Change PDO3 to 15V, 1.5A don't work

[LEGLAUDE]

Hello Everybody,

I'm new in this place.

I use an Evalboard ISC005V1 with STUSB4500 and an dedicate MCU to manage I²C port. I wanted to change the configuration of the PDO3 from 20V to 15V.

I select PORT3 ( write 3 in 0x70 register )

I configure DPM_REQ_RDO3 register ( adress 0x91 )  with 0x96, 0xB0, 0x04 and 0x00.

I soft reset the STUS4500 

But nothing change. VBUS and PDO3 out still 20V???

What's wrong

Thanks for the help!

[MiBA]

hi 

The registers you are looking for are not directly controling sink request , 
the link here could give you an example on how to do specific request with STUSB4500

https://www.st.com/en/embedded-software/stsw-stusb003.html 
I hope you will find here resources 

by default STUSB4500 algo is choosing the best power from his PDO so if your Sink PDO contain 15V & 20V 

the 20V will be choosen 

the register 70 modify only the number of available PDO it will not force Renegociation 

do do so you need to send soft reset message 

behavior is 
- modify number of PDO to have only 2 available PDO 5V , 15V 
- send soft reset message ( see the link )
> STUSB4500 will choose 15V then  

BR