Juggling two USB devices with one USB host (MAX3421E)

[eecsninja]

Hi everyone, new member here.

I designed a circuit that has a USB port connected to a MAX3421E host, which has only one port. I'm wondering if I can multiplex two or more USB devices on one such host by tri-stating their power and ground rails using a microcontroller's GPIOs. I.e. only one USB device will have power and ground connected at a time.

 

[IanP]

Hi everyone, new member here.

I designed a circuit that has a USB port connected to a MAX3421E host, which has only one port. I'm wondering if I can multiplex two or more USB devices on one such host by tri-stating their power and ground rails using a microcontroller's GPIOs. I.e. only one USB device will have power and ground connected at a time.

Physically you can connect extra devices via tri-state power switches, but the problem will arise with the enumeration of a device after the power is applied to it.
Is the host “smart” enough to detect and enumerate your added devices (one at a time)?
:wink:
IanP

 

[oyvdahl]

I think there might be some problems with this. I believe the USB host will query USB devices from time to time to check if they are working properly (I haven't double checked this)

I would suggest using a USB hub chip like this one https://www.ti.com/product/tusb2036
I used it a couple of years ago in a project and it was really simple to get working.

Cheers!
Oyvind