How to connect an HDMI to LVDS adapter to a point-of-sale system
To connect an HDMI to LVDS adapter to a point-of-sale system, you first need to verify that the adapter supports the specific LVDS interface your POS display panel uses, typically a 30-pin or 40-pin connector with a defined voltage level (3.3V or 5V). Most POS systems, like those from Epson, Star Micronics, or NCR, output HDMI video signals from their mainboard, but the display panel inside the unit often runs on LVDS (Low-Voltage Differential Signaling) because it reduces electromagnetic interference and supports longer cable runs within the chassis. You’ll physically connect the HDMI output from the POS system’s board to the input of the hdmi to lvds display adapter, then wire the adapter’s LVDS output to the panel’s ribbon cable, matching pin assignments for power, ground, clock, and data pairs. For example, a typical 30-pin LVDS connector uses pins 1-4 for power, 5-6 for ground, and pairs 7-12 for data channels, but this varies by manufacturer. You must also supply 12V or 5V DC power to the adapter board, depending on its spec sheet, often from the POS system’s internal power supply or a separate adapter. Some POS boards, like the Logic Controls LCP-2000 series, have a dedicated LVDS header, but if yours lacks one, this adapter bridges the gap, converting HDMI to LVDS without needing a firmware update. The key is to check the panel’s datasheet for resolution support—most adapters handle 1366x768 or 1920x1080 at 60Hz—and ensure the POS system’s GPU can output that resolution over HDMI. If the screen stays black, you likely have a pin mismatch or voltage issue, so use a multimeter to confirm 3.3V on the LVDS power pins before powering up.
Understanding the HDMI to LVDS adapter hardware
These adapters are small PCBs, typically measuring 60mm x 40mm, with an HDMI female port on one side and a 30-pin or 40-pin LVDS connector on the other. The chipset inside, often from Realtek or T.I., handles the protocol conversion, decoding HDMI’s TMDS signals into parallel LVDS data. For POS systems, the adapter must support EDID emulation, meaning it tells the HDMI source (the POS board) that a display is connected, even if the panel isn’t powered yet. Without this, the POS system might disable its HDMI output, causing no signal. Data from hdmi to lvds display adapter spec sheets shows that most adapters support 6-bit or 8-bit color depth, which affects how many shades of gray the panel can display—critical for POS systems showing barcode scans or receipt previews. The LVDS interface itself uses four differential data pairs (channels 0-3) plus a clock pair, each running at about 85 MHz for 1080p, with a total bandwidth of roughly 1.6 Gbps. If your POS panel is a 1366x768 resolution, the data rate drops to around 600 Mbps, reducing power consumption by 20-30% compared to 1080p. The adapter’s power input is usually a 2-pin header or barrel jack, accepting 5V to 12V DC, and it draws about 0.5A to 1A depending on the panel size. For example, a 15-inch POS panel with 1024x768 resolution might draw 0.6A at 5V, while a 21.5-inch 1080p panel could pull 1.2A at 12V. Always check the adapter’s maximum current rating; exceeding it can fry the voltage regulator, which is often a AMS1117-3.3 chip rated for 1A. You can verify this by looking at the chip’s marking on the board—if it says “1117-3.3,” it’s for 3.3V output, common for 30-pin LVDS. For 40-pin panels, the adapter might use a separate 5V rail, requiring a jumper setting on the board.
Identifying the POS system’s LVDS panel interface
Every POS display panel has a specific connector and pinout, documented in its datasheet or on the panel’s label. For example, a common panel like the AU Optronics B150XW02 V0 uses a 30-pin LVDS connector with a 3.3V power supply, while the LG LP156WH2 uses a 40-pin connector at 5V. To find this, remove the panel from the POS chassis—usually by unscrewing four screws around the bezel—and look for a sticker on the back of the LCD glass. The sticker might say “M150XW01 V8” or “N140BGE-L41,” which you can search online for the pinout diagram. If the sticker is missing, count the pins on the ribbon cable connector: 30-pin connectors are common for 15.6-inch panels, while 40-pin ones are used for 17.3-inch or larger. The LVDS signal itself uses differential pairs, meaning each data channel has a positive and negative wire (e.g., RX0+ and RX0-), which you must match exactly to the adapter’s output. A mismatch can cause a garbled display or no image at all. For instance, if the adapter outputs data on channel 0 but the panel expects it on channel 1, you’ll see vertical lines or a scrambled screen. Some POS systems, like the Touch Dynamic 15-inch model, use a proprietary LVDS pinout, so you might need to rewire the adapter’s cable by cutting and splicing wires. Use a crimp tool and 0.5mm pitch connectors for 30-pin, or 0.4mm for 40-pin, to avoid shorts. The voltage level is critical: 3.3V panels can be damaged by 5V input, so measure the panel’s VCC pin with a multimeter before connecting. If the panel’s datasheet isn’t available, assume 3.3V for 30-pin and 5V for 40-pin, but verify with the POS system’s service manual. For example, the Epson TM-T88V’s internal display uses a 5V 30-pin LVDS, while the Star SP700’s panel runs at 3.3V. You can also check the POS system’s mainboard for a jumper labeled “LVDS_VOLT” or “VCC_SEL” that sets the voltage, often near the LVDS header. If present, set it to match the panel, or the adapter might not power up correctly.
