets it video signal from the HDMI connection, it uses the GPIO header for the touchscreen feedback. If you don't wish to use the touchscreen function then just using a longer HDMI cable will solve your issue.

This table from the page you linked tells which GPIO's the touchscreen uses, the NC pins are not connected and so are free for other use.

PIN NO. SYMBOL DESCRIPTION
1, 17 3.3V Power positive (3.3V power input)
2, 4 5V Power positive (5V power input)
3, 5, 7, 8, 10, 11, 12, 13, 15, 16, 18, 24 NC NC
6, 9, 14, 20, 25 GND Ground
19 TP_SI SPI data input of Touch Panel
21 TP_SO SPI data output of Touch Panel
22 TP_IRQ Touch Panel interrupt, low level while the Touch Panel detects touching
23 TP_SCK SPI clock of Touch Panel
26 TP_CS Touch Panel chip selection, low active

SPI is Serial Peripheral interface, a communications method between devices (in this case the touchscreen and the pi) some of these pins can be shared by multiple SPI devices if needed. The screen needs to use at most 8 of the GPIO pins, 6 of which will still be able to be used by other devices for the same purpose.

[texy]

The screen you have chosen gets it video signal from the HDMI connection, it uses the GPIO header for the touchscreen feedback. If you don't wish to use the touchscreen function then just using a longer HDMI cable will solve your issue.

Thanks Doug. The problem is getting access to the unused GPIO lines - the display board will still need power via the GPIO port.
Texy

[BMS Doug]

The screen you have chosen gets it video signal from the HDMI connection, it uses the GPIO header for the touchscreen feedback. If you don't wish to use the touchscreen function then just using a longer HDMI cable will solve your issue.

Thanks Doug. The problem is getting access to the unused GPIO lines - the display board will still need power via the GPIO port.
Texy

I would probably use a short ribbon cable with an extra connector.

[clytemnestra]

The screen can be placed in the GPIO slot and it will take both touchscreen and power from there OR HDMI and microUSB (it also works plugged in one of the pi's USBs, but not sure how much power it will take).

The problem with HDMI is that I don't know how to fixate it, because I have to place the screen somehow on the table, and it might damage it. The part where I place it in the GPIO is kind of keeping the screen and pi tied together.

Touch screen is also quite convenient to use, too. Will the used GPIOs affect my ability to properly use the pi for projects?

Another problem is that I can't really find other screens except the 3 or the 7 inch ones, but I thought 7 is not worth to buy since 5 is enough and it's at half the price of the 7 one.

[texy]

Will the used GPIOs affect my ability to properly use the pi for projects?

That depends entirely with the hardware you want to connect to. So your touchscreen uses the SPI bus, OK only 1 channel, but it more or less rules out those SPT specific pins for any additional hardware. What do you have in mind?
Texy

[clytemnestra]

That's the problem, I don't know yet what I want to do

First off, I'll do the LED circuit and a button one, then I want to make something more practical around the house, will see. All in due time, but I'd like to use the screen since it seems more practical (and I wasted money on it).

[clytemnestra]

So can I still use it for small projects with the remaining GPIO?

[texy]

Yes of course.

[clytemnestra]

What ability will it mostly hinder? Does it take anything important?

I found a 3D printing service in my town and don't want to spend the money if I'm going to be needing the other pins, too. Can't afford two cases, either.

Sorry for all the dumb questions.

[BMS Doug]

What ability will it mostly hinder? Does it take anything important?

I found a 3D printing service in my town and don't want to spend the money if I'm going to be needing the other pins, too. Can't afford two cases, either.

Sorry for all the dumb questions.

Yes, the 5v and 3v3 connections will be inaccessable under the connection.

If you are custom designing the case allow some seperation between the pi and the display and use a short 40 pin ribbon cable with an extra male connection for the screen. (You will need to split the ribbon after wire 26 to use this connector)

[clytemnestra]

I will also need an HDMI-HDMI, too it seems.

What's the difference between simply connecting them and using cables? Aren't I using the same pins for both the connection and the 26-pin male one?

[BMS Doug]

I will also need an HDMI-HDMI, too it seems.

What's the difference between simply connecting them and using cables? Aren't I using the same pins for both the connection and the 26-pin male one?

The additional connector on the ribbon cable will give you access to the gpio pins for other uses.

[clytemnestra]

I got a cable with 3 female(pcie cable). Would that work if I can get a male-male and connect the screen to one of it?

[drgeoff]

I got a cable with 3 female(pcie cable). Would that work if I can get a male-male and connect the screen to one of it?

If that is a cable for connecting PC hard drives to the motherboard make sure it does NOT have 80 wires. (40 wires for the 40 contacts in the female connectors and 40 for grounds between them to reduce cross-coupling.) Connecting one of those to a RPi will kill the RPi.

[mikronauts]

Put a board (with stacking connectors) between the Pi and the LCD add-on.



Pic above is one of my large prototyping boards connected to an Raspberry Pi A+ with a stacking header - it would be easy to plug one of the GPIO based LCD board on top of it.

I used a 40 pin tall stacking header with two spacers for my prototyping board.

Proto board: http://www.mikronauts.com/proto/ezaspieproto300/

Article pic came from: http://www.mikronauts.com/raspberry-pi/ ... rogrammer/

The screen you have chosen gets it video signal from the HDMI connection, it uses the GPIO header for the touchscreen feedback. If you don't wish to use the touchscreen function then just using a longer HDMI cable will solve your issue.

Thanks Doug. The problem is getting access to the unused GPIO lines - the display board will still need power via the GPIO port.
Texy

[BMS Doug]

Put a board (with stacking connectors) between the Pi and the LCD add-on.



Pic above is one of my large prototyping boards connected to an Raspberry Pi A+ with a stacking header - it would be easy to plug one of the GPIO based LCD board on top of it.

I used a 40 pin tall stacking header with two spacers for my prototyping board.

Proto board: http://www.mikronauts.com/proto/ezaspieproto300/

Article pic came from: http://www.mikronauts.com/raspberry-pi/ ... rogrammer/

That is a good solution for a permanent build, i got the impression that the OP wanted to be using solderless breadboard for messing about with I/O.

[clytemnestra]

That's what I do. I have a breadboard and want to play with the thing.

So, I have a 40-wires ribbon cable with 3 mother slots. Can I connect one of the mothers to the pi, one to the LCD and the other to the breadboard and have it all working? Just need to find a way for the LCD's mother to connect to the mother of the cable.

How does the pi know that it gets signal from the breadboard and not from the LCD in this case?

[texy]

With the exception of the ground and power pins just make sure each pi Gpio pin is only connected to one device.
For now at least, whilst you are learning.
Texy

[clytemnestra]

If I use the ribbon cable with the male for the screen, can I use the 5v and 3v pins used by the screen on the other female end? Will they get power and not interfere with the power taken by the screen?

The problem is the screen came with a small HDMI-HDMI thing that will only fit if the screen and pi are tied together. The alternative would be a HDMI cable, but the shortest I got is 1m length which is way too big.

Why is this so complicated..

[BMS Doug]

If I use the ribbon cable with the male for the screen, can I use the 5v and 3v pins used by the screen on the other female end? Will they get power and not interfere with the power taken by the screen?

Yes, that will be fine.

The problem is the screen came with a small HDMI-HDMI thing that will only fit if the screen and pi are tied together. The alternative would be a HDMI cable, but the shortest I got is 1m length which is way too big.

0.3m hdmi cables can be had fairly cheaply.

Why is this so complicated..

Sorry about that, hopefully it will all be worth it in the end.