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Using GPIO pins along with piggyback 5 inch HDMI display

Posted: Wed May 17, 2017 5:59 am
by Severian
I was pleasantly surprised to find some 5 inch HDMI LCD monitors on Amazon recently for under 30 dollars. They appear to be clones of a Waveshare designed module, although I did not know that when I ordered. They plug into the top 26 pins of the GPIO on my Raspberry Pi 3 and give a nice 800x480 display. The GPIO pins are used to make the touch screen work. I'll configure that later, since I am only using text mode for now. (I am driving the second framebuffer for a second monitor and that only works if I launch the program from text mode). My problem is using the other 14 GPIO pins. I want to have 3 or 4 push buttons connected for user input. A standard ribbon cable or jumper cable goes up too high to allow the monitor to fit on the GPIO pins. An extension for the GPIO pins is not a good idea, because the tiny adapter that goes between the HDMI ports on the Pi and the monitor would no longer fit. I found a jumper wire (2 pin male to 2 pin female) at a local electronics store that does fit. The connector on the female end is much shorter than most jumper connectors. If there is interest, I can post a picture of it beside a standard jumper wire. The owner of the store does not know what these reduced size connectors are called. I want to document and post about the build and I'd like to know the proper name for the part and maybe even someplace else to buy them. Tanners in Dallas is great, but he only has a few more left. Can someone point me to the proper name or another source? I have been googling all afternoon, but I can't get a useful incantation.
I want something like "jumper wire short header female to male(or female)"
Or, if there is some other good solution, let me know. I have had similar issues using Raspberry Pi hats where I wanted to use GPIO pins not needed by the hat and I never found a good general solution.

Re: Using GPIO pins along with piggyback 5 inch HDMI display

Posted: Wed May 17, 2017 6:47 am
by aTao
Soldering the jumpers directly to these:

Will give you a low profile connector.

If you want one that does not even protrude above the pin then you might solder cut down female connector inserts directly to a pcb: ... dp/2499384 with the cable grip parts removed

Re: Using GPIO pins along with piggyback 5 inch HDMI display

Posted: Wed May 17, 2017 8:37 am
by davidcoton
With any cut-down solution, make sure you put decent insulation between the top of the pins and the display, or between pins if they are not already insulated. A single layer of insulating tape is prone to wearing through if there is any movement.

Re: Using GPIO pins along with piggyback 5 inch HDMI display

Posted: Thu May 18, 2017 10:43 pm
by Severian
Thank you Tao and David,
I think I can make something of those parts. The detail I did not mention is that these parts will be installed by people who are not experienced with electronics. I will do an initial build and document it. Any replacement parts or new kits will likely bbe put together by people in small villages in remote places like Papua New Guinea. I have lots of respect for the people, but my conversations suggest they don't do a lot of electronic assembly.
Have a wonderful day.