mowensmd
Posts: 3
Joined: Sat Feb 06, 2016 5:42 pm

7" screen not powering on

Sat Feb 06, 2016 6:04 pm

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I bought the official 7" touchscreen for my son. I helped with install, and the instructions online are pretty good. I attached pics of the connections we made which I believe are correct. He has a 2 B v 1.1 from 2014, so we didn't use the yellow and green jumper cables (though I did try them after getting stuck trying to get the screen to turn on). I used the HDMI out to view a monitor to update and upgrade the software. So I think I followed the guide well, used 3 different ways to power the 2 boards (USB, jumper wires and separate AC) but with many reboots, the touchscreen just doesn't power on. Help?

JimmyN
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Re: 7" screen not powering on

Sun Feb 07, 2016 11:23 am

I know you said you upgraded, but lets have a look to see what you're running. What do you get from this command?

Code: Select all

uname -a
You can power it with any of the methods you mentioned, your power jumpers look OK. You are correct you don't need the two I2C wires if you're using a Pi2 B. The ribbon cable is turned the right way.

When you power it up do you see anything from the display, does the backlight turn on?
With both HDMI and the display connected, do you see anything on the TV/monitor when you power it up?

mowensmd
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Joined: Sat Feb 06, 2016 5:42 pm

Re: 7" screen not powering on

Mon Feb 08, 2016 2:59 am

When you power it up do you see anything from the display, does the backlight turn on?

No, it stays dark regardless of method for power.


With both HDMI and the display connected, do you see anything on the TV/monitor when you power it up?
Yes, HDMI out to a monitor shows the Pi booting and is how I did the update and upgrade.

Thanks for your help so far!

JimmyN
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Re: 7" screen not powering on

Mon Feb 08, 2016 2:10 pm

It would seem it's not initializing since it's still defaulting to HDMI. Let's make sure the module is loading. Use the "lsmod" command and see if you have "rpi_ft5406" in the list.

If the "rpi_ft5406" module is loaded check the voltage on the displays "5V" and "GND" pins to verify it actually has power.

The other item to check would be the white ribbon cable between the DSI connector on the Pi and the display adapter. One end may not be seated all the way. The display won't initialize if that cable is not fully inserted and connected properly.

Also show us what you get with a "vcgencmd get_config int" command. Let's make sure the display isn't turned off in config.txt.

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DougieLawson
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Re: 7" screen not powering on

Mon Feb 08, 2016 9:48 pm

It looks like your ribbon cable is in upside down. Mine has the blue writing on the inside of the cable.
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Re: 7" screen not powering on

Mon Feb 08, 2016 10:43 pm

DougieLawson wrote:It looks like your ribbon cable is in upside down. Mine has the blue writing on the inside of the cable.
Looks OK to me. The contacts on the two ends are on opposite sides. The contacts on the Pi end should be facing into the middle of the board, and they are.
The instructions off the swag store also show it that way with the writing on the outside - https://cdn.shopify.com/s/files/1/0174/ ... 3104331728
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mabrown
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Re: 7" screen not powering on

Sat Feb 13, 2016 8:07 pm

Never mind, I just found the answer. I needed to power the screen from a PSU and power the Pi from the board. I was doing the reverse.

I'm experiencing the same issue. The display doesn't appear to turn on at all. I'm powering via USB on a Pi 2 with Raspbian Jessie with latest updates.

Code: Select all

pi@raspberrypi:~ $ uname -a
Linux raspberrypi 4.1.17-v7+ #840 SMP Sat Feb 13 15:19:36 GMT 2016 armv7l GNU/Linux

Code: Select all

pi@raspberrypi:~ $ lsmod
Module                  Size  Used by
rpi_ft5406              2826  0
cfg80211              399468  0
rfkill                 16799  1 cfg80211
snd_soc_bcm2708_i2s     6648  0
regmap_mmio             2969  1 snd_soc_bcm2708_i2s
bcm2835_gpiomem         3023  0
bcm2835_rng             1824  0
snd_soc_core          131952  1 snd_soc_bcm2708_i2s
snd_compress            7725  1 snd_soc_core
snd_bcm2835            19739  3
snd_pcm_dmaengine       3287  1 snd_soc_core
spi_bcm2835             7216  0
snd_pcm                75040  3 snd_bcm2835,snd_soc_core,snd_pcm_dmaengine
snd_timer              19138  1 snd_pcm
snd                    52636  11 snd_bcm2835,snd_soc_core,snd_timer,snd_pcm,snd_compress
uio_pdrv_genirq         2986  0
uio                     8228  1 uio_pdrv_genirq
i2c_dev                 6108  0
fuse                   82598  3
ipv6                  343556  30
As you can see, rpi-ft5406 is loaded. I'm getting ~5V across the display's 5V and GND pins.

Code: Select all

pi@raspberrypi:~ $ vcgencmd get_config int
arm_freq=900
audio_pwm_mode=1
audio_sdm_mod_order=2
config_hdmi_boost=5
disable_commandline_tags=2
disable_l2cache=1
emmc_pll_core=1
force_eeprom_read=1
force_pwm_open=1
framebuffer_ignore_alpha=1
framebuffer_swap=1
hdmi_force_cec_address=65535
init_uart_clock=0x2dc6c0
lcd_framerate=60
over_voltage_avs=0x1b774
overscan_bottom=32
overscan_left=32
overscan_right=32
overscan_top=32
pause_burst_frames=1
program_serial_random=1
sdram_freq=450
temp_limit=85
I appreciate any help you can provide. Let me know what other diagnostic info I can provide.
Thanks!
--mab[/s]

mowensmd
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Re: 7" screen not powering on

Fri Mar 04, 2016 3:49 am

I thought you only had to power either the board or the screen?

6by9
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Re: 7" screen not powering on

Fri Mar 04, 2016 10:19 am

mowensmd wrote:I thought you only had to power either the board or the screen?
The red and black wires link the two boards for power, but the (very strong) recommendation is that you then plug the PSU into the display board (not the Pi).
The Pi copes better with the supply being slightly low on volts than the display does.

You don't need two power supplies as long as your one is up to the task.
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emilyopearson
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Re: 7" screen not powering on

Thu Nov 01, 2018 5:32 pm

I'm having a similar problem, however, when I try "lsmod" the touchscreen is not showing that it's reading. What does this mean?

I had this exact assembly working a month ago, then set aside to work on another project. No one has touched it so I'm confused why it's not working now.

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