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White boarding a RoadTest Review of The Microchip PoE to USB-C®︎ adapter

colporteur

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What are your expectations at connection point C?

 

I am considering pitching an application for the Microchip PoE to USB-CRegistered Power and Data Adapter RoadTest review. I completed a review of a PoE device, Raspberry Pi4B (4GB) plus POE Hat - Review and figured why not leverage the knowledge into another PoE review.

 

The drawing shows my preferred setup for the RoadTest, a Linux laptop interfacing through a PoE Injector communicating with a Raspberry Pi4B. The injector is a device I acquired to resolve an issue I discovered during the RoadTest Review The Road to Raspberry Pi4B/ PoE Hat RoadTest Review (PoE insight needed) . I want to avoid more purchases.

 

After reviewing the documentation I'm confused about my expectations at point C in the diagram. I was hoping a white board session with others might clarify my understanding. One of the opportunities I miss in my retirement is the napkin discussion with technical minds during a coffee break at work. Using a drawing scribbled on a napkin, like minds worked to offer insight into solving a problem presented at the table.

 

The Microchip PoE to USB-CRegistered Power and Data Adapter provides power and data communication path. Can someone confirm my understanding that the Microchip adapter is acting as a Ethernet to USB adapter for communication? I found reference to a LAN7800 USB driver chip while drilling down through one of the documents. I assume that means the end device (i.e. Pi would require the driver support).

 

I'm not familiar with many devices that combine USB port functions of power and communication. The brochure for the product shows a tablet connected as a device. I have an Apple tablet that can act as device but that makes it rather difficult to take measurements under varying loads. In my test scenario I'm thinking I will need a breakout cable to separate Microchip adapter power from the USB signal. As an additional test in my review, I was hoping to use a Android laptop I have as an additional device to test the endpoint. But again I would need to separate power and USB signals.

 

Questions:

What are your expectations at connection point C?

Parents

  • I love this site! I miss the coffee break napkin discussions at work but this site provides the ideal replacement. My thanks to & for making posts to my discussion. Your input enabled me to discover a feature of the the Raspberry Pi. I had never heard of USB OTG (On The Go) or that such a features was available on the Pi.

     

    I followed up on your posts and set out to test the Raspberry Pi USB OTG interface. I assembled a cable that would allow me to connect my laptop USB port to the Pi4B USB-C. I disconnected all peripherals from the Pi4B hoping the laptop USB port could sufficiently power the Pi.  I followed the instructions listed in the links and changed the /boot/config.txt & /boot/cmdline,txt files to enable OTG.

     

    The moment of truth, I plugged the Pi4B into the laptop and booting started. I then attempted to connect to the Pi (previously configured wireless connection) and was rewarded with success. The Pi4B booted! A quick ip a command and I discovered a usb0 interface on the Pi. I then made /etc/dhcpcd.conf configuration to determine if I could assign an IP address to the interface. That was a success also.

     

    I then got lost thinking I could connect to the interface over my network. After some head scratching I realized the errors of my ways. It is not on my network but rather a end to end connection from the laptop to the Pi.  I discovered the laptop had created an addition network interface for the usb port but had no IP configuration. I'm assuming if that interface was configured correctly I would be able to talk. I will leave that for possible RoadTest Review details.

     

    Thanks to your input I have at least one RoadTest Review scenarios to explore. I also think physical separation of data and power on a USB-C is another good investigation scenario.

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  • I love this site! I miss the coffee break napkin discussions at work but this site provides the ideal replacement. My thanks to & for making posts to my discussion. Your input enabled me to discover a feature of the the Raspberry Pi. I had never heard of USB OTG (On The Go) or that such a features was available on the Pi.

     

    I followed up on your posts and set out to test the Raspberry Pi USB OTG interface. I assembled a cable that would allow me to connect my laptop USB port to the Pi4B USB-C. I disconnected all peripherals from the Pi4B hoping the laptop USB port could sufficiently power the Pi.  I followed the instructions listed in the links and changed the /boot/config.txt & /boot/cmdline,txt files to enable OTG.

     

    The moment of truth, I plugged the Pi4B into the laptop and booting started. I then attempted to connect to the Pi (previously configured wireless connection) and was rewarded with success. The Pi4B booted! A quick ip a command and I discovered a usb0 interface on the Pi. I then made /etc/dhcpcd.conf configuration to determine if I could assign an IP address to the interface. That was a success also.

     

    I then got lost thinking I could connect to the interface over my network. After some head scratching I realized the errors of my ways. It is not on my network but rather a end to end connection from the laptop to the Pi.  I discovered the laptop had created an addition network interface for the usb port but had no IP configuration. I'm assuming if that interface was configured correctly I would be able to talk. I will leave that for possible RoadTest Review details.

     

    Thanks to your input I have at least one RoadTest Review scenarios to explore. I also think physical separation of data and power on a USB-C is another good investigation scenario.

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