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PC support for low speed USB (1.5Mbps)

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Eugen_E

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According to the USB standard, a full speed USB host (12Mbps) should support full speed (12Mbps) and low speed (1.5Mbps) devices. A high speed USB host (480Mbps) should support high speed and full speed, but not necessary low speed.

I want to ask what is your experience in connecting low speed devices to modern PCs with high speed USB.
I want to design a low speed USB device based on AVR uC (app note AVR309, and other sources) and want to know if I will have problems in connecting it to some PCs. If there isn't support for low speed anymore I will use FT232 for USB/RS232 conversion.

Thanks.
 

I tried this **broken link removed** it's a RS-232 to USB converter with ATmega8, this is low speed usb app and it works perfect with my PC (asus P4 motherboard, usb 2.0) also it works with usb 2.0 hubs and usb 2.0 PCI cards, so i think there is support for low speed devices in usb 2.0
 

    Eugen_E

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From Chapter 7 of USB Specification

A USB 2.0 downstream facing transceiver must support high-speed, full-speed, and low-speed modes.
 

    Eugen_E

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Hi,

If you one the device details in modern PCs you will find two major host controller.
UHCI - Supported for Full/low speed
EHCI - for High speed alone
Depend on the speed settling the data will be routed to the host.

Thanks
 

Thanks for the replies. I will use low speed USB on AVR according to AVR309 appnote.
 

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