Power supply considerations for the adapter
The HDMI to LVDS adapter needs a stable DC power source, typically 5V or 12V, and drawing this from the POS system’s internal PSU is common. Most POS systems have a 12V rail that can supply up to 5A, enough for the adapter and panel combined. For example, a typical POS system like the NCR 7456 uses a 150W power supply with a 12V output at 8A, so you can tap into this by soldering wires to the PSU’s output terminals or using a SATA power splitter. The adapter’s power consumption is low: around 0.5W for the chipset plus 3-5W for the panel backlight, totaling 4-6W for a 15-inch panel. If you use a separate power adapter, choose one with at least 1A output at 5V or 12V, and a 2.1mm barrel jack with center positive polarity. The adapter’s datasheet typically specifies the voltage range; for example, the RTD2660-based adapters accept 5-12V, but the voltage regulator gets hot if you run 12V for extended periods. Measure the temperature with a thermocouple after 30 minutes of operation—if it exceeds 85°C, add a small heatsink (10mm x 10mm) to the regulator chip. The backlight power is separate from the LVDS data; most panels use an LED backlight that requires 3.3V or 5V at 200-400mA, controlled by the adapter’s inverter or a separate LED driver board. If your panel doesn’t light up, check the backlight enable pin on the LVDS connector, which is often pin 14 on 30-pin JAE connectors. This pin should be pulled high (3.3V) by the adapter; if not, you can connect it to the adapter’s 3.3V output through a 10k resistor. Some adapters have a jumper for backlight voltage selection, labeled “BL_VOLT,” set to 3.3V or 5V based on the panel. For example, the Samsung LTN140AT01 panel needs 5V for backlight, while the Chi Mei N140BGE-L41 uses 3.3V. Get this wrong, and the backlight might be dim or flicker.
Wiring the LVDS cable between adapter and panel
The LVDS cable is a flat ribbon cable with a specific pitch, usually 0.5mm for 30-pin or 0.4mm for 40-pin connectors, and you must match the pin-to-pin mapping exactly. Start by cutting the cable to length, typically 10-15 cm, to avoid signal loss over longer runs. Use a wire stripper to expose 2mm of each conductor, then tin them with solder to prevent fraying. The adapter’s output connector is often a JAE FI-SE series or Hirose DF13, with pins labeled 1-30 or 1-40. The panel’s input connector is similar, but the pinout order might be reversed. For example, on a 30-pin connector, pin 1 is often the power supply (VCC), pin 2 is ground (GND), pins 3-6 are data channel 0 (RX0+, RX0-, RX1+, RX1-), and so on. The clock pair is usually pins 7-8 (CLK+, CLK-). If you wire the data pairs in reverse order (e.g., RX0+ to RX0-), the display will show a negative image or no signal. Use a multimeter in continuity mode to verify each connection before plugging in. For a 40-pin connector, the pinout is similar but with additional data channels for higher resolutions. For instance, a 1080p panel uses four data channels, so pins 1-4 are VCC, 5-6 are GND, 7-14 are data channels 0-3, and 15-16 are clock. Some panels also have a spare channel for 6-bit color, which you can leave unconnected if the adapter only supports 8-bit. The cable’s impedance is critical: LVDS requires 100-ohm differential impedance, so use a twisted-pair cable or a pre-made ribbon cable rated for LVDS. If you use a generic IDE cable, signal reflections can cause data errors, leading to pixel flickering. You can test this by running a pattern generator from the POS system; if you see “snow” or random dots, the cable impedance is off. Replace it with a cable that has a 100-ohm characteristic impedance, like those from 3M or Amphenol. The connector’s locking mechanism is also important: many POS panels use a latch-type connector, so press firmly until you hear a click. If the cable is loose, vibrations from the POS system’s fan can cause intermittent disconnects, which look like a blank screen or garbled text.
