DLPC3433: Setup for Qualcomm DSI host

Hi Arthur

I can get the DSI waveform as shown in the guide. However, the DLPC3433 seems not receiving any video signal.

Where can I find some sure timing parameters as in the example in the debugging guide?

My case is quite the same with Mr. Wladimir in the original post (ie. 1280x720, RGB888, 4 lanes, 60fps)

Regards,

Huy

Hi Huy,

Welcome back to TI E2E forums.

We'll get back to you within the next few days.

Thanks,

Lori

Hi Huy,

Can you list the steps you are taking to set up DSI on your DLPC3433 system ? Please include steps to setup hardware, steps to setup DSI output from DSI controller, and i2c commands sent to DLPC to setup DLPC3433 for DSI input.

Please also review the DLPC3433 software programmer's guide to ensure the i2c commands you are sending are correctly formatted: https://www.ti.com/lit/ug/dlpu020d/dlpu020d.pdf 

Thank you,

Chris

Hi Chris,

1. Hardware setup: it 's quite similar with your recommend setup in the datasheet of DLPC3433, included DLPC3433+DLPA200+DLP3010. I am useing atxmega to send I2C command to the DLPC3433. I uploaded the firmware downloaded from your Firmware Selector page, and can see the splash image. Now I am trying to input DSI video signal from a Qualcomm Dragonboard to DLPC3433.

2. DSI output setup: I needed to edit the kernel (the device tree) and added a dsi config file. The parameters used for the config file are taken from the spreadsheet provided by Qualcomm. Below is the parameters I referred from the original question

• bpp = 24 (RGB888)
• 4 lanes
• width = 1280
• height = 720
• hfp = 112
• hbp = 220
• h-pulse-width = 40
• vbp =  20
• vfp = 5
• v-pulse-width = 5
• framerate = 60
• This is calculated as a PixClk of 74.34Mhz and bitclk=446MHz, this means DLPC3433's HS clock=223MHz
• Following the guide lines I set qcom,mdss-dsi-bllp-eof-power-mode, and qcom,mdss-dsi-bllp-power-mode, qcom,mdss-dsi-force-clk-lane-hs, qcom,mdss-dsi-always-on, qcom,mdss-dsi-tx-eot-append (for enabling EOT mode?), qcom,panel-ack-disabled (for disabling BTA mode?)

Other timing setting:

• T_HS_PREPARE=71ns,
• T_HS_ZERO=430ns
• T_HS_TRAIL=71ns
• T_HS_EXIT=233ns
• T_CLK_PREPARE=89ns
• T_CLK_ZERO=430ns
• T_CLK_TRAIL=71ns
• T_TA_GO=260ns
• T_CLK_POST=304ns
• T_CLK_PRE=37ns

I confirmed the output DSI signal by an oscilloscope. The waveform shows HSYNC, VSYNC, HFP, HBP widths quite corresponding to set parameter. However I'm not sure about the timings such as T_HS_PREPARE, T_HS_ZERO...

3. I2C command: I followed the guide in my first post:

• set DSI post enable
• set display size 1280x720
• set input image size 1280x720
• set HS clock: 223MHz
• select input source to External Video
• select External Video source format: auto dectect

Please tell me if I am doing anything wrong.

Thank you.

Huy

Hi Huy,

The steps you are following are correct. Please also ensure the following:

• Ensure that your hardware set-up follows the DLPC3433 datasheet on DSI input data and clock (section 5.3 of datasheet: https://www.ti.com/lit/ds/symlink/dlpc3433.pdf. Of particular interest is ensuring that your RREF is set up correctly, and that you have configured the DLPC3433 for 4-lane DSI input. 
• Ensure that the DSI host timing requirements are within specification (section 6.15 of datasheet)
• Ensure that the DLPC3433 is set up to receive DSI (point #3 of your post) BEFORE DSI is being output from your host processor

Let me know if this solves the issue, or if there is clarification needed.

Thank you,

Chris 

Hi Chris,

Thank you for your advice. 

I checked these 3 points, and these seem OK. But the DLPC3433 still does not receive any signal.

Could you please confirm that my above DSI setup parameters are OK?

Or could you please suggest reference parameters for this case?

Thank you,

Huy

Hello Huy,

Our team will look into your request and will give you an update in a couple of days. 

Regards,

Mayank

Hi Huy,

Can you try these paramters:

• bpp = 18 (RGB565)
• 4 lanes
• width = 1280
• height = 720
• hfp = 10
• hbp = 7
• h-pulse-width = 3
• vbp =  7
• vfp = 4
• v-pulse-width = 3
• framerate = 64
• pclk = 61582800

Can you use this worksheet to calculate the DSI HS clock ?7167.DSI-HSClock.xlsx

Thank you

Chris