STUSB1602 SPI interface

[Lukasz Przenioslo]

Hello there,

I am currently analyzing the STUSB1602 chip and the P-NUCLEO-USB002 eval kit. I have come across a topic I am not fully certain about. Its the SPI interface for the BMC communication. I cannot understand either it is necessary in all applications, or only if I want to exchange some specific data between devices over CC line? For example, if I intend to create a sink only device, so I have to connect the SPI lines and provide any data from the MCU? I would appreciate all help.

[Benoit FORET]

Hi Lukasz,

to get a confirmation, please try "p 1" command. It will print the SOURCE PDO. I have seen a few phones able to SOURCE​ 9V, but so far no laptop that can do it. To do so, there is an Hardware cost, and there a quite a lot of USB port still on a laptop (so cost duplicated). I think laptops' main use case is still HDD or USB key connection.

rgds,

Benoit

[Lukasz Przenioslo]

Hi Benoit, thanks for answer.

I will be able to confirm this tomorrow, as today I dont have access to the PC.

In general I agree with you. Taking under consideration how expensive are the end game mobile workstations, adding an additional DC-DC converter in order to allow higher sourcing voltages over USB C would not hurt... Imagine how convenient it would be to connect a 3.5' HDD over USB C converter without additional cables (12V needed)...

[Lukasz Przenioslo]

Hello Benoit,

I have assembled the STEVAL-ISC004V1 with nucleo board in order to be able to use the gui. I now connected the boards like this to the PC using both USB C ports:

In this video I show the results in the GUI app:

https://youtu.be/eYHHfcFV3rs

It seems like the contract is accepted, but then it disappears? Also, does it really agree for PDO 5 for a sec? In the video I try both USB C ports on the Dell 7730 unit.

[Benoit FORET]

​Hi Lukasz,

the connection looks good. But the behaviour is typical of STUSB4710 going into error recovery (fault condition => terminate connection => restart => re-negotiate => fault etc...) because VBUS voltage can't meet the agreed voltage (20V in your case) within the right amount of time defined by the standard (5V to 20V transition is less than 270 ms). You should monitor VBUS on the scope and check it meets the UVLO / OVLO threshold at 20V (18V/21.6V). Maybe you can try to enlarge the UVLO/OVLO to +/-20% to give more margin in case the power supply you use is weak. See the result with a 2018 HP EliteBook840 G5.

[Benoit FORET]

[Lukasz Przenioslo]

Benoit,

You are right, it was my bad- I have manually set the current limit to 100 mA on the AC adapter. After turning it up to 2A here is the result:

Nothing superior here though... Also the PC doesn't want to be charged. Seems like your PC is way better USB C wise- can you charge it from the STEVAL-ISC004V1?

[Benoit FORET]

What is your laptop' battery State Of Charge? I think bellow 20%, it will give an idea how the laptop charging algorithm behaves with a Universal Power supply (I mean non-DELL). I believe it may not charge at the fastest way, but charge anyway (close to 1.2A). As you can see, mine has several 15W profiles (Buck-boost inside) which make it quite universal, but this is half the original HP AC adapter. And yes, when battery is low, the laptop is sinking about 100mA less than the negotiated contract, which is a good implementation. Bye

[Lukasz Przenioslo]

The laptop was 80% SoC. I will then check at 20% and less, thanks.