Hi David,
Most of the things you have tried I haven't so I would not be able to help you with those, but I do have pppd with the chat script working so I may be able to help with that.
On my distro pppd and chat both log what they are doing to syslog, so if ypu could find the relavent lines in syslog and post them here I, and maybe others too can have a look so see what is going wrong.
On my system these are found in /var/log/syslog though the exact location may be distro dependant. You are looking for lines like:
Nov 10 22:45:43 localhost pppd[6397]: pppd 2.3.11 started by <...>, uid 1234 Nov 10 22:45:45 localhost chat[6398]: abort on (BUSY) Nov 10 22:45:45 localhost chat[6398]: abort on (NO CARRIER) Nov 10 22:45:45 localhost chat[6398]: abort on (VOICE) Nov 10 22:45:45 localhost chat[6398]: abort on (NO DIALTONE) Nov 10 22:45:45 localhost chat[6398]: abort on (NO DIAL TONE) Nov 10 22:45:45 localhost chat[6398]: abort on (NO ANSWER) Nov 10 22:45:45 localhost chat[6398]: send (ATZ^M) Nov 10 22:45:45 localhost chat[6398]: expect (OK) Nov 10 22:45:45 localhost chat[6398]: ATZ^M^M Nov 10 22:45:45 localhost chat[6398]: OK Nov 10 22:45:45 localhost chat[6398]: -- got it Nov 10 22:45:45 localhost chat[6398]: send (ATM0^M) Nov 10 22:45:45 localhost chat[6398]: expect (OK) Nov 10 22:45:45 localhost chat[6398]: ^M Nov 10 22:45:45 localhost chat[6398]: ATM0^M^M Nov 10 22:45:45 localhost chat[6398]: OK Nov 10 22:45:45 localhost chat[6398]: -- got it Nov 10 22:45:45 localhost chat[6398]: send (ATDT0123456789^M) Nov 10 22:45:45 localhost chat[6398]: expect (CONNECT) Nov 10 22:45:45 localhost chat[6398]: ^M Nov 10 22:46:08 localhost chat[6398]: ATDT0123456789^M^M Nov 10 22:46:08 localhost chat[6398]: CONNECT Nov 10 22:46:08 localhost chat[6398]: -- got it Nov 10 22:46:08 localhost chat[6398]: send (\d) Nov 10 22:46:09 localhost pppd[6397]: Serial connection established. Nov 10 22:46:09 localhost pppd[6397]: Using interface ppp0 Nov 10 22:46:09 localhost pppd[6397]: Connect: ppp0 <--> /dev/ttyS0 Nov 10 22:46:10 localhost pppd[6397]: sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0xab37101b> <pcomp> <accomp>] Nov 10 22:46:13 localhost pppd[6397]: sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0xab37101b> <pcomp> <accomp>] Nov 10 22:46:14 localhost pppd[6397]: rcvd [LCP ConfReq id=0x1 < 00 04 00 00> <mru 1524> <asyncmap 0x0> <auth pap> <pcomp> <accomp> < 11 04 05 f4> < 13 09 03 00 c0 7b 70 fa ad>] Nov 10 22:46:14 localhost pppd[6397]: sent [LCP ConfRej id=0x1 < 00 04 00 00> < 11 04 05 f4> < 13 09 03 00 c0 7b 70 fa ad>] Nov 10 22:46:14 localhost pppd[6397]: rcvd [LCP ConfAck id=0x1 <asyncmap 0x0> <magic 0xab37101b> <pcomp> <accomp>] Nov 10 22:46:14 localhost pppd[6397]: rcvd [LCP ConfReq id=0x2 <mru 1524> <asyncmap 0x0> <auth pap> <pcomp> <accomp>] Nov 10 22:46:14 localhost pppd[6397]: sent [LCP ConfAck id=0x2 <mru 1524> <asyncmap 0x0> <auth pap> <pcomp> <accomp>] Nov 10 22:46:14 localhost pppd[6397]: sent [LCP EchoReq id=0x0 magic=0xab37101b]Nov 10 22:46:14 localhost pppd[6397]: sent [PAP AuthReq id=0x1 user="kkiijj" password=<hidden>] Nov 10 22:46:14 localhost pppd[6397]: rcvd [LCP EchoRep id=0x0 magic=0x0] Nov 10 22:46:14 localhost pppd[6397]: rcvd [PAP AuthAck id=0x1 ...] Nov 10 22:46:14 localhost pppd[6397]: local IP address 1.2.3.4 Nov 10 22:46:14 localhost pppd[6397]: remote IP address 5.6.7.8