AnyDATA ADU-500A CDMA Rev. A USB-modem works via ubsa.ko
This device need to catch NO CARRIER to disconnect correctly. WinXP does it with lowering DTR to 0.

In ppp.conf is following
evdo:
 set device /dev/cuaU0
 set speed 115200
 set mru 1400
 set mtu 1400
 set timeout 160
 disable mppe
 set phone \#777
 set dial "ABORT BUSY ABORT ERROR ABORT NO\\sCARRIER TIMEOUT 5 \"\" ATZ OK AT OK "ATE0V1&F&D2&C1S0=0" OK ATX1 OK AT OK \\dATDT\\T TIMEOUT 40 CONNECT"
 set logout "ABORT BUSY ABORT ERROR ABORT NO\\sCARRIER TIMEOUT 30 \"\" ATH\\sE1 OK"
 set authname bwc
 set authkey bwcbwc
 set login
 set ifaddr 10.0.0.1/0 10.0.0.2/0 255.255.255.0 0.0.0.0
 add default HISADDR

All AT-commands got from windows driver.
It is working good, but when I disconnect with killing ppp it doesn't disconnect and write this to log.
May 25 01:10:00 irk-gw ppp[1468]: tun0: Warning: deflink: Unable to set physical to speed 0
May 25 01:10:00 irk-gw kernel: ucom0: ubsa_request(0, 18): STALLED
May 25 01:10:00 irk-gw kernel: ucom0: ubsa_request(3, 0): STALLED
May 25 01:10:00 irk-gw kernel: ucom0: ubsa_request(2, 3): STALLED
May 25 01:10:00 irk-gw kernel: ucom0: ubsa_request(1, 0): STALLED
May 25 01:10:00 irk-gw kernel: ucom0: ubsa_request(10, 180): STALLED
May 25 01:10:00 irk-gw kernel: ucom0: ubsa_request(a, 0): STALLED
Modem still online after disconnect and to connect again I need to swith off usb-cable and than switch it on.

How-To-Repeat: ppp -ddial evdo
killall ppp.
cu -l /dev/cuaU0
you'll see that modem is sending data and doesn't disconnect.
Again ppp -ddial evdo will not connect.