QMI messages with MC7710

I’m trying to communicate with MC7710 through QMI messages but without success.

First, I use the COM port named ‘AT COMMAND’ to put MC7710 in QMI mode and that works fine.

Then, I had two other ports: NMEA and DM. Which port I should use to send QMI messages?

I’ve made a C# program to comunicate with serial ports. I sent QMI messages (for example QMI_NAS_GET_CELL_LOCATION_INFO) to both ports and MC7710 didn’t respond.

I’ve read QMI documentation from Qualcomm to create correct QMI messages.

What could be wrong?


QMI should sent via the specific qcqmi interface, not the virtual serial ports.

Maybe you can make use of the Windows SDK provided by Sierra Wireless?


lotam, I will use MC7710 inside a specific hardware designed by me and without any kind of Operating System. A CPU will connect directly to MC77010.

The “AirPrime MC7710 Product Technical Specification.pdf” document shows pin assignments. Pins for USB connection are 36 (USB_D-) and 38 (USB_D+). To connect MC770 with my CPU and send QMI messages what are the pins? No other pins allow connection interfaces… :frowning:


Sorry for not clear enough, qcqmi is the name for QMI interface on USB, similar to NMEA/AT port enumerated.

The host controller should detect that endpoint and create the interface and we should send QMI to that particular interface that accept QMI, not the NMEA nor DM port.

You mentioned C# so I guess you are using Windows OS for development? and you probably should also observe the NDIS interface from USB too?

Yes, and to be precise if you really want to develop your own driver: QMI is transported as CDC embedded messages on the network function USB interface(s) of the MC7710, like for example USB interface #8. You really need to dig deep down in the USB communication class spec (yes, the function does pretty much comply with that, despite being labelled as vendor specific) to get started with this.

The physical interface is of course D+, D-. That’s the USB bus connection. But there’s a bit more to USB than just the physical interface…

Anyway, I assume the details above isn’t really what you are looking for at all. The references to “COM port named …” doesn’t really match the “without any kind of Operating System” statement. There is obviously some OS loading a USB host controller driver and a driver for the COM ports (i.e USB serial functions). So, as lotam says:

Yes, use the corresponding NDIS driver for your OS, and whatever API that driver exports for the QMI channel.