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DS90C185: Working with ILI9881C and low power mode

Greg Girard1
Prodigy 90 points
Part Number: DS90C185

Hello,

This is my first time working with the DS90C185 and a DSI type interface.  I am reading more about DSI and trying to get the concept of low power mode.  I see when it boots up it it in low power mode or LP-11.  My question is, when in low power mode, the lanes are single ended rather then differential to be able to configure the device.  It keeps saying how to enter all these modes and what not but I am missing the very basic element here.  How do I make it from LP-11 to LP-10?  As in, what do I have to send to the chip to have change the voltage when its in the single ended mode?  I know I am probably missing something simple but I don't see it.   

  • 0
    TI__Guru* 90880 points

    Hello Greg,

    Yes you are correct. In Low Power (LP) mode, the signaling is two single-ended with 1.2V swing operating at a maximum data rate of 10 Mb/s.
    The LP mode consists of four possible states: LP-00, LP-01, LP-10, and LP-11. 

    During normal operation a Data Lane will be either in Control or High-Speed mode. High-Speed Data transmission happens in bursts and starts from and ends at a Stop state (LP-11), which is by definition in Control mode. The Lane is only in High-Speed mode during Data bursts. The sequence to enter High-Speed mode is: LP-11, LP-01, LP-00 at which point the Data Lane remains in High-Speed mode until a LP-11 is received.

    The LP to HS transition happens for every MIPI long packet (line packet) during video transmission automatically. The default configuration of the device will allow this without needing to program any registers once video becomes available at the device input.

    If you want more details please read the complete description in the MIPI D-PHY Specification document.

  • 0 in reply to Hamzeh Jaradat
    Prodigy 90 points

    Thanks for the response.  Just to clarify, the LP modes are done automatically so I don't have to do anything to influence this?  For example, if I wanted to enter escape mode it says I have to do LP-11->10->LP-00->LP-01->LP-00.  I have 24 data lines and the 4 control lines to influence the lanes along with the 4 controls for configuring the device.  Do I just have to send the 8 bit entry command on data lane 0 and do the clocking myself to do this?  Do you see what I am getting at on what I don't understand?   

  • +1 in reply to Greg Girard1
    TI__Guru* 90880 points

    Correct, you do not need to do anything. For each received long packet the MIPI signal will go automatically through these modes until it reaches High-speed mode. After the payload is finished, the lanes will go again into the LP-11 state without you doing any thing.