DS90UB940-Q1: Connect 940 and 925 and color display has some problem

Amelie Zheng

Genius 10865 points

Part Number: DS90UB940-Q1

Hi Team,

My customer used 925 and 926 before, and have successfully make them work.

And now would like to change to use 925 and 940 but meet some issue. Here are the block diagram.

When they only use 940's pattern generation, the color bar could be showed in LCD but it is flicker.

When they use the external video source from 925 to 940 and then display in LCD. The video source is red, but the LCD display is very strange.

Here is the reg setting when 940 connected with 925.

Fullscreen 800_480_ds90ub940_configure.txt Download

ds90ub940_write_reg(0x6c, 0x13);
ds90ub940_write_reg(0x6d, 0xbf);

ds90ub940_write_reg(0x66, 0x03);
ds90ub940_write_reg(0x67, 0x06);

ds90ub940_write_reg(0x66, 0x07);
ds90ub940_write_reg(0x67, 0x20);

ds90ub940_write_reg(0x66, 0x08);
ds90ub940_write_reg(0x67, 0x03);

ds90ub940_write_reg(0x66, 0x1e);
ds90ub940_write_reg(0x67, 0x09);

ds90ub940_write_reg(0x66, 0x04);
ds90ub940_write_reg(0x67, 0x98);

ds90ub940_write_reg(0x66, 0x05);
ds90ub940_write_reg(0x67, 0xd4);

ds90ub940_write_reg(0x66, 0x06);
ds90ub940_write_reg(0x67, 0x20);

ds90ub940_write_reg(0x66, 0x0c);
ds90ub940_write_reg(0x67, 0xd8);

ds90ub940_write_reg(0x66, 0x08);
ds90ub940_write_reg(0x67, 0x23);

/*Program the output CSI data formats yuv422*/
ds90ub940_write_reg(0x6b, 0x50);

ds90ub940_write_reg(0x65, 0x04);  //color bar ok
ds90ub940_write_reg(0x64, 0x55);  //color bar ok

And as for 940, customer use the 940 EVM. Could you please give some advice?

Thanks!

over 5 years ago

0 Steven(Shenzhen) Shi over 5 years ago

TI__Mastermind 30515 points

hellow,

from the description, it could have two issues here, pls resolve it step by step:

1. the CSI2 port: this sounds not to work well, and could introduce many "strange" issue. as you can see, it has flicking, it means the connection between 940 and the following chip has issue, this must be resolved. the option is to make sure the MIPI data lane and clock lane have good impedance control (100ohms) and same length

2. after you resolve the 1st issue, if the display still has question, please check the video timing in your case is the standard CESA or not? if not, please follow up the timing setting requirement in the app. note http://www.ti.com/lit/an/snla303/snla303.pdf?ts=1588049796096

regards,

Steven

0 user5977425 over 5 years ago in reply to Steven(Shenzhen) Shi

Prodigy 20 points

Hi Steven:

Thanks for your reply, We will check the problem as you said.
Another question is the color bar displayed normally, but the external video cannot be captured normally. Do I need to configure any registers to achieve this?

Best regards

0 Steven(Shenzhen) Shi over 5 years ago in reply to user5977425

TI__Mastermind 30515 points

no special request, you also can use the mode_sel pin as default strap setting.

best regards,

Steven

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DS90UB940-Q1: Connect 940 and 925 and color display has some problem