= Troubleshooting =

Known problems with the LMT connection

Problem:
'bs11_config' can't get a connection to the BS-11 (no 'LMT LOGON: ACK')

Solution:
The BS-11 is a little bit choosy about the RS232 levels, I discovered some problems
with my Dell PC (could receive anything, but no tx). Just switch to an el-cheapo USB
to Serial adapter, this should solve the problem.

Some background notes:
We measured the RS232 levels and we found out that the level of our RS232<==>USB Adaptor
is much lower (about /-6 Volts) than normaly expected (/-12V). The BS11 transmits at a
semeliar level (about /-8 Volts). This may be an explaination why the BS11 does not like
the normal (/-12V) levels.

Image(Lmt_bts-rx.jpg, 15%) Image(Lmt_bts-tx.jpg, 15%) Image(Lmt_btx_tx_does_not_work.jpg, 15%)

From left to right: BTS-RX (PC-TