When working with dot matrix screens, the most challenging part is usually the interface circuit. Compared to a backlight circuit, which is quite simple and typically requires only three lines (power, ground, and backlight control signal), the screen interface can be much more complex. Most of these circuits operate at a high level, so you don’t need to worry about brightness adjustment—just make sure the power, ground, and turn-on signals are properly connected.
LVDS interfaces, for example, were developed from TTL technology. Let’s take a single six-bit TTL interface as an example. This type of interface typically requires at least 20 lines. In addition to power and ground, there are three primary color signal lines: R0–R5, G0–G5, B0–B5. Then there are synchronization signals like HS, VS, DE (data enable), and CLK (clock). With so many lines, it's easy to get interference, which is why this type of interface isn't used as often anymore. Most modern LCDs today use LVDS instead.
LVDS operates at a low voltage, around 1V, and is usually a single row. Common pin counts are 20 or 30 pins. The data is transmitted in pairs, which helps reduce noise and improve signal integrity.
Common configurations include single 6-bit (D6L or SI6L), single 8-bit (D8L or SI8L), double 6-bit (S6L or D06L), and double 8-bit (S8L or D08L). These designations refer to how many bits of data are sent per pixel and whether it's a single or dual channel.
The power supply voltage for the screen is generally 3.3V, 5V, or 12V. For example, 15-inch and smaller screens usually run on 3.3V, while 17–24 inch screens commonly use 5V. For 26-inch and larger screens, 12V is typical, though there are exceptions. It’s important not to try connecting a 12V screen to a 5V power source unless you're certain it's compatible. Doing so could damage the screen or the board.
To determine whether a screen uses a single 6-bit, single 8-bit, double 6-bit, or double 8-bit configuration, you can look at the number of twisted pairs in the cable. A single 6-bit interface has 4 pairs, a single 8-bit has 5 pairs, a double 6-bit has 8 pairs, and a double 8-bit has 10 pairs. Each pair carries either data or clock signals. For example, a single 6-bit interface has 3 data pairs and 1 clock pair, while a single 8-bit has 4 data pairs and 1 clock pair.
In practice, most people prefer to stock 8-bit cables because they can be adapted to 6-bit by removing one pair. However, converting a 6-bit to an 8-bit is more complicated. If you don’t have the right cable, you should try to find a suitable replacement. The order of conversion is usually double 8 → double 6 → single 8 → single 6. Always pay attention to the pin positions, as misalignment can cause serious issues. Most boards have markings to help identify the correct connections.
If the original cable is a flat ribbon cable, you can also check the logic board for clues. Power lines are usually connected through a fuse resistor, and the ground is typically connected to a large copper area. Data and clock lines are usually adjacent and go into the chip through small resistors. Each pair of data or clock lines usually has a 100Ω resistor nearby. By counting the small resistors connected to the screen interface, you can estimate the bit width of the display.
Understanding the interface is just the first step. You also need to know how the data lines, ground, and power are connected. It's important to figure out the screen resolution and size. While resolution is crucial, screen size isn't always that critical.
Once the screen cable is correctly connected, the motherboard should recognize the resolution and power settings, allowing the screen to light up. However, even if the screen turns on, the program might still not work properly. You may need to adjust settings such as character display, button functions, or other configurations. If things still don’t work, consider changing the firmware or software.
This is my personal experience and understanding. I hope it helps others, and I welcome any corrections or suggestions from more experienced peers. Substation Structures,Telegraph Pole,Substation Steel,Substation Steel Structures JIANGSU HONGGUANG STEEL POLE CO., LTD. , https://www.hgsteelpoles.com