EM7455 / MC7455 - Interface USB 2.0 or USB 3.0 ??

IoT Modules MC/EM Series
1

I would like to know if the interface to EM7455 or MC 7455 is a USB 2.0 or USB 3.0 or both are used at the same time independent of each other??

From the datasheet, both are data interfaces, but only the USB 2.0 was stated required. So I am confused, then what does the USB 3.0 interface do??

Or is the 2.0 a fallback of the 3.0, and only either of the interface is required to be connected?

Please advise, thanks!!

2

ut yiu
USB3 SS devices use 3 differential signal pairs: USB2, TX and RX. For backwards compatibility only the USB2 pair is required. You only need the TX and RX pairs if you want to use SS

The MC7455 and EM7455 are like any other USB3 devices.

3

Thanks for the reply.

So that means that if my host processor supports USB 3.0, I only need to connect this USB 3.0 port to the USB 3.0 interface (TX+/-,RX+/-) of the LTE radio module to work; and can leave the USB 2.0 interface of the radio module disconnected.

And if my host processor only has or supports USB 2.0, then I have to of course use the USB 2.0 (D+/-) interface of the LTE radio module; and then leave the USB 3.0 interface of the radio module disconnected.

Please advise if I am right, thanks.

4

You need to connect all USB pairs.

5

No, you don’t. You can connect a USB3 SS device to a USB2 port, or even connect it to a USB3 port using a USB2 cable. This will only connect the USB2 D+ and D-. Works just fine, but is of course limited to USB2 speeds (“high speed” or “full speed”). Nice backwards compatible design.

Similarily, you can get away connecting only D+ and D- of the EM7455 / MC7455 (only considering USB signals - you will need SIM and power too, of course). That’s in fact what Lenovo has done on their laptops, for some reason I have yet to figure out… This limits the USB connection to “high speed”. If you want “super speed”, then you need all 3 pairs.

6

Thats what I meant, connect all USB pairs for USB 3.0. It is not enough to just connect the USB 3.0 pairs and leave the USB 2.0 pair unconnected. Maybe should have written it better.

7

I 've got the same problem. If I connect TX & RX pairs USB3 without USB2 pair, my module doesn’t work.
But if all USB pairs are connected, it works.
I connect my module with USB3 cable on my laptop, how to know if the link USB3 works well ? Because if my USB3 port on my laptop can be out of order, so it can work in Usb2 speed… Are there any command AT to detect a USB2 or USB3 connection ? I don’t find it in the AT command guide.

8

Sure. Of course. Ever wondered why they bothered to put 9 pins in a USB3 connector?

The USB specs are freely available on usb.org/developers/docs/. If you intend to do any hardware design with USB connections, then you should probably skim through a couple of them…

9

Thanks for all the replies everybody.

Overall, to have USB 3.0 capability , both the super speed bus (TX+/-, RX+/-) and the USB2.0 bus (D+/-) need to be connected in order to function. (Cannot just connect the TX+/- , RX+/- signals.)