Your Linux Data Center Experts

IBM Candlestick CDPD under Linux

By  Sean Reifschneider Date November 25, 2004

This modem works great under Linux, as long as you patch the PCMCIA code (see below) and are in a CDPD coverage area. Luckily, Colorado has great coverage. Hopefully, with AT&T; really pushing the "PocketNet" phones (which use CDPD), the coverage area will expand. Note that AT&T; no longer supports using these modems with their service.

Just as a background, the modem talks SLIP to the computer, and mediates sending packets to the cellular network. When you do an "ATD", you should immediately get a "CONNECT" (you are connecting to the modem itself, remember), and then within a few seconds you'll start getting SLIP data. It'll take 30 seconds or so before the little tower light comes on, and about another 15 seconds before the network will start responding.


These modems take a fairly long time to start up. The standard PCMCIA code will check too early and think that the card is a memory card. Add the following patch (or just change cs.c so that "unreset_limit" is 100):

--- linux-2.4.0-test2/drivers/pcmcia/cs.c.old	Sat Jul  1 10:06:05 2000
+++ linux-2.4.0-test2/drivers/pcmcia/cs.c	Sat Jul  1 10:06:23 2000
@@ -110,7 +110,7 @@
 INT_MODULE_PARM(reset_time,	10);		/* usecs */
 INT_MODULE_PARM(unreset_delay,	HZ/10);		/* ticks */
 INT_MODULE_PARM(unreset_check,	HZ/10);		/* ticks */
-INT_MODULE_PARM(unreset_limit,	30);		/* unreset_check's */
+INT_MODULE_PARM(unreset_limit,	100);		/* unreset_check's */
 /* Access speed for attribute memory windows */
 INT_MODULE_PARM(cis_speed,	300);		/* ns */

Configuration Commands

AT&F;Reset the modem to factory defaults.
AT+WVNEI=1,"0000"Select the CDPD NEI for programming.
AT+WVIPADD="123.456.789.123","0000"Input the IP address (Obtained from service provider)
AT+WS46=4Set modem to CDPD SLIP mode (the only one supported by AT&T;).
AT&W;Write the configuration to the modem.
ATZSoft reset the modem.
ATDMake a test call, you should get "CONNECT" immediately, then within 30 seconds get some SLIP garbage.

DIP Script

I also have a sample DIP script to get this modem working under Linux.


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