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Doubts regarding Display Interfaces

Tony Philip , 04-29-2020, 01:46 AM
For a project, we are using a SOM with a display to go along with it (7" with Cap Touch). The SOM Supports, HDMI, eDP, MIPI communication directly via dedicated connectors .we are currently trying to figure out which display protocol ( HDMI, MIPI, eDP) is the best to go forward with. One Issue we currently have is that we lack experienced software programmers who have experience writing drivers for Displays.

I also had one observation and some questions: From our conversation with some Display vendors for MIPI DIsplays,I was told that OS drivers are not provided by manufacturers and vendors; but are to be written by end-user. [meaning, we have to write our own drivers ].
  1. Q : Is the above observation correct, or are we being misled by the vendors? Do you have more opinions on the above observation?
  2. Q : Also, is there any easy way in developing drivers for the MIPI display we intend to use?? (Use use Android OS)
  3. Q : Does eDP require different drivers for different displays (or does it work like HDMI, one driver for all displays) ??
  4. Q : What is the general approach taken to narrow down on what display communication protocol to use in embedded applications? (among eDP, HDMI,MIPI)
robertferanec , 05-01-2020, 01:08 AM
Generally, you should not need to write your own display driver if you are using one of the standard OS systems (e.g. Linux, Android, etc)

Usually display drivers only require configuration. So, when you download the SOM OS source code, look for the parts where they configure displays and go through the code. Depends on OS, often the configuration can be found in custom codes which are written for specific board (this custom board code is called BSP - Board Support Package). So you do not have to search through the whole source code, just go through the codes which were written specifically for your SOM and its reference development board. Then add support for your display or if you are not sure how to do it, edit an existing one.

PS: HDMI usually just works (depends if they require to read display information through DDC). If you are connecting display panel, then you may need to be more specific e.g. you may need to specify size, frequency, dataformat etc.

Hope this helps.
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