MIPI DSI DCS Long

[idlacrosseplayer]

Hey everyone,

I have a MIPI DSI display that requires DCS to do some setup, however, they use a DCS LONG command to change to another "page" of DCS commands for their vendor specific setup. After doing some vendor specific stuff, the swap back to page-0 (another DCS Long) and continue with standard DCS shorts.

I see in the User Guide, that Xilinx only supports DCS shorts. Is there a way to either get LONG commands supported, or maybe "trick" the device into several SHORT writes? I tried to send several generic short writes instead of DCS short writes.

Also, what are the differences between sending a DCS short write and a GENERIC short write, other than the command opcode?

[karnanl]

Hello @idlacrosseplayer

Short answer:

DCS long write commands are not supported. Please check this Answer record:
https://www.xilinx.com/support/answers/71336.html

--More explanation will be added in next version of PG238. (will be released around 2018.3)

BTW, could you please check Xilinx PG238 ? We already mentioned that our MIPI DSI-2 IP only support Type4 arc.

(See pictures below )

>Is there a way to either get LONG commands supported, or maybe "trick" the device into several SHORT writes?

Unfortunately, there is no workaround for this. We cannot guarantee/control the DCS short command output timing.

We do aware that there are some display features that can only be accessed through DCS long commands.

 I will file an internal request to notify developer team that we had request from customer to enhance our MIPI DSI TX IP. But, please understand that there is no fixed milestone for now.

Thanks & regards

Leo

[idlacrosseplayer]

Hi @karnanl

Thanks for the response! I am using this DSI Transmitter userguide: Here

https://www.xilinx.com/support/answers/71336.html says that we *can* do DCS reads, but the User Guide doesn't show it in the command list. Can I, in fact, do DCS reads?

Could you also help with the difference between DCS writes (0x05 and 0x15) and GENERIC (0x03, 0x13, 0x23) writes?

[karnanl · Accepted solution]

Hello @idlacrosseplayer

>Can I, in fact, do DCS reads?

No, you can't. Xilinx MIPI DSI TX IP does not support DCS read because we do not use bi-directional I/O.

Thank you for letting me know. I will fix AR#71336 (https://www.xilinx.com/support/answers/71336.html)

>Could you also help with the difference between DCS writes (0x05 and 0x15) and GENERIC (0x03, 0x13, 0x23) writes?

This question is regarding MIPI DSI spec. Suggest you to download the following docs from MIPI.org

   MIPI DSI specification

   MIPI Display Command Set specification

From MIPI DSI TX perspective, there is no difference. We just sent the same 4 bytes short packet with different data type. Generic Short write is vendor specific, so you can write whatever you want in byte2 and byte3, as long as your Display can interpret this packet. In the other hands, the DCS command should follow "MIPI Display Command Set specification".

Thanks & regards

Leo