Need help to drive an lcd RGB 24 bits screen

pawnies20 · April 12, 2015, 11:37:10 PM

Hello!
I need some help.
I'm trying to drive this screen:
http://www.sat-sz.com/data/SAT040HS54DHY0-A0_20140909.zip

I'm using two differents voltages: one for backlight and another for lcd power.

I read documentation behind to configure fex:
http://linux-sunxi.org/Fex_Guide
in fex, i'm using this parameters:

lcd_x=320
lcd_y=240
lcd_dclk_freq=6
lcd_hbp=38
lcd_ht=408
lcd_vbp=18
lcd_vt=524
lcd_hv_vspw=1
lcd_hv_hspw=1

lcd_if=0
lcd_lvds_bitwidth=0
lcd_io_cfg0=0
lcd_bl_en_used=1
fb0_scaler_mode_enable=0
fb0_width=0
fb0_height=0
I want to use 24 bits RGB with data (23:0), Hsync, Vsync and DE.

I'm using this map too:
https://github.com/OLIMEX/OLINUXINO/blob/master/HARDWARE/A10-OLinuXino-LIME/A10_Lime_GPIOs.pdf?raw=true

I ve found this doc too:
https://github.com/allwinner-ics/lichee_linux-3.0/blob/master/drivers/video/sun4i/lcd/a10_lcd_config_nanual_v1.0.pdf

But Nothing, id did not work...

In lcd page 15 there is register table .
I don't know how to use it with flex...

I don't understand

Thank you

dave-at-axon · April 13, 2015, 05:51:35 AM

Can you show us a schematic of the LCD interface board you have that connects the 40 pin from the Olimex to the 54 pin on the LCD?

What's strange for me is that there is no reference to the backlight voltage requirements, only current is shown. How are you driving the LED's for this?

The document is very poor. There is also no reference to what state the SPIENABLE has to be for RGB mode. I am assuming this is high?

Also the reference to the SPI shows different signal name and uses the I2C naming convention.

jmyreen · April 13, 2015, 09:05:59 AM

Quote from: dave-at-axon on April 13, 2015, 05:51:35 AM
What's strange for me is that there is no reference to the backlight voltage requirements, only current is shown. How are you driving the LED's for this?

According to the schematics, there are four diodes in series. The forward drop is probably quite high. From Wikipedia: "Typically, the forward voltage of an LED is about 1.8–3.3 volts; it varies by the color of the LED. A red LED typically drops 1.8 volts, but voltage drop normally rises as the light frequency increases, so a blue LED may drop around 3.3 volts." This means over 13 volts may be needed to drive the LEDs.

Once you are over the forward drop, you can assume the resistance of the LEDs are zero, so some kind of current limiter is needed to keep the current within spec.

dave-at-axon · April 13, 2015, 10:03:38 AM

Yeah, I figured around 14V or so. My display uses 6 in each of 2 sets of series LED's and is 19V. It's good practice if the display manufacturer actually quotes the LED forward voltage so you can setup the correct current and voltage.

If there is no backlight, you cannot tell if the LCD timing is correct as you will see nothing unless of course you had one of those transflective displays but they are not very common and expensive too.

pawnies20 · April 13, 2015, 10:05:59 AM

thanx for reply.
Voltage for backlight is 13V, your are agree jmyreen and works well with an external power.
Dave i will make the connexion table in few hours!
Many many thanx

pawnies20 · April 13, 2015, 10:13:03 AM

this is the table:

reset->1 (3.3V)
data 0-23->LCD_D0-LCD_D23 (i respect order PD0-PD23)
hsync->LCD_Hsync (PD26)
vsync->LCD_Vsync PD27
dotclk->LCD_CLK PD24
vdd->3.3V
den->LCD_DE PD25
gnd->GND

backlight :cathode gnd and anode: external power (with gnd connected) and 13v)

Thank you

dave-at-axon · April 13, 2015, 11:31:25 AM

What voltage have you connected SPIENABLE to?

Try connecting this to 3.3V if not already done so.

pawnies20 · April 13, 2015, 01:09:29 PM

Spiennable is not connected.
You think it could be the problem?
What about timings?

Thank you very very very much !!

dave-at-axon · April 13, 2015, 01:52:53 PM

If it disables the SPI then yes, it could be the reason for no image.

Timings seem OK looking at the datasheet.

What OS are you using?

pawnies20 · April 13, 2015, 02:02:20 PM

Thanx dave!!
I'm using debian

pawnies20 · April 13, 2015, 10:45:01 PM

I have tried to connect Spi ennable to 3.3v
Nothing change.

I don't understand

pawnies20 · April 13, 2015, 10:56:27 PM

I'm using olimex debian .
I think when i'm export fex to bin it will work after reboot.
I have no command to launch?

pawnies20 · April 13, 2015, 11:37:37 PM

my lcd use this ic:
http://www.texim-europe.com/promotion/402/ili9322%20driver%20datasheet_te.pdf

pawnies20 · April 14, 2015, 12:37:00 AM

Dave, can you explain me how you get newhavendisplay to work well?

http://www.newhavendisplay.com/nhd35320240mfatxlctp1-p-5204.html

You are using debian or android?

Can you explain me the differents steps?

You say on another post:
I use the 5" and 7" models and they have the same interface.

I recently got the 7" working with an A20 running Android.

The screen use differents ics to drive.

Can you explain me please?
Thank you

dave-at-axon · April 14, 2015, 02:38:31 AM

I use Android and I build my own OS so that I have full control over the FEX settings etc. Some of us tried to modify the FEX in the pre-built images but it didn't work. The only solution was to build a custom OS. I have now got 2 builds that can run with the Touch Revolution or Newhaven displays. In fact, I can build for any display and touch with this.

What OS are you using and are you building this yourself?

Looking at the datasheet for your display it should be defaulting to RGB according to the SPI registers but I also see that there are 2 pins to select the mode. These are internal to the module so you can't select these.

I think the issue is to ensure that your FEX is being read on power up. Can you capture the debug output from the board UART as this is so important as it will show what your OS is attempting to setup the system for. Post it here so we can see it.