Game Boy Advance(GBA) LCD Interface

Manufactured by Sharp. Potential model numbers: LQU29B2DDO2P 18H00862812 or QPWBH2218TPZZ. Data-sheets unavailable.

40-Pin FFC Pinout

Pin	Name	Orig Sch Name	Description	Details
1	TST2	TST2
2	VSHD	TST1	Connected to VSHD
3	DCLK	DLCK	Pixel clock	Active on negative edge
4	LP	LP	Data latch of signal source driver (i.e pixel clock)	Active on positive edge
5	PS	PS	Power save signal	Active on positive edge
6	DGND	DGND	Digital ground
7	VSHD	VSHD
8	LDR5	R5	Bit 4 of digital red
9	LDR4	R4	Bit 3 of digital red
10	LDR3	R3	Bit 2 of digital red
11	LDR2	R2	Bit 1 of digital red
12	LDR1	R1	Bit 0 of digital red
13	LDG5	G5	Bit 4 of digital green
14	LDG4	G4	Bit 3 of digital green
15	LDG3	G3	Bit 2 of digital green
16	LDG2	G2	Bit 1 of digital green
17	LDG1	G1	Bit 0 of digital green
18	LDG0	G0	Labeled as bit 0 of digital green, but tied to ground	GND
19	LDB5	B5	Bit 4 of digital blue
20	LDB4	B4	Bit 3 of digital blue
21	LDB3	B3	Bit 2 of digital blue
22	LDB2	B2	Bit 1 of digital blue
23	LDB1	B1	Bit 0 of digital blue
24	SPL	SPL	Sampling start signal (HSYNC)	Active on positive edge
25	CLS	CLS	Clock signal of gate driver
26	SPS	SPS	Start signal of gate driver. f = 59.737Hz/ (i.e. VSYNC)	Active on negative edge
27	TST	TST3	Connected to VSHD
28	MOD	MOD	Control signal of gate driver
29	VCOM	VCOM	Common electrode driving signal	Active on positive edge
30	VEE	VEE
31	VSS	VSS
32	VCC	VCC
33	-	VDD
34	VSHA	VSHA
35	AGND	AGND	Analog ground
36	V4	V4	Voltage provided by AGB-REG chip on 40-pin GBA models. Check service manual.	Vpp=3.00V at 6.81KHz
37	V3	V3	Voltage provided by AGB-REG chip on 40-pin GBA models. Check service manual.	Vpp=2.32V at 6.81KHz
38	V2	V2	Voltage provided by AGB-REG chip on 40-pin GBA models. Check service manual.
39	V1	V1	Voltage provided by AGB-REG chip on 40-pin GBA models. Check service manual.	Vpp=3.72V at 6.81KHz
40	V0	V0	Voltage provided by AGB-REG chip on 40-pin GBA models. Check service manual.	Vpp=3.60V at 6.81KHz

32-Pin FFC Pinout

Pin	Name	Orig Sch Name	Description	Details
1	VSHD	TST1	Connected to VSHD
2	DCLK	DLCK	Pixel clock	Active on negative edge
3	LP	LP	Data latch of signal source driver (i.e pixel clock)	Active on positive edge
4	PS	PS	Power save signal	Active on positive edge
5	VSHD	VSHD
6	DGND	DGND	Digital ground
7	LDR5	R5	Bit 4 of digital red
8	LDR4	R4	Bit 3 of digital red
9	LDR3	R3	Bit 2 of digital red
10	LDR2	R2	Bit 1 of digital red
11	LDR1	R1	Bit 0 of digital red
12	LDG5	G5	Bit 4 of digital green
13	LDG4	G4	Bit 3 of digital green
14	LDG3	G3	Bit 2 of digital green
15	LDG2	G2	Bit 1 of digital green
16	LDG1	G1	Bit 0 of digital green
17	LDG0	G0	Labeled as bit 0 of digital green, but tied to ground	GND
18	LDB5	B5	Bit 4 of digital blue
19	LDB4	B4	Bit 3 of digital blue
20	LDB3	B3	Bit 2 of digital blue
21	LDB2	B2	Bit 1 of digital blue
22	LDB1	B1	Bit 0 of digital blue
23	SPL	SPL	Sampling start signal (HSYNC)	Active on positive edge
24	CLS	CLS	Clock signal of gate driver
25	SPS	SPS	Start signal of gate driver. f = 59.737Hz/ (i.e. VSYNC)	Active on negative edge
26	MOD	MOD	Control signal of gate driver
27	VEE	VEE
28	-	VDD
29	VSS	VSS
30	VCOM	VCOM	Common electrode driving signal	Active on positive edge
31	VSHA	VSHA
32	AGND	AGND	Analog ground

Signals Explained

The delta between the two cursors(neg edge of SPS) here is 16.743 ms, with a frequency averaging 59.728Hz, i.e. the refresh rate of the GameBoy Advance, indicating this is likely our VSYNC signal:

Zooming in, we can see that LP, PS, and SPL are all pulses that are active on the negative edge and each seem to represent the beginning of a pixel(each negative edge of the DCLK signal represents 15-bits of RGB being read by the display):

However, the PS signal is changed from a positive duty cycle of 85.699% to a positive duty cycle of 6.498% during the VBLANK period(SPS pulse followed by SPL pulse is the first pixel of the frame). This duty cycle change is shown here:

Resources

Portuguese GBA internal service manual

Contains acronyms for most of the 40-pins present on the Game Boy. This was super helpful when I was having trouble figuring out why my signals suddenly made no sense(my FFC was upside-down).
https://dragaosemchama.com/wp-content/uploads/2015/02/GBA-service-Manual.pdf

AlexiG's blog post

Great explanation of some of the LCD interface's signals. Wish I had found this sooner:
https://www.insidegadgets.com/2019/08/08/playing-around-with-the-gba-lcd/

Sharp LQ035Q7DH07 TFT-LCD Datasheet

An LCD datasheet from the same manufacturer as the GBA, although the LCD in the datasheet was manufactured 5-6 years after the Game Boy Advance.
https://www.mouser.com/datasheet/2/365/LQ035Q7DH07N_SPEC_LD-21910A-184021.pdf