Merlin U720 USB and Linux?

futrader · EVDO Newbie Joined: 12 Dec 2006 Posts: 7

Actually, recent kernels DO know how to properly handle these devices. However, the generic usbserial module does not. They require special handling. So the kernel needs to be patched to identify the devices and give them the special handling they need. You need to make sure the linux kernel file airprime.c contains identifiers for the devices. The plus signs indicate additions for new devices:

--- airprime.c 2006-12-28 17:23:57.000000000 -0600
+++ /usr/src/linux/drivers/usb/serial/airprime.c 2007-01-02 18:36:29.000000000 -0600
@@ -19,7 +19,11 @@
static struct usb_device_id id_table [] = {
{ USB_DEVICE(0x0c88, 0x17da) }, /* Kyocera Wireless KPC650/Passport */
{ USB_DEVICE(0x1410, 0x1110) }, /* Novatel Wireless Merlin CDMA */
+ { USB_DEVICE(0x1410, 0x1130) }, /* Novatel Wireless S720 CDMA/EV-DO */
+ { USB_DEVICE(0x1410, 0x2110) }, /* Novatel Wireless U720 CDMA/EV-DO */
+ { USB_DEVICE(0x1410, 0x1430) }, /* Novatel Merlin XU870 HSDPA/3G */
{ USB_DEVICE(0x1410, 0x1100) }, /* ExpressCard34 Qualcomm 3G CDMA */
+ { USB_DEVICE(0x413c, 0x8115) }, /* Dell Wireless HSDPA 5500 */
{ },
};
MODULE_DEVICE_TABLE(usb, id_table);

The instructions given previously, to modprobe usbserial with the vendor id and the product id is wrong. It will result in the device being handled by the generic usbserial driver, not the special handling of the airprime subdriver. You need to actually patch the kernel to get the desired result.

After making this patch, my speed results using the slightly older 2.6.19 kernel match the previous results for the 2.6.20-rc2 kernel.

futrader · EVDO Newbie Joined: 12 Dec 2006 Posts: 7

If your kernel is of recent enough vintage that it includes the patches to airprime.c that fix the handling of high speed usb serial transfers, but still old enough that this device is not automatically associated with airprime, it might suffice if after doing "modprobe usbserial vendor=0x1410 product=0x2110" you then also do "modprobe airprime".

If you are getting bad speeds using the procedures recommended on the first page of this thread, try the "modprobe airtime" and see if it fixes the problem.

futrader · EVDO Newbie Joined: 12 Dec 2006 Posts: 7

One thing I've noticed under Linux is that if the connection downgrades from EVDO Rev A to 1xRTT (eg if traveling away from an EVDO coverage or if in a marginal area with fluctuating signal strength) the U720 does not seem to upgrade itself back to EVDO when the coverage is available again.

It appears that with Windows the connection will migrate from EVDO to 1xRTT and back as the coverage is available.

I wonder if anyone else has had this experience. It appears to me that the Windows connection manager software must detect the coverage availability, and if an upgrade from 1xRTT to EVDO is possible, it must somehow nudge the device to somehow do the upgraded connection.

If I unplug the U720 for a few seconds and then plug it back in, it will then reaquire EVDO if available. But manual intervention seems to be required.