LCD Problem

[alexgraeme]

I have recently bought an A20 lime 2 and a 10" lcd ts but when i plug everything in and start it all up the lcd screen doesnt even turn on on i have it plugged into my computer through mini usb and a 4400mA battery attached, and also when i try to connect my board to my computer using a serial uart0 cable it cannot connect and it wont let me access the board to change anything such as resolutions. any help would be great. Could it be a simple case of the screen not getting enough power?

[dave-at-axon]

The 10" LCD according to the datasheet draws the same current as the 7" LCD so it should work with the battery and the USB connected.

Does the board boot with out the LCD connected?

Do you have a suitable power supply to connect to the LCD so that it is not drawing power from the A20?

[alexgraeme]

yes the board boots perfectly without the lcd connected and i do have a suitable 5v power supply but it seems to still not work might the board be defective?

[JohnS]

Probably not enough power or bad cabling, if you have the software config'd for the LCD.

John

[alexgraeme]

everything is brand new and ive tried hooking every combination of every power lead and the screen should start with a 7" resolution

[dave-at-axon]

Show us your FEX file for the 10"

It is different timing to the 7" panel.

Have a look at the datasheet. It is 51MHz and not 30MHz as per the 7"

Also the 10 is 1024 x 600 and the 7" is 800 x 480

Sounds like timing issue.

[alexgraeme]

How would i sort out the timing issue as when i try connect my board to my laptop using the USB-Serial cable it wont connect.

[dave-at-axon]

That sounds more like a power issue.

Run the board without the LCD connected. You can then use the UART to check it out.

What OS are you using?

[alexgraeme]

i have either ubuntu on VM or windows 8.1

[alexgraeme]

this is my script.fex file https://mega.co.nz/#!coZnlbZQ!TJ_h9z0j23yV7c2VDonT3geDD3R82RBLrsl8P4aGeeo

[dave-at-axon]

I mean which OS on the A20?

[dave-at-axon]

You're going to need to make changes to the FEX. It is set for HDMI (output_mode = 3) when it should be 1 for LCD.

Code Select Expand

screen0_output_type = 3
screen0_output_type = 3
screen0_output_mode = 4
screen1_output_type = 0
screen1_output_mode = 4



If you enable the LCD it will be set for 800 x 480

Code Select Expand

[lcd0_para]
lcd_used = 1
lcd_x = 800
lcd_y = 480
lcd_dclk_freq = 33
lcd_pwm_not_used = 0
lcd_pwm_ch = 0
lcd_pwm_freq = 1000
lcd_pwm_pol = 1
lcd_max_bright = 240
lcd_min_bright = 64
lcd_if = 0
lcd_hbp = 46
lcd_ht = 1055
lcd_vbp = 23
lcd_vt = 1050
lcd_vspw = 1
lcd_hspw = 30
lcd_hv_if = 0
lcd_hv_smode = 0
lcd_hv_s888_if = 0
lcd_hv_syuv_if = 0
lcd_lvds_ch = 0
lcd_lvds_mode = 0
lcd_lvds_bitwidth = 0
lcd_lvds_io_cross = 0
lcd_cpu_if = 0
lcd_frm = 1
lcd_io_cfg0 = 268435456
lcd_gamma_correction_en = 0
lcd_gamma_tbl_0 = 0x0
lcd_gamma_tbl_1 = 0x10101
lcd_gamma_tbl_255 = 0xffffff
lcd_power_used = 1
lcd_power = port:PH08<1><0><default><1>
pwm_used = 1


This guide shows you the settings.

http://linux-sunxi.org/Fex_Guide#.5Brtp_para.5D

You will need to find either a FEX file for the 10" LCD or modify the existing one and use that.

It certainly explains why you don't see anything on the LCD but don't explain the failure to boot as it should still do that but that could be a power issue. The LCD could be drawing higher power because it is not configured properly. Just a guess.

[alexgraeme]

right just by changing the screen output it has worked to boot the screen. it is reacing to touch like a 10 inch screen in a 7inch display. and when i try change the screen size the screen boots with no image. so now ive changed it to the lcd i need to change the resolution.

[alexgraeme]

now that im logged on on the display can someone help me ow to get it right?

[dave-at-axon]

Hi Alex,

As you seem to be able to modify the FEX, try the following setting in the FEX.

I assume as you are using script.fex that you are running Linux and not Android?

Code Select Expand


lcd_x = 1024
lcd_y = 600
lcd_dclk_freq = 51

lcd_hbp = 160
lcd_ht = 1344
lcd_vbp = 23
lcd_vt = 635
lcd_vspw = 5
lcd_hspw = 5


Note that I have only included the ones you need to change from your existing FEX.

You might need to change the lcd_vt to 2 x that value but give it a try first. Also I have selected vspw and hspw based on other displays I have used. The LCD datasheets show the limits for these. If not stable, increase of decrease these.

Another one you can play with is lcd_io_cfg0 and your current value is

Code Select Expand


lcd_io_cfg0 = 268435456


This is 0x10000000 and this can either be 0x0 or 0x20000000 to change the clock phase. It depends on the LCD timing. Your LCD RGB data is clocked in on the falling edge of the clock.