iankincaid
Posts: 5
Joined: Thu Feb 15, 2018 8:35 pm

Composite output flashing

Thu Mar 26, 2020 1:27 am

I have a Vehicle security tft monitor display I am trying to plug Into my Raspberry Pi. When I start my Pi, I have to hold the shift key for about 5 seconds then press either the 3 or 4 keys to get the display to come on. But when it does, it is flashing on and off so fast, I can barely see what is on the screen, but I can tell it isn't displaying properly (colorful and garbled). I have messed around with the config.txt but nothing is working!! Does anyone have any suggestions?

fruitoftheloom
Posts: 21995
Joined: Tue Mar 25, 2014 12:40 pm
Location: Delightful Dorset

Re: Composite output flashing

Thu Mar 26, 2020 4:30 am

iankincaid wrote:
Thu Mar 26, 2020 1:27 am
I have a Vehicle security tft monitor display I am trying to plug Into my Raspberry Pi. When I start my Pi, I have to hold the shift key for about 5 seconds then press either the 3 or 4 keys to get the display to come on. But when it does, it is flashing on and off so fast, I can barely see what is on the screen, but I can tell it isn't displaying properly (colorful and garbled). I have messed around with the config.txt but nothing is working!! Does anyone have any suggestions?

Presumably you are using a correctly wired TRRS4 Cable ?
Model-B-Plus-Audio-Video-Jack-Diagram.png
Model-B-Plus-Audio-Video-Jack-Diagram.png (22.72 KiB) Viewed 213 times
Retired disgracefully.....
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Rather than negativity think outside the box !

iankincaid
Posts: 5
Joined: Thu Feb 15, 2018 8:35 pm

Re: Composite output flashing

Fri Mar 27, 2020 12:19 am

fruitoftheloom wrote:
Thu Mar 26, 2020 4:30 am


Presumably you are using a correctly wired TRRS4 Cable ?

Model-B-Plus-Audio-Video-Jack-Diagram.png
Actually I thought of that, and it could be the problem but from what I've heard, if I was using the wrong cable, the display wouldn't work at all. And it does come on, it just flashes repeatedly, and is skewed and glitchy. Could using a camcorder cable cause that?

klricks
Posts: 6842
Joined: Sat Jan 12, 2013 3:01 am
Location: Grants Pass, OR, USA
Contact: Website

Re: Composite output flashing

Fri Mar 27, 2020 3:09 am

iankincaid wrote:
Fri Mar 27, 2020 12:19 am
fruitoftheloom wrote:
Thu Mar 26, 2020 4:30 am


Presumably you are using a correctly wired TRRS4 Cable ?

Model-B-Plus-Audio-Video-Jack-Diagram.png
Actually I thought of that, and it could be the problem but from what I've heard, if I was using the wrong cable, the display wouldn't work at all. And it does come on, it just flashes repeatedly, and is skewed and glitchy. Could using a camcorder cable cause that?
Is your TV NTSC (US) or PAL (UK)? I think the RPi default out is NTSC. If PAL then you need to adjust a setting in config.txt.
If you are using a camcorder cable (Sony, Panasonic etc), then RED of the cable needs to be connected to YELLOW of the TV.
If the ground is in the wrong position as in the MP3 cable in the above chart, then the image will be severely distorted and will never work.
Unless specified otherwise my response is based on the latest and fully updated Raspbian Buster w/ Desktop OS.

drgeoff
Posts: 10321
Joined: Wed Jan 25, 2012 6:39 pm

Re: Composite output flashing

Fri Mar 27, 2020 12:18 pm

iankincaid wrote:
Fri Mar 27, 2020 12:19 am
fruitoftheloom wrote:
Thu Mar 26, 2020 4:30 am


Presumably you are using a correctly wired TRRS4 Cable ?

Model-B-Plus-Audio-Video-Jack-Diagram.png
Actually I thought of that, and it could be the problem but from what I've heard, if I was using the wrong cable, the display wouldn't work at all. And it does come on, it just flashes repeatedly, and is skewed and glitchy. Could using a camcorder cable cause that?
Sounds like you have the wrong cable of the type which results in the video and ground being swapped over. That gives the TV an inverted signal. Most TVs will attempt to display that inverted signal but it will be distorted and have no colour. See https://www.raspberrypi.org/forums/view ... 22#p653422 for an example.

iankincaid
Posts: 5
Joined: Thu Feb 15, 2018 8:35 pm

Re: Composite output flashing

Fri Mar 27, 2020 5:09 pm

drgeoff wrote:
Fri Mar 27, 2020 12:18 pm
Sounds like you have the wrong cable of the type which results in the video and ground being swapped over. That gives the TV an inverted signal. Most TVs will attempt to display that inverted signal but it will be distorted and have no colour. See https://www.raspberrypi.org/forums/view ... 22#p653422 for an example.
I switched out the cable and it fixed the color and distortion. The image now looks completely clear. However, it is still flashing (on any tv I try it on). It's not just a little flash either. It comes on for about half a second and then flashes off, and does this repeatedly. Could that be the cable or a setting on the Raspberry Pi?

fruitoftheloom
Posts: 21995
Joined: Tue Mar 25, 2014 12:40 pm
Location: Delightful Dorset

Re: Composite output flashing

Fri Mar 27, 2020 5:55 pm

iankincaid wrote:
Fri Mar 27, 2020 5:09 pm
drgeoff wrote:
Fri Mar 27, 2020 12:18 pm
Sounds like you have the wrong cable of the type which results in the video and ground being swapped over. That gives the TV an inverted signal. Most TVs will attempt to display that inverted signal but it will be distorted and have no colour. See https://www.raspberrypi.org/forums/view ... 22#p653422 for an example.
I switched out the cable and it fixed the color and distortion. The image now looks completely clear. However, it is still flashing (on any tv I try it on). It's not just a little flash either. It comes on for about half a second and then flashes off, and does this repeatedly. Could that be the cable or a setting on the Raspberry Pi?



https://www.raspberrypi.org/documentati ... t/video.md
Retired disgracefully.....
......to an uncomplicated life !

Rather than negativity think outside the box !

iankincaid
Posts: 5
Joined: Thu Feb 15, 2018 8:35 pm

Re: Composite output flashing

Sat Mar 28, 2020 5:11 am

*UPDATE*
I've figured out my problem: I had been trying to power my 12V display with a 9V battery pack, because I had missed where it said what power supply to use on the box. :lol:
Sorry to anyone who has been inconvenienced, and thank you all for the wonderful help! This was such an annoying problem and I'm glad it's fixed. Seems like such an obvious thing but... :lol:
Just a reminder: always read the box :lol:

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