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sekigon-gonnoc / Pico-PIO-USB

USB host/device implementation using PIO of raspberry pi pico (RP2040).
MIT License
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Resistors For USB Host #101

Open Norto04 opened 1 year ago

Norto04 commented 1 year ago

Does this project follow the USB Specification for the host implementation? Im having trouble understanding if it requires 15k (changed to 14.5k - 24.8k) resistors and if there something that needs to be disconnected after the device negotiates what speed its using. Or does PIO USB implement this somewhere I havent seen? There is a resistor pdf in the link below.

https://www.usb.org/sites/default/files/usb_20_20230224.zip

P.S, What are the 22ohm resistors mentioned in the README used for?

drojf commented 9 months ago

I was wondering too. I don't have a proper answer, but I saw this application note describing these 22 ohm resistors and thought it might be useful: https://www.onsemi.com/pub/collateral/and8074-d.pdf

I think the 15K pull up and 1.5K pull down are for indicating upstream/downstream and low speed/full speed.

I'm not sure how these can be omitted (See Adafruit's RP2040 USB Host Schematic with only 22ohm resistors) but I guess it works anyway.