topic Re: Change PWM value of PTN3356 through Linux PC in Digital Signal Controllers

Change PWM value of PTN3460I through Linux PC

tommys — Mon, 13 Sep 2021 11:34:23 GMT

Hello,

We would like to change the PWM value of PTN3460I from a Linux PC through Display Port. We expected the PTN3460I to be recognized by the PC as an I2C(I2C-over-AUX) device (slave address 0xC0) but could not find the slave address. Is it correct to access via AUX-CH(DPCD) instead of I2C? The EDID could be read at the slave address 0x50. Please tell us the correct access method.

Thank you for your cooperation.

Best regards,
tommys

Re: Change PWM value of PTN3356 through Linux PC

TomasVaverka — Sun, 12 Sep 2021 15:04:00 GMT

Hi Tommy,

Yes, you will have to to access via AUX-CH (DPCD register) instead of I2C if you want to change the PWM value of PTN3460I from a Linux PC through DisplayPort.

You will need to change DPCD register 0X722 and 0x723 via DP AUX channel to modify display brightness according to eDP (Embedded DisplayPort) specification v1.3 in below figures.

Best regards,

Tomas

Re: Change PWM value of PTN3460I through Linux PC

tommys — Mon, 13 Sep 2021 11:33:48 GMT

Hello Tomas,

Thank you for the reply.

In case of PTN3460I, what are the maximum and minimum values of brightness? We think 0x1000 is 0% and 0x0000 is 100%. Is it correct?

Best regards,

Tommy

Re: Change PWM value of PTN3460I through Linux PC

TomasVaverka — Tue, 14 Sep 2021 02:04:05 GMT

Hello Tommy,

PTN3460I default PWM setting is 12 bit, so that the DPCD register 0x722/0x723 working range is 0x000 – 0xFFF.

0x000 means PWM duty cycle = 100%, so PWM = 3.3V. And 0xFFF means PWM duty cycle = 0%, so PWM = 0V.

Best regards,

Tomas

Re: Change PWM value of PTN3460I through Linux PC

tommys — Tue, 21 Sep 2021 11:50:14 GMT

Hello Tomas,

Thank you for your reply. I understand.

Best regards,
Tommy