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.
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.
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.