LVDS Adapter V2 + 10" LCD with Touchscreen

10" glossy screen LCD, 1024x600 px, 256K (18-bits) colors with integrated 2 points capacitive touchscreen with USB interface

- new LVDS board that has all required voltages for LCD, contains PIC controller that provides correct EDID information (like screen resolution, etc) over DDC/I2C interface and also can control LCD brightness in automatic (with help of ambient light sensor) or manual (over I2C bus) mode

- LVDS cable

- ambient light sensor (can be connected as a part of LVDS cable to LVDS board) for automatic LCD brightness control


Tested to work with:
- BeagleBoard
- BeagleBoard-xM
- PandaBoard

LVDS LCD panels are typically used for notebooks and have resolutions in the 800x600 and above range. Color depths is usually 24 bits (8 bits per color channel) or 18 bits per pixel (6 bits per color channel). These panels are widely available in eBay and notebook spare parts suppliers, so prices are pretty cheap. LVDS stands for Low-Voltage Differential Signals, and allows pretty long connection cable between LCD panel and controller due to differential signals. Below we will consider how to connect such panel to BeagleBoard/PandaBoard and others OMAP-based development boards.

LVDS interface transmits video information encoded inside serial channels. LCD panel with LVDS interface requires 4 or 5 serial channels, usually, referred as RXCLK+/- for clock signal, and RX0+/-, RX1+/-, RX2+/-, RX3+/- for data (pretty often you can find them denoted as D0+/- or Y0+/-, etc) . The most important thing is the bit assignments within the serial LVDS channels. Currently there are two common color depths in LVDS LCD panels, namely 18 bit and 24 bit. When connecting to 18 bit LCD there is a de-facto standard for the assignment of the color data bits on the LVDS serial data channels. For 24 bit LCDs there are two different formats (MSB and LSB) and it is important to know what your particular LCD panel expects. Some 24 bit LCD panels can be configured in either of the 2 formats which can be extremely useful, allowing you to design hardware that can dive either 18 bit or 24 bit LCDs with no hardware or software changes.

MSB (Most-Significant Bits are transferred in separate channel RX3) LCD panels expects the following data encoding inside serial channels:
RX0+/-: R0-R5,G0
RX1+/-: G1-G5,B0-B1
RX2+/-: B2-B5,VS,HS,DE
RX3+/-: R6-R7,G6-G7,B6-B7,GND

LSB (Least-Significant Bits are transferred in separate channel RX3) LCD panels expects the following data encoding inside serial channels:
RX0+/-: B4-B7,VS,HS,DE
RX1+/-: G3-G7,B2-B3
RX2+/-: R2-R7,G2
RX3+/-: R0,R1,G0,G1,B0,B1,GND

As you can see, 18-bits LSB panel can be connected to system with 24-bits LSB format, just by omitting data in RX3 channel. But you will see mess of colors on LCD if try to connect 18-bits panel to 24-bits MSB system.

Our v1 PCB was designed for 24-bits MSB panels. These panels are used mostly by very expensive industrial LCD panels. Next PCB (v2) we designed for 24-bits LSB and 18-bits panels, as they are used by most of cheap notebook panels.