TUSB4020BI: Interface forum

Thanks Clemens..!

So compared to the image attached, we can add another USB hub to the setup, right?

Regards,

Melbin

Clemens,

For our application, we need to connect at least 120 USB devices in a cascade connection. Could you please suggest any alternate method from what we posted?

Clemens,

Just to clarify our requirement, below is a diagram with six devices connected to USB. Like this, we need to connect a total of 127 devices.

Could you please check whether it is possible?

Thanks,

Melbin

This shows a chain of eight devices (from the host to the rightmost device A), which is not allowed.

Thanks Clemens,

As an alternate, can we connect Ethernet in a cascade connection as above and reach 127 devices?

Thanks

Melbin

Yes, this would be possible. But Ethernet connections are point-to-point; this would require two Ethernet ports on each board.

Using something like RS-485 would allow a common bus. Both ends of the bus need to be terminated. Do you need automatic assignment of device addresses?

Thanks Clemens,

That really helped...!

As an alternate approach for the initial USB interface plan, do you think if it is advisable to replace the USB hub with an MCU?

The proposed connection plan is shown below.  Could you please take a look and let us know up to how many MCUs can be connected as per the new connection plan?

we are aiming for the 1mS scan rate for the peripherals @64 peripherals do you see any concern here

Hi Clemens, could you help us in the above Query! 

In theory, USB has enough bandwidth for 64k samples per second. In practice, this depends on what protcol you use and how the MCU firmware is implemented, and I guess there will be a latency of at least one USB frame for each step in the chain.