TPS65982: Changing PD parameters on the fly by using I2C

Sergii Makovetskyi

Part Number: TPS65982

Dear TPS65982 experts,

is it possible to change power delivery parameters during normal work mode (when IC already configured by TI util) via I2C, to limit or extend maximum output current for sourcing external load?

We have 2x usb-C PD ports and we need to limit current at 2nd port when 1st port is used for charging MacBook.

Best Regards,

Sergii

over 8 years ago

0 Eric Beljaars over 8 years ago

TI__Mastermind 36756 points

Hi Sergii,

You can actively change registers such as the Source Capabilities during run time if you have an EC in your system. The EC would be the I2C master and speak to the TPS65982 to access its registers. A full description of each register and its features can be found in the Host Interface Technical Reference Manual: www.ti.com/.../slvuan1a.pdf
We also have some example EC code available in the FW update over EC application note: www.ti.com/.../slva783a.pdf

Thank you,
Eric

0 Sergii Makovetskyi over 8 years ago in reply to Eric Beljaars

Intellectual 495 points

Hi Erik,
thanks a lot, we will check that and back to you.
--
Best regards,
Sergii

0 Alexander Chamara over 8 years ago in reply to Sergii Makovetskyi

Prodigy 120 points

Hi Erik,

I'm working with Sergii Makovetskyi and I'm trying to write new register value in runtime via I2C interface by STM32 MCU to PD chip. I need to change max current value in register 0x32. I can read all 31 bytes of this register. It works fine. But when I write new value and then read it back the values doesn't changed. Message I send through I2C has format as described in document you mention above. There is any write protection for registers? When I write new register value is it store in internal PD chip FLASH memory? Will this value restored after power OFF -> ON sequence ?

Thank you.

0 Eric Beljaars over 8 years ago in reply to Alexander Chamara

TI__Mastermind 36756 points

Hi Alexander,

When you change a register via I2C, the new information will be stored in RAM. When you power cycle the device, the device will reload the base configuration that you stored in the flash.
When updating the max current value in register 0x32, you will need to reset the port connection via a 4CC command. When the 82 then reconnects and renegotiates a PD contract, the new value you put in for Max Current should be there.

Thank you,
Eric

0 Alexander Chamara over 8 years ago in reply to Eric Beljaars

Prodigy 120 points

Eric,
What register should I use for 4CC command? What means number 82? How to get this value?

Thank you.

0 Eric Beljaars over 8 years ago in reply to Alexander Chamara

TI__Mastermind 36756 points

Hi Alexander,

You can use the DISC 4CC command to disconnect the connection and let the TPS65982 renegotiate.
I apologize for the confusion, I was referring to the TPS65982 when I said "82".

Thank you,
Eric

0 Alexander Chamara over 8 years ago in reply to Eric Beljaars

Prodigy 120 points

Hi Eric,

I've found that PD chip always add one extra byte at the beginning of 4CC replies (register 0x08). The value of this extra byte is 0x04. So, reply looks like "0x04 0x21 0x43 0x4D 0x44" if command was wrong and "0x04 0x0 0x0 0x0 0x0" if command was ok. Also I have to add additional space character in my request " DESC" to make it work. I'm' using logic analyzer to see the packages on I2C bus.

Is that behaviour correct? I didn't found such description in referenec manual.

Thanks in advance.

0 Matthew Serwinowski over 8 years ago in reply to Alexander Chamara

TI__Prodigy 10 points

Alexander,

The extra byte at the beginning of the I2C reply indicates the number of bytes in the actual response. So 0x04 means the response is 4 bytes long.

A 4 byte response of 0x0 is the response when a command is accepted. The other reply you're getting is the hex equivalent of !CMD (ASCII conversion). !CMD is the 'unrecognized command' response in the reference manual.

I'm not what "DESC" is, did you mean "DISC" requires an extra space?

Best,
Matt

0 Alexander Chamara over 8 years ago in reply to Matthew Serwinowski

Prodigy 120 points

Hi Matthew,

Thanks for reply. It's clear now.

0 Alexander Chamara over 8 years ago in reply to Alexander Chamara

Prodigy 120 points

Hi,

I wasn't able to set new PD contract by DISC command when some device conencted to this PD chip.

So, I need to configure max current value for 4 PDO's in 0x32 register . My host controller send new current value and DISC command (register 0x08) every 5 sec. After every DISC comman host read back 0x08 register and it's always cleared to 0. So, I assume that command was successfully processed but power consumption doesn't changed.

What can be wrong?

Thanks.

0 Eric Beljaars over 8 years ago in reply to Alexander Chamara

TI__Mastermind 36756 points

Hi Alexander,

You can try sending the Send Source Capabilities 4CC command so that the sink can re-select a new PDO after you have changed them in the 0x32 register. This would allow the device to change the voltage without having to disconnect. The 4CC command is SSrc.

Thank you,
Eric

0 Alexander Chamara over 8 years ago in reply to Eric Beljaars

Prodigy 120 points

Hi Eric,

Now it works.

Thank you.

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TPS65982: Changing PD parameters on the fly by using I2C