DS90UH947-Q1: UH947 to UH928 i2c communication lock-up

William Taylor

Prodigy 90 points

Part Number: DS90UH947-Q1

Tool/software:

Hi at TI, I have a 947 to 928 communication issue.

I can talk via i2c from the 947 to a screen with the 928.

I can reach the remote devices in the screen no problem(microcontroller and touch controller)

I can read local registers(0x5A) that tell me the link is in the single TX mode as expected so not problem.

All this time there is no Oldi input to the 947.

As soon as I turn the video on(Dual Oldi) to the 947.

For and instant I can see from 0x5A that the link is ready, TX active and RX locked, still single TX on port0, and Oldi flags good.

Then next read of that register shows link not ready, and back to dual TX mode, the default setting.

Anyone got any thoughts on this - plainly I am doing something wrong.

Thanks in advance for any suggestions

William

1 month ago

0 Jack Scherlag 1 month ago

TI__Mastermind 20575 points

Hi William,

Thank you for including the background of your issue. When interfacing the 947 with the 928, it is important to note that there is a max PCLK difference. The 947 can support a max PCLK of 96MHz on a single link while the 928 only supports up to 85MHz on a single link.

What is the PCLK of your display?

William Taylor said:
Then next read of that register shows link not ready, and back to dual TX mode, the default setting.

The 947 supports dual link while the 928 does not. I recommend forcing the 947 to single link mode via register 0x5B (DUAL_CTL1).

Best,

Jack

0 William Taylor 1 month ago in reply to Jack Scherlag

Prodigy 90 points

Hey Jack, thanks for getting back to me, I will give that a shot today and let you know how it goes.

Dual Oldi Pclk is 34.5MHz so 69 over the single link shouldn't be an issue.

Thanks again

William

0 Jack Scherlag 1 month ago in reply to William Taylor

TI__Mastermind 20575 points

Hi William,

Keep me updated. I also want to point out the requirements listed in Section 9. After power up, there are additional register writes required for the OLDI block.

Best,

Jack

0 William Taylor 1 month ago in reply to Jack Scherlag

Prodigy 90 points

Thanks Jack for the extra info. and yes we are doing that.

To confirm too, forcing the link works and the system is happy.

Thanks again Jack.

William

Interface

Interface forum

DS90UH947-Q1: UH947 to UH928 i2c communication lock-up