AM62, USB enumeration to detect legacy power source, (USB2.0, 3.0, BC.1.2)

Technical Support
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1

Hi Toradex,

I am using AM62 and designing the carrier board, would like to ask if it is ok to connect a Legacy power source to USB-C sink (which is my custom-made carrier board). I’m wondering if my carrier board (which needs min. 5W power) could be able to power up by a Legacy source without an issue?

  1. From Adding USB-C to your Carrier Board Design - Part 1, saying that if the carrier board is connecting to the type-A connector( e.g. USB power source adpator) which is a USB BC1.2 power mode the “…Presence detection of battery charger host by measuring the resistance between D+ and D- lines of USB 2.0 Signals​…”. May I ask if the USB host on AM62 supports this feature?

  2. also if the power source is a default USB 2.0/3.0 “…USB enumeration is required over USB signals. Without enumeration, only 150 mA is allowed​…”. Any the additional SW configuration I need to follow?

thx
Andy

2

ould you please specify exactly which “Legacy source” you are referring to? According to the USB 2.0 specification, hosts can deliver 5V at 500 mA, for a total power output of 2.5 watts . USB 3.0 and 3.1 specifications permit 5V at 900 mA, resulting in 4.5 watts of power. The 2.5 watts may not be sufficient to power any Verdin AM62 module, whereas 4.5 watts are adequate for some variants of the Verdin AM62 modules.

However, for USB enumeration to occur, the module needs to be up and running, which is nearly impossible to achieve on a 0.75-watt budget.

3

Legacy source is mentioned in the web and I crop here for reference:

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Yes, I agreed with u that USB2.0 may not have enough power for AM62.

How about a scenario: the USB3.x power source to a standard-A plug to type-C receptacle, Does it means a USB enumeration is necessary before the source can fully output its power(0.9A)?

thx
Andy

4

Many (if not all) USB wall adapters can deliver 1-2 amps without negotiation, so using this type of power source should be sufficient. However, the vast majority of USB host implementations on laptops and desktop computers adhere to the USB specification and will not provide more than 150mA without negotiation. Although it is possible to boot a Verdin AM62 in a low-power mode and proceed with proper USB enumeration, this functionality is not currently implemented and would require significant modifications to the bootloader.