I have a designed a custom carrier board for the AM69 SOM and generally my DSI display works fine running for a whole day with no issues, occasionally when I start the system the display flickers and continues to flicker for as long as the system is switched on, then when I restart the system if most often is OK. I have asked the software developers and can see nothing wrong with the configuration and since it stable for long periods of time I agree that it is unlikely (but not impossible) that it is a configuration problem. one thing I have noticed is that when I have a flickering display and I probe the DSI D0_N signal with my scope the flickering stops and the display is stable and remains stable after the probe is removed. the DSI signals are direct from the SOM to the display connector with only some EMI filters. (as in the Aquila development board).
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DSI Display Flickering Issue on Custom AM69 Carrier Board
Based on your description, this appears to be a signal integrity issue rather than a software configuration problem. The fact that probing the DSI D0_N signal stabilizes the display is a strong indicator of electrical characteristics affecting the MIPI DSI interface.
Analysis of Your Observations
The intermittent flickering that resolves when probing suggests:
- Signal integrity issues on the DSI differential pairs
- Impedance matching problems between the AM69 SOM and your display
- EMI/crosstalk affecting the high-speed DSI signals
The Aquila AM69 supports MIPI DSI output and is compatible with various DSI displays(1)(2). The Aquila Development Board provides a reference implementation for DSI connectivity(3)(4).
Recommended Investigation Steps
-
Signal Integrity Analysis
- Check impedance matching on your DSI traces
- Verify differential pair routing follows high-speed design guidelines
- Measure signal quality on all DSI lanes, not just D0_N
-
Hardware Design Review
- Compare your EMI filter implementation with the Aquila Development Board reference design(3)
- Verify proper ground plane continuity under DSI traces
- Check for potential crosstalk sources near DSI routing
-
Power Supply Analysis
- Monitor power supply stability during flickering episodes
- Check for voltage ripple on DSI-related power rails
- Verify proper decoupling capacitor placement
Debugging Approach
Since the issue is intermittent and hardware-related:
- Document the environmental conditions when flickering occurs
- Test with different display panels if available
- Consider adding termination resistors or adjusting EMI filter values
- Review your PCB stackup and trace impedance calculations
The fact that your system runs stable for extended periods suggests the basic connectivity and software configuration are correct, supporting your assessment that this is likely a hardware signal integrity issue.
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Hello @redwin1960,
We have seen intermittent or hardware dependent flickering on MIPI-DSI displays in the past.
Usually small adjustments to the timing parameters are needed to make sure the display runs well when using a new board.
I recommend that you try to incrementally adjust the back-porch, front-porch, and sync timings to get a consistently stable output.
Best Regards,
Bruno
Hi Bruno, I have asked our software people to look at doing this however they suggest it could turn out to be a lot of work with little hope of finding the correct parameters that would work with our displays. Do you have any advice on how this may be accomplished.
Best regards
Vince
Hello @redwin1960,
While this does take some work, as the display is almost in a working state this indicates the timings are not too far off from what they should be.
You can see an example where we were seeing flickering in an AM62 SoM while with other SoMs this flickering was not seen with the same timings: Making sure you're not a bot!
The best workflow would be to setup an environment to compile the device tree overlays locally, for faster iteration.
This is documented here: First Steps with Device Tree Overlays | Toradex Developer Center
Changing some of the parameters such as the pixel clock or some of the vertical blanking times are more likely to yield results if the problem is a whole screen flicker.
If the problem is more related to some horizontal sliding of the image, then tweaking horizontal blanking times may be warranted.
Best Regards,
Bruno