maemo.org - Talk - View Single Post - N900 LCD/display Problem

	Marshall Banana	2012-10-20 , 15:20
	Posts: 94 \| Thanked: 209 times \| Joined on Oct 2009 @ Germany	#1

The problem
When i start my N900 the LED lights up, the startup vibration happens and the LCD-backlight is turned on for a short moment. But after that the display doesn't work anymore. I can't see the Nokia logo or the five blinking dots. TV-out does not work properly, i can just see one horizontal line in the middle of the TV screen. The notification light works and the touchscreen seems to work, when i tap on it i can hear the usual clicking sound.

How i caused the problem
The earpiece of my N900 stopped working, i could only hear the call partner with headphones or speakers switched on. The earpiece problem maybe started after i dropped the phone some time ago, but i'm not sure. After reading some earpiece issue repair threads like this i disassembled my N900 and readjusted the earpiece contacts. After i reassembled the N900 i discovered my new LCD/display problem.

How i tried to fix the problem
Replace LCD-module - didn't work
Replace flex-cable-assembly - didn't work
After checking LCD and flex-cable i enabled R&D mode and looked at the output of the serial console (see wiki: Debug ports, sample serial dump)

serial output with old display attached:

Code:

ÿNOLO X-Loader (v1.4.14, Jun  3 2010)
Secondary image size 109384
Booting secondary
[   0.002] Nokia OMAP Loader v1.4.14 (Jun  3 2010) running on Nokia N900 F5 (RX-51)
[   0.014] I2C v3.12
[   0.033] System DMA v4.0
[   0.036] OneNAND device ID 0040, version ID 0121 (256 MiB, 66 MHz)
[   0.071]   OneNAND blocks unlocked in 28056 us
[   0.075]   Flash id: ec4021
[   0.090] Partition table successfully read
[   0.097] TWL4030 PWR ISR: 01
[   0.101] Reset reason: pwr_key
[   0.104] McSPI v2.1
[   0.107] LP5523 found at I2C bus 2, address 0x32
[   0.118] SMB138C: Not loading driver (version reg. 0x4b)
[   0.124] BQ24150 (rev. 3) found on I2C bus 1, address 0x6b
[   0.130] SSI version 1.0
[   0.144] Battery voltage 3.732 V, BSI: 0
[   0.154] Disabling charging (no battery present)
[   0.165] Polling power key...
[   1.158] Initializing LCD panel
[   1.161]   Detecting LCD panel moscow
[   1.165]     Panel ID: 10af02
[   1.168]   Detected LCD panel: acx565akm
[   1.172] DISPC: version 3.0
[   1.177]   LCD pixel clock 24000 kHz
[   1.208]   Logo drawn in 5 ms (11700 kB/s)
[   1.491]   Über-cool backlight fade-in took 161 ms
[   1.496] Initializing USB
[   1.504]   No USB host detected
[   1.507] Loading kernel image info
Loading kernel (1744 kB)... done in 63 ms (27519 kB/s)
[   1.579] Loading initfs image info
[   1.583] Total bootup time 1598 ms
[   1.587] Serial console disabled
Uncompressing Linux..................................................................................................................... done, booting the kernel.

Observations:

LCD-panel get's detected
Panel ID: 10af02 (serial dump in the wiki: Panel ID 108d77)
über-cool backlight fade-in took 161 ms (serial dump in wiki: 9 ms, dunno if this duration has any meaning)

serial output with new display attached:

Code:

