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Tinker S with GPIO Touchscreen Ribbon cable issue
#1
Hi guys, this is obviously my first post here as i've been deep in the project i've started. this is my first time working with an SBC of any kind. they're pretty cool, but i've run into an odd issue i wasn't expecting.

the parts: Tinker Board S for SBC. Waveshare 4" HDMI LCD for the screen. ( This one, to be exact: www. waveshare .com/4inch-hdmi-lcd.htm) (link broke due to link protection?)
OS: TinkerOS Debian, newest from ASUS AU Site.
Connection: Display via HDMI, GPIO for touch and power. (a USB is available on the display for power only as well)

After a lot of pain and struggle. i discovered that making the touch work with the Tinker is actually stupidly easy... literally add 1 command line to the hardware init and it works...

However, this was directly connected. the housing i'm building the project into, however, doesn't have the space for the two parts to sit atop each other. so i had a 26 pin ribbon cable to bridge the gap... and this is where it went wrong. For some reason, the screen powers on, but does not display. Tinker boots normally (green activity light flashing normally) but only when the ribbon cable is used. if i connect directly again, it works fine.

i also tried connecting the screen with just the HDMI (leaving the GPIO disconnected) and powering the screen via the USB it has, and it displayed normally. so it's def not the HDMI cable. also the USB is power only. no touch functions will run via the USB as far as i'm aware.

i can't for the life of me figure out why this is happening or how to fix the issue... so i'm hoping that someone here with more knowledge and experience working with the Tinker and these kinds of projects in general, can help me get this project back on track...
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#2
not sure...
So you power your board from GPIO?
Do it also though ribbon cable?
if yes, may be the cable's resistance too high, and cause voltage drop and let current go low.
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#3
Sorry for the delay in replying. I'm not totally sure what the issue was, it was the ribbon cable but unsure as to why.

as to the specifics:
the GPIO provided power for backlight and touch, as well as data for touch. the Screen itself got its display data over HDMI. so i've no idea why the GPIO would cause a no display issue.

that said, i ended up buying a cable of about the right length with split up pin ends and carefully syncing that up. which works fine now.

the only thing i can think of is the cable resistance as you said. but i don't see why that would cause a no display issue when display is over HDMI and power, which appeared to be on due to the backlight, was over GPIO.

either way i got it sorted. i've been tinkering away on it for a while and pretty much only have software issues left to work with before i can call it done.
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