Configuring the adapter’s EDID and resolution settings
Most HDMI to LVDS adapters come with a default EDID (Extended Display Identification Data) that tells the POS system the panel’s native resolution, refresh rate, and timing. For example, a common EDID for a 1366x768 panel includes a horizontal active time of 1366 pixels, vertical active time of 768 lines, and a pixel clock of 72 MHz. If the POS system outputs a different resolution, like 1024x768, the adapter might scale it or fail to display. You can reprogram the EDID using a USB-to-I2C adapter, like the FTDI FT232H, by connecting to the adapter’s I2C bus (pins SDA and SCL on the board). The default EDID is stored in a 24C02 EEPROM chip, which you can read and write using software like EDID Editor or Phoenix EDID Designer. For example, if your POS panel is a 1280x800 resolution, you need to modify the EDID’s timing descriptor to match that resolution, with a horizontal sync width of 40 pixels, vertical sync width of 5 lines, and a refresh rate of 60Hz. Without this, the POS system might output a 1080p signal, which the panel can’t display, resulting in a blank screen or “out of range” message. Some adapters have a DIP switch or jumper for resolution selection, like “SW1” for 1366x768 and “SW2” for 1920x1080, which sets the EDID automatically. For example, the hdmi to lvds display adapter from DisplayModule has a 4-pin jumper block that lets you select between 6-bit and 8-bit color, and between 1366x768 and 1920x1080. If you set it to 1080p but the panel is 1366x768, the adapter will scale the image, but quality might be poor due to interpolation. The POS system’s GPU also plays a role: older Intel HD Graphics 2000 chipsets might not support 1920x1080 over HDMI, so check the system’s specs. For example, an NCR 7456 with a Celeron processor might only output 1366x768, so set the adapter accordingly. You can test the output by connecting a standard HDMI monitor first; if the POS system shows a desktop at 1366x768, the adapter should match that. If the screen is shifted or has black borders, adjust the horizontal and vertical position in the adapter’s OSD menu, if available, by pressing a button on the board (often labeled “MENU” or “UP”). Some adapters have a micro-USB port for firmware updates, which can fix EDID bugs or add support for unusual resolutions like 1280x1024, common in older POS panels.
Testing the connection and troubleshooting common issues
After wiring and powering up, the POS system should detect the panel as a standard HDMI monitor. If the screen is black, use a multimeter to check the LVDS connector’s power pin (VCC) against ground (GND)—it should read 3.3V or 5V, depending on the panel. If it’s 0V, the adapter isn’t powering the panel, so check the power input to the adapter. Next, measure the data pins: with an oscilloscope, you should see a differential signal of about 1.2V peak-to-peak on the clock pair. If you see a flat line, the adapter isn’t receiving HDMI data, so check the HDMI cable connection. A common issue is the POS system’s HDMI port not outputting a signal because it’s disabled in the BIOS. For example, on a Dell OptiPlex 3020 used as a POS, the HDMI port might be turned off if the system detects a VGA monitor. Enter the BIOS by pressing F2 during boot, then look for “Video Configuration” or “Primary Display” and set it to “HDMI” or “Auto.” If the POS system has a touchscreen controller, it might interfere with the video signal; disconnect the touch USB cable temporarily to isolate the issue. Another frequent problem is backlight failure: if the panel shows a faint image when you shine a flashlight on it, the backlight isn’t powering. Check the backlight enable pin on the LVDS connector (often pin 14 for 30-pin) with a multimeter—it should be 3.3V. If it’s 0V, the adapter isn’t enabling it, so you might need to pull it high with a 10k resistor to 3.3V. The backlight voltage pin (usually pin 15 or 16) should read 3.3V or 5V; if it’s 0V, the adapter’s voltage regulator might be faulty. For example, on a 30-pin panel, the backlight is powered by the same 3.3V rail, but some panels require a separate 5V line. If the image is garbled, the data pairs are likely swapped. For instance, if the red channel shows as blue, swap the RX0+ and RX0- wires, or swap the entire data channel pairs. You can test this by connecting the adapter to a known working panel; if the image is correct, the issue is with the POS panel’s pinout. If the screen flickers, the cable might be too long or the impedance mismatched; keep the cable under 20 cm and use twisted pairs. If the POS system’s GPU is overheating, it can cause signal dropouts; monitor the temperature with HWMonitor and add a heatsink if it exceeds 90°C. Finally, if the adapter itself gets hot (above 70°C), it might be drawing too much current from the panel, so check the panel’s power consumption—a 21.5-inch panel at 1080p can draw 1.5A, which might exceed the adapter’s regulator rating. In that case, use a separate power supply for the panel’s backlight, like a 12V LED driver board, and connect only the data signals from the adapter.
Integrating the adapter into the POS chassis
Once the adapter is working, you need to mount it inside the POS system’s chassis to prevent shorts and ensure airflow. Most POS systems have a metal frame with mounting holes, so use standoffs (6mm height