Atharva
Posts: 13
Joined: Fri Mar 10, 2017 3:22 pm

HELP WITH 3.5 inch DISPLAY AND GPIO

Thu May 02, 2019 4:41 pm

Hello I wanted to create a handheld console with retropie and I have a waveshare 3.5 inch touchscreen display clone.The problem is that it is interfaced with gpio and i want to use some gpio for buttons as controls.Is it possible to save some pins for display as i don't want the touchscreen.Any help would be appreciated.

gordon77
Posts: 3895
Joined: Sun Aug 05, 2012 3:12 pm

Re: HELP WITH 3.5 inch DISPLAY AND GPIO

Thu May 02, 2019 4:43 pm

Which model waveshare?

Atharva
Posts: 13
Joined: Fri Mar 10, 2017 3:22 pm

Re: HELP WITH 3.5 inch DISPLAY AND GPIO

Thu May 02, 2019 4:45 pm

waveshare 3.5 inch model a

gordon77
Posts: 3895
Joined: Sun Aug 05, 2012 3:12 pm

Re: HELP WITH 3.5 inch DISPLAY AND GPIO

Thu May 02, 2019 4:50 pm

If it's this one https://www.amazon.co.uk/Waveshare-Rasp ... B01HR4CL6M with a 26pin connector then l assume you should have access to gpios on pins upto 40. You will probably need a right angled cable to connect to them.

Atharva
Posts: 13
Joined: Fri Mar 10, 2017 3:22 pm

Re: HELP WITH 3.5 inch DISPLAY AND GPIO

Thu May 02, 2019 5:04 pm

gordon77 wrote:
Thu May 02, 2019 4:50 pm
If it's this one https://www.amazon.co.uk/Waveshare-Rasp ... B01HR4CL6M with a 26pin connector then l assume you should have access to gpios on pins upto 40. You will probably need a right angled cable to connect to them.
but i need a joystick and four buttons i don't think they will be enough plus start shoulder buttons etc.
Last edited by Atharva on Thu May 02, 2019 5:06 pm, edited 1 time in total.

gordon77
Posts: 3895
Joined: Sun Aug 05, 2012 3:12 pm

Re: HELP WITH 3.5 inch DISPLAY AND GPIO

Thu May 02, 2019 5:05 pm

There are 9 gpios on pins 29 to 40, not enough?

Atharva
Posts: 13
Joined: Fri Mar 10, 2017 3:22 pm

Re: HELP WITH 3.5 inch DISPLAY AND GPIO

Thu May 02, 2019 5:09 pm

gordon77 wrote:
Thu May 02, 2019 5:05 pm
There are 9 gpios on pins 29 to 40, not enough?
need for shoulder buttons , start etc.
My calculations:
2 pins for joystick
4 pins for action buttons
2 buttons for start /stop
2 for right shoulder and left shoulder

gordon77
Posts: 3895
Joined: Sun Aug 05, 2012 3:12 pm

Re: HELP WITH 3.5 inch DISPLAY AND GPIO

Thu May 02, 2019 5:18 pm

There is a schematic here https://www.waveshare.com/wiki/File:3.5 ... ematic.pdf.

Looking at the 26pin connector they don't seem to be using a few pins labelled P1 to P4 and P7 , but l have no way of guaranteeing that.

Pi pins 8,10 and 5 also appear unused.

Beyond that you maybe able to use i2c but maybe others can comment on that.

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