MC7700 SYNC Errors


I’m having a problem with my MC7700 under Linux. I have it hooked up to a dev kit, which is connected via USB to a Linux machine running the latest stable Ubuntu build. The card connects and starts working, I can see is with lsusb, and I can talk to it with cutecom. I sent it some AT commands and it responded correctly.

After maybe 30-45 seconds, it stops responding to my input. All input stops working and it won’t echo anything I send it (in one case it was in the middle of echoing my last command when it stopped). I used dmesg and it shows tons of these:

wwan0: Submit SYNC failed -32
wwan0: Send SYNC failed, status -32

These are printed over and over every few seconds. I’m confused – I haven’t ordered it to do anything. What’s failing? What I observed was identical to this:

I don’t know what to do differently; all I did was look at the APNs and do ATI and ATE1. It still stops communicating if I don’t do anything at all. Is there some driver or firmware I need to install? It seems to be recognized fine, but it quits working quickly. Any help would be appreciated, thanks.


I believe this is the problem Dan describes (and tries to fix) here:

The fix is not yet finished cooking, I believe. But if this is the problem, then I guess you can work around it by forcing the network interface up before the firmware crashes. I.e. do something like

ip link set wwan0 up

before anything else.