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Display Connector

A project log for MIPI-HDMI Bridge RE

Reverse-Engineering a random MIPI-HDMI bridge from China

Jared SansonJared Sanson 10/29/2019 at 05:190 Comments
The connector provides two independent MIPI channels, each with 4 data pairs & 1 clock pair. The 5V rail is always powered, but the other rails can be individually sequenced and controlled by the MCU. The GPIOs can be used to control additional regulators or enable control signals on the display board. They are output only.

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I do not know what chip "ET7" and "MH 23 22" are, but they are obviously some kind of buck regulator. A/B/C/D are the GPIO control signals from the MCU (output only).
E6 enables the 3.3v rail, and supplies the 1.8v regulator. IOC/D are powered even if this rail is not.
E4 enables the 1.8v rail to the display connector, but only if E6 is also enabled (for 3.3v). IOA/B are pulled-up to 1.8v if this is enabled.
The 5V rail is always powered.
I am not sure what the deal is with the chip at the top that is fed directly from +5v.

TFT Backlight Driver

For TFTs, there is a dedicated backlight driver:
V3 is +V for the backlight, and either FB1/2 can probably be chosen for -V depending on the drive strength that is desired.
E9 is obviously an analog feedback signal to the MCU for controlling the drive current, E5 is the main supply enable, and E8 is probably a PWM control signal for defining the drive current.

OLED Bias Voltage

E7 enables the bias circuit.

E10 is probably a PWM drive signal for controlling display brightness.

On my board, the following signals come up in this order when it is powered on:
A: Slow Flashing Blue LED / Initial power-up

B: Fast Flashing Blue LED

C: Green LED


You can see that on my board, the LED backlight & OLED bias supplies are never turned on. Instead the dsplay board has it's own regulators which are controlled by the IOA/B/C/D GPIOs.


Full connector pinout:

Number

Net Name

Voltage

Breakout Net

Use

Description

1

FB1




Feedback 1

2

FB1




Feedback 1

3

-





4

-





5

FB2




Feedback 2

6

FB2




Feedback 2

7

-





8

V3




Backlight

9

V3




Backlight

10

V3




Backlight

11

-





12

GND





13

V1




OLED Bias (E7+E10 Ctrl)

14

V2




OLED Bias (E7+E10 Ctrl)

15

-





16

-





17

-





18

-





19

IOA

1.8

G

Right OLED Enable?

E4 Ctrl

20

IOB

1.8

F

Right OLED Enable?

E4 Ctrl or Always powered?

21

-





22

V_1.8

1.8

E

1.8v Supply

E4 Ctrl

23

-





24

V_3.3

3.3

N

3.3v Supply (1st)

E6 Ctrl

25

V_3.3

3.3

N

3.3v Supply (1st)

E6 Ctrl

26

V_5.0

5.0



USB VIN, Always powered

27

IOC

3.3

L

Enable OLED Bias (2nd)

Always powered

28

IOD

3.3

M

Enable 2.8v Supply (1st)

Always powered

29

-





30

GND





31

DSI0_D0


D



32

DSI0_D0


D



33

GND





34

DSI0_D1





35

DSI0_D1





36

GND





37

DSI0_C


C



38

DSI0_C


C



39

GND





40

DSI0_D2





41

DSI0_D2





42

GND





43

DSI0_D3





44

DSI0_D3





45

GND





46

DSI1_D0


B



47

DSI1_D0


B



48

GND





49

DSI1_D1





50

DSI1_D1





51

GND





52

DSI1_C


A



53

DSI1_C


A



54

GND





55

DSI1_D2





56

DSI1_D2





57

GND





58

DSI1_D3





59

DSI1_D3





60

GND






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