Update IV
Patched kernel-ppp.c to show what is wrong with the incoming
packages. Well, almost all packages come with bad FCS (Frame
Check Sequence), that means the data packet got corrupted
somweher in the serial chain. And I mean almost _all_ (> 90%) of
them are bad.
Change the baudrate from 115200 to 57600, no effect. Replaced
the kernel-serial.c with a version from a sl-5500 kernel, no
effect.
I even slipped the modem-card back into the sl5500 (worked
instantly) and hold the antenna close to the C3000 (I thought
there might be some interference from the C3000) but the
connection continued to work well in the sl5500.
Conclusion: I have not the slidest idea what the hell is going
on. I know, the scripts are ok, the modem is ok, the provider
works well (all tested with the SL5500), I replaced serial_cs.c
with different versions from different Zaurus and Vanilla kernels,
I replaced serial.c with other Zaurus und vanilla versions, all
to no avail. I tried a different pppd - all gives me the same
result. The only difference is the interrupt, the modem card
is assigned to : On the SL5500 it's IRQ35, on the C3000 its
IRQ 135 (even though that does not seem to be a problem,
see Update III).
I need that modem running. After all, what is a pda good for
if you can't take it outside and still keep connected .. ?