brron
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Vertical lines only

Fri Mar 31, 2017 9:18 pm

I received an official 7" touchscreen earlier in March, but still have not been able to use it. The screen only shows a white background with randomly colored vertical lines. If the ribbon cable is in more snugly, it starts white and the background fades to black, and then the screen blinks black once and then returns to black background with rainbow vertical lines. I have tested the ribbon cable with an ohmmeter and each pin works. I have tried both sides on the adapter and raspberry pi 3. I have tried with and without the green and yellow jumpers. Nothing seems to work. Any ideas?

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topguy
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Re: Vertical lines only

Mon Apr 03, 2017 8:59 am

Have you enabled the screen with "raspi-config" ?

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DougieLawson
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Re: Vertical lines only

Mon Apr 03, 2017 6:11 pm

Since you have a B+, 2B or 3B then pull the green and yellow wires off. Unless you have an old RPi1 you do NOT need to connect the I²C pins (#3 & #5 on your RPi) to the SDA/SCL pins (#2 & #3) your display.

Make sure the display is wired to the right 15pin ribbon socket (the one near the end of the board next to the power connector, NOT the one between the ethernet and the HDMI).
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brron
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Re: Vertical lines only

Tue Apr 04, 2017 2:37 am

topguy wrote:Have you enabled the screen with "raspi-config" ?
Which setting would that be?
DougieLawson wrote:Since you have a B+, 2B or 3B then pull the green and yellow wires off. Unless you have an old RPi1 you do NOT need to connect the I²C pins (#3 & #5 on your RPi) to the SDA/SCL pins (#2 & #3) your display.

Make sure the display is wired to the right 15pin ribbon socket (the one near the end of the board next to the power connector, NOT the one between the ethernet and the HDMI).
The green and yellow wires are out, and the right ribbon socket is being used. I have adjusted each ribbon cable in each user-available location. Sometimes I get more black lines than white lines, and I think this has to do with the quality of the connection. But I've done it a dozen times, and each time the ribbon cables have fit very snugly. I am at a loss.

What I think is either my RPI is broken (I have another thread where the microsd got burning hot and the wifi-chip stopped working, which is near the ribbon connector) or the screens chip in its ribbon cable is broken.

6by9
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Re: Vertical lines only

Tue Apr 04, 2017 11:06 am

First step is to connect an HDMI monitor at the same time as the display. The Pi will only drive one display at a time, so therefore if the HDMI monitor stays blank the basic link between the Pi and controller board is working and you need to look at the connection from display board to the display. If the HDMI monitor is active, check the connection from Pi to display.
If you have managed to fry your Pi then all bets are off as it could have fried parts of an interface.

Please remember that the display is not designed for hotplugging, therefore power down before moving connections around.
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topguy
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Re: Vertical lines only

Tue Apr 04, 2017 11:52 am

brron wrote:
topguy wrote:Have you enabled the screen with "raspi-config" ?
Which setting would that be?
My apologies, I thought there was an option for the display in raspi-config just as it is for the camera. If there is, it is very well hidden I could not find it either.

6by9
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Re: Vertical lines only

Tue Apr 04, 2017 12:00 pm

topguy wrote:My apologies, I thought there was an option for the display in raspi-config just as it is for the camera. If there is, it is very well hidden I could not find it either.
No, it's not there. The display controller is probed over I2C by the firmware on boot, and if it responds everything switches to using it instead of HDMI.
Software Engineer at Raspberry Pi Trading. Views expressed are still personal views.
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elkberry
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Re: Vertical lines only

Tue Apr 04, 2017 5:18 pm

6by9 wrote:First step is to connect an HDMI monitor at the same time as the display. The Pi will only drive one display at a time, so therefore if the HDMI monitor stays blank the basic link between the Pi and controller board is working and you need to look at the connection from display board to the display. If the HDMI monitor is active, check the connection from Pi to display.
If you have managed to fry your Pi then all bets are off as it could have fried parts of an interface.

Please remember that the display is not designed for hotplugging, therefore power down before moving connections around.
Major nitpicking alert here :mrgreen: the RPi actually has both outputs active, but the framebuffer used by Linux is mapped to the DSI-connected display layer. The HDMI layer is also "active", but since no app uses its allocated output plane, nothing to be seen there in case the 7" Touch LCD was correctly identified. But for diagnosing, the simple explanation is sufficient. It's even possible to clone the LCD/DSI display to the HDMI display...
From ZX81 to Raspberry Pi, but wait ... where's the 7805 gone?

brron
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Re: Vertical lines only

Tue Apr 04, 2017 8:03 pm

6by9 wrote:First step is to connect an HDMI monitor at the same time as the display. The Pi will only drive one display at a time, so therefore if the HDMI monitor stays blank the basic link between the Pi and controller board is working and you need to look at the connection from display board to the display. If the HDMI monitor is active, check the connection from Pi to display.
If you have managed to fry your Pi then all bets are off as it could have fried parts of an interface.

Please remember that the display is not designed for hotplugging, therefore power down before moving connections around.
Having HDMI connected at the same time makes the HDMI screen black, so it does detect it. And when the ribbon cable is not connected, the touchscreen stays black. But when the ribbon cable is connected, it's just vertical lines. So the ribbon cable is being detected, but it's not fully transferring the display.

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DougieLawson
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Re: Vertical lines only

Tue Apr 04, 2017 8:16 pm

So you have to assume it's a faulty ribbon cable or a faulty display.

Try it with another Raspberry. Try another display with this Raspberry. Try another ribbon cable.
Note: Any requirement to use a crystal ball or mind reading will result in me ignoring your question.

Criticising any questions is banned on this forum.

Any DMs sent on Twitter will be answered next month.
All non-medical doctors are on my foes list.

brron
Posts: 6
Joined: Sun Mar 19, 2017 12:03 am

Re: Vertical lines only

Sat Apr 08, 2017 4:01 am

DougieLawson wrote:So you have to assume it's a faulty ribbon cable or a faulty display.

Try it with another Raspberry. Try another display with this Raspberry. Try another ribbon cable.
Finally managed to get my hands on another Raspberry Pi 3, and the thing worked immediately. It must have been the old Pi that had the wifi chip broken too. At least now I have a control group so I can find out what else is broken on that Pi :D.

Thanks everybody.

gaunch
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Re: Vertical lines only

Fri Sep 29, 2017 3:02 am

I had this same problem out of the box. I did not have another Pi to test the 7" touchscreen with, so I kept trouble shooting.

It turns out I was not seating the ribbon cable properly. For anyone else out there still facing this problem, try reseating the ribbon cable and make sure you close the FCB connector by pushing the small bar in after seating the cable.

I did not realize how these connectors worked so was missing this last step. After reseating everything I found this tutorial: https://forums.pimoroni.com/t/raspberry ... embly/1132 which helped immensely.

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