Hitachi VGA TFT LCD module

The display module

Main parameters

Manufacturer	Hitachi Displays, Ltd.
Model number	TX26D60VC1CAA
Resolution	640 x 480 pixels (VGA)
Stripe organization	R,G,B
Color depth	6 bit per channel, approx. 256 thousands of colors
Source	a broken AST Ascentia 910N

Parameters

Interface connector

Update 07/29: The connector is called Hirose DF9. I believe it should be a DF9B-31P-1V. The matching connector should be DF9-31S-1V. Other similar connectors (e.g., JAE made this type of connectors too, and has its own number) are possible too. (Serina)

Interface connector from perspective

The interface itself has 31 pins in two lines (16+15):

Pin	Signal	Description
1	Vss
2	DCLK	Dot clock
3	HSYNC	Horizontal synchronization
4	VSYNC	Vertical synchronization
5	Vss
6	R0	Red data, LSB
7	R1	Red data
8	R2	Red data
9	R3	Red data
10	R4	Red data
11	R5	Red data, MSB
12	Vss
13	G0	Green data, LSB
14	G1	Green data
15	G2	Green data
16	G3	Green data
17	G4	Green data
18	G5	Green data, MSB
19	Vss
20	B0	Blue data, LSB
21	B1	Blue data
22	B2	Blue data
23	B3	Blue data
24	B4	Blue data
25	B5	Blue data, MSB
26	Vss
27	DTMG	Data timing
28	Vdd
29	Vdd
30	Vdd
31	NC	Leave unconnected, could be TEST signal

Display interface signals

Display cable

The following cable was used in the AST Ascentia 910N laptop:

The counterpart of the display interface connector

Motherboard side of the interface cable

If we separate the cable ending into two parts, let's say A and B, then A will have 26 wires and the B part 20 wires. Signal assignment was reverse engineered from the laptop's mainboard and the datasheet of the graphic controller. Measuring the unknown wires (other than ground and power) lead to these results:

Pin	Part A	Part B
1	Detection loop	Vss
2	Vss	G5
3	Vss	G4
4	Detection loop	R5
5	Detection loop	R4
6	Vss	Vss
7	Vss	B5
8	Vdd	HSYNC
9	Vdd	DTMG
10	R3	VSYNC
11	R2	B4
12	R1	N.C.
13	R0	Unknown backlit signal
14	Vss	Vss
15	G3	Vss
16	G2	Vss
17	G1	Backlit on/off
18	G0	Backlit power
19	Vss	Backlit power
20	B3	Backlit power
21	B2	-
22	B1	-
23	B0	-
24	Vss	-
25	DCLK	-
26	Vss	-

Motherboard side of the cable

Power

The similar module (TX26D01VM1CAA) described in an available datasheet (link on the end) has a Vdd=3.3V, but my meauserements on the AST laptop indicated a 5V voltage on the Vdd signal, so in the testing application I used also a 5V source and it worked (during few hours of testing, when I will be able to get a regulated supply, I make additional tests to find out whenever is the module able to run on 3.3V).

Update 07/29: This module should also run at 3.3V, if I'm not mistaken. (Serina)

Backlit

The backlit inverter was originally powered by 15.5 - 16 V DC from the AC adapter (at least when the laptop run on AC, I did not get it to run from battery) however it was working also on 12V DC.

Backlit on/off signal is specified as a TTL signal, but in the testing application i've simply connected it to te backlit power pin. There is also one unknown signal from or to the backlit unit, I haven't discovered yet what it can be, maybe an intensity control signal.

Update 07/29: Inverters usually take two types of signals, brightness control and on/off. Different voltage through BRT control results in different brightness. (Serina)

TODO: further testing needed on brightness control. When it will work, a simple D/A converter from resistors should be enougn, e.g. 4 bit for 16 brightness levels. (I'll put here some info in few days/weeks I hope)

Timing diagram

The timing diagram is based on the timing of a similar module, namely TX26D01VM1CAA.

Timing diagram

Update 08/04: The parameters of the timing are quite the same as written in VESA Safe Mode Timing standard, only in Vsync, the 34 and 35 are the values which differs, but maybe only because of interpretation problems.

Parameter	Name	Value			Unit
Parameter	Name	minimal	normal	maximal	Unit
t_DCLK	Dot clock period		40		ns
t_HP	Horizontal period	785	800		t_DCLK
t_HBP	Horizontal back-porch		144
t_HFP	Horizontal front-porch	1	16
t_WH	Horizontal active width		96
t_VP	Vertical period	515	525		t_HP
t_VBP	Vertical back-porch		34
t_VFP	Vertical front-porch	1	11
t_VW	Vertical active width		4

Timing parameters

Example/testing application

The functionality of the module and the proper timing values were verified using the following wiring to the parallel port a PC:

TFT signal	TFT pin	LPT pin	LPT signal	Power suppy
DCLK	2	2	D0	-
DTMG	27	3	D1
HSYNC	3	4	D2
VSYNC	4	5	D3
R0-5	6-11	6	D4
G0-5	13-18	7	D5
B0-5	20-25	8	D6
Vss	1, 5, 12, 19, 26	18-25	GND	GND
Vdd	28, 29, 30	-	-	+5V

Module to PC connection for tests

You can download my driver and the following stripes test patter program - tx26d60vc1caa.tar.bz2.

Testing application - stripes

The display is also able to show nice bitmaps:

Testing application - bitmap

Future

Now, when I know that the panel is working, there are several ways to continue:

Connecting to analog VGA signal using an ADC
Connecting to a graphic card for embedded applications - using digital RGB data
Making an own graphics card with FPGA and memory chips, the best it would be for USB2 interface

If you feel that you can help me with realizing one of them, please contact me.

Used documents

TX26D01VM1CAA display datasheets
http://www.hitachi-displays-eu.com/doc/tx26d01vm1caa.pdf

Further information

VESA SMT - Safe mode timing standard
http://www.vesa.org/public/SMT/SMT640_720x480V1.pdf

Acknowledgements

Mr.StY
(tools & cable)
Honza Bernatík
(photos)
Serina Chung, www.radiancedisplay.com
(information update)