PTN3460 DDC I2C speed

[Maurer]

We connected a I2C touchscreen controller to the DDC I2C Master, so we can poll the touch events over the displayport. This works so far, but it could work faster (there is a visible delay). According to the datasheet the DDC I2C interface supports Fast-mode(400kbit/s), but the the DPCD register "I2C speed control capabilities bit map" (0x0000C) shows a maximum supported speed of 100Kbps (0x0F). Also trying to set the speed to 400Kbps on register "I2C speed control/status bit map" (0x00109) failed. Is the datasheet wrong or is there a way to set the DDC I2C to Fast-mode?

[JozefKozon]

Dear Simon,

I am not sure, if the statement of 400kbit/s is meant for DDC I2C interface. Please check a PTN3460 Firmware F6 release note attached. The DDC I2C is set from 50kHz to 100kHz from the previous F4 Firmware.

I have attached all the documents I have to the PTN3460 and to PTN3460I. Perhaps you will find further information there. If not, please let me know an I will contact an application engineer to clarify the DDC I2C maximum communication speed.

With Best Regards,

Jozef

[Maurer]

Hi Jozef, 
thanks you for your reply. I read it in the document "PTN3460 eDP to LVDS bridge IC product data sheet" https://www.nxp.com/docs/en/data-sheet/PTN3460.pdf 
Second page, last point of "2.3 LVDS transmitter features":

"DDC control for EDID ROM access – I2C-bus interface up to 400 kbit/s"

best regards,
Simon

[JozefKozon]

Hi Simon,

please see below an answer from the application engineer. He confirmed, that the DDC I2C interface cannot be set to 400kHz. I apologize for inconvenience.

DESCRIPTION

We can’t change DDC I2C speed to 400kHz, it is hard coded in the firmware which is not configurable for user.

With Best Regards,

Jozef

[Maurer]

Hi Jozef,
so is the datasheet wrong? Is this only a firmware issue or is it a hardware limitation? If it's just a firmware issue, will it be fixed in the future?

best regards,
Simon

[JozefKozon]

Hi Simon,

please see below an answer from the application engineer I have just received.

DESCRIPTION

It is firmware issue, but we don’t have plan (or timeline) to release new firmware currently.

With Best Regards,

Jozef