LVDS display on Apalis evaluation board

Technical Support
, ,
1

I have problems with connecting the Toradex LVDS display to an Apalis iMX8QM on an Apalis evaluation board with Linux BSP 6.8 multimedia.

I connected the display to X13, changed JP2 and JP3 to 5 Volts, added the LVDS overlay to overlays.txt and included the LVDS output section to weston.ini.

The display remains blank with weston running on DVI/HDMI. The backlight works (changed intensity from Linux).

I identified the type of display and checked resolution, clock, timing with the overlay.

Any ideas why it is not working?

Thanks,
Florin

2

Hi, I’m the Toradex AI Assistant.

I might make mistakes. Our support team will step in if needed. If I answered your question, please tick the “Solution” checkbox. For follow-up questions to me, please use @ToradexAI in your post.

Did you like my answer? :+1: :-1:

Troubleshooting LVDS Display on Apalis iMX8QM

Based on your configuration, there are several areas to check for your LVDS display connection on the Apalis iMX8QM with the Evaluation Board.

Hardware Configuration Verification

First, confirm your hardware setup matches the Apalis iMX8 LVDS configuration(1). The Apalis iMX8 provides display signals over HDMI and LVDS, where LVDS1 can be used as two single-channel LVDS or one dual-channel LVDS(1).

For the Apalis Evaluation Board:

  • LVDS1 Connector: X13(1)
  • Device-Tree Node Reference: ldb2(1)
  • DRM Connector Name: LVDS-1(1)

Device Tree Overlay Configuration

Ensure you’re using the correct overlay for your display. Toradex provides pre-built overlays for LVDS displays(2). For the Apalis iMX8, you should use:

  • apalis-imx8_panel-cap-touch-10inch-lvds_overlay.dtbo (for 10.1" capacitive touch LVDS display)(2)
  • apalis-imx8_lvds_overlay.dtbo (generic LVDS overlay)(2)

Common Issues and Solutions

1. Data Mapping Configuration

A common issue with LVDS displays is incorrect data mapping. Based on community feedback, you may need to adjust the fsl,data-mapping property in your device tree overlay(3)(4):

  • Try changing from spwg to jeida or vice versa(3)(4)
  • Verify the fsl,data-width setting (typically 18 or 24 bits)(3)

2. Display Timing Parameters

Verify your display timing parameters match your panel’s datasheet specifications(4). Key parameters include:

  • clock-frequency
  • hactive and vactive (resolution)
  • hsync-len, vsync-len
  • hfront-porch, hback-porch
  • vfront-porch, vback-porch

3. Weston Configuration

Since you mentioned Weston is running on DVI/HDMI, ensure your weston.ini configuration properly addresses the LVDS output. The LVDS connector should be configured as LVDS-1(1).

Debugging Steps

  1. Check DRM Status: Use modetest to verify the LVDS connector is detected and active
  2. Verify Overlay Loading: Confirm your overlay is properly loaded by checking the device tree
  3. Test Different Data Mappings: Try both spwg and jeida data mapping configurations(3)(4)
  4. Validate Timing Parameters: Double-check all timing values against your display datasheet

Additional Considerations

The Apalis iMX8 supports EDID for LVDS displays, though the common use case is to hard-code the mode information in the device tree or panel driver(1). Make sure your custom overlay includes all necessary timing and configuration parameters for your specific display.

Best regards, Toradex AI Assistant.

3

Thanks for your help. I used the overlay for displays with two channels. I switched to the correct overlay, for the 10.1” LVDS display with one channel, and it works, including on weston.

Florin