ÿNOLO X-Loader (v1.4.14, Jun  3 2010)
Secondary image size 109384
Booting secondary
[   0.002] Nokia OMAP Loader v1.4.14 (Jun  3 2010) running on Nokia N900 F5 (RX-51)
[   0.014] I2C v3.12
[   0.033] System DMA v4.0
[   0.036] OneNAND device ID 0040, version ID 0121 (256 MiB, 66 MHz)
[   0.071]   OneNAND blocks unlocked in 28042 us
[   0.075]   Flash id: ec4021
[   0.090] Partition table successfully read
[   0.097] TWL4030 PWR ISR: 01
[   0.101] Reset reason: pwr_key
[   0.104] McSPI v2.1
[   0.107] LP5523 found at I2C bus 2, address 0x32
[   0.118] SMB138C: Not loading driver (version reg. 0x4b)
[   0.124] BQ24150 (rev. 3) found on I2C bus 1, address 0x6b
[   0.130] SSI version 1.0
[   0.144] Battery voltage 3.724 V, BSI: 0
[   0.154] Disabling charging (no battery present)
[   0.165] Polling power key...
[   1.158] Initializing LCD panel
[   1.161]   Detecting LCD panel moscow
[   1.165]     Panel ID: 108d77
[   1.168]   Detected LCD panel: acx565akm
[   1.172] DISPC: version 3.0
[   1.177]   LCD pixel clock 24000 kHz
[   1.208]   Logo drawn in 5 ms (11700 kB/s)
[   1.490]   Über-cool backlight fade-in took 160 ms
[   1.495] Initializing USB
[   1.503]   No USB host detected
[   1.506] Loading kernel image info
Loading kernel (1744 kB)... done in 63 ms (27520 kB/s)
[   1.578] Loading initfs image info
[   1.582] Total bootup time 1597 ms
[   1.586] Serial console disabled
Uncompressing Linux..................................................................................................................... done, booting the kernel.

Observations:

LCD-panel get's detected
Panel ID: 108d77 (same as in wiki)
über-cool backlight fade-in took 160 ms (serial dump in wiki: 9 ms)

serial output with no display attached:

Code:

ÿNOLO X-Loader (v1.4.14, Jun  3 2010)
Secondary image size 109384
Booting secondary
[   0.002] Nokia OMAP Loader v1.4.14 (Jun  3 2010) running on Nokia N900 F5 (RX-51)
[   0.014] I2C v3.12
[   0.033] System DMA v4.0
[   0.036] OneNAND device ID 0040, version ID 0121 (256 MiB, 66 MHz)
[   0.071]   OneNAND blocks unlocked in 28042 us
[   0.075]   Flash id: ec4021
[   0.090] Partition table successfully read
[   0.097] TWL4030 PWR ISR: 01
[   0.101] Reset reason: pwr_key
[   0.104] McSPI v2.1
[   0.107] LP5523 found at I2C bus 2, address 0x32
[   0.118] SMB138C: Not loading driver (version reg. 0x4b)
[   0.124] BQ24150 (rev. 3) found on I2C bus 1, address 0x6b
[   0.130] SSI version 1.0
[   0.144] Battery voltage 3.724 V, BSI: 0
[   0.154] Disabling charging (no battery present)
[   0.165] Polling power key...
[   1.159] Initializing LCD panel
[   1.163]   Detecting LCD panel moscow
[   1.166]     Panel ID: 000000
[   1.170] ERROR: Unknown panel ID
[   1.173]     not detected
[   1.175] ERROR: No LCD panel detected
[   1.179] Initializing USB
[   1.187]   No USB host detected
[   1.190] Loading kernel image info
Loading kernel (1744 kB)... done in 63 ms (27577 kB/s)
[   1.262] Loading initfs image info
[   1.266] Total bootup time 1278 ms
[   1.270] Serial console disabled
Uncompressing Linux..................................................................................................................... done, booting the kernel.

Observations:

LCD-panel doesn't get detected
Panel ID: 000000
no über-cool fading

serial output with old display attached and R&D mode and serial-console flag:
Pastebin

Observations:

LCD-panel get's detected
Panel ID: 108d77 (same as in wiki)
über-cool backlight fade-in took 9 ms (serial dump in wiki: 9 ms)
Kernel has issues with display:
[ 3.026672] acx565akm spi1.2: invalid display ID
[ 3.031402] omapfb omapfb: can't get display 0

Concluding remarks:
The LCD is connected to the omap via SPI, there seems to be some communication problem because:

the LCD doesn't display anything
display id sometimes doesn't get read correctly
kernel complains about invalid display ID and missing display

Did i damage the connector on the mainboard, the esd-filter (see N900 schematics p. 5) or maybe there is some voltage supply problem?
My next step will be to connect somehow to the flex connector socket on the n900 mainboard and measure some voltages and look at the SPI lines with my logic analyzer. But i have no idea how to interface with this tiny connector

Any help would be appreciated.

Last edited by Marshall Banana; 2012-10-20 at 15:22. Reason: Wrong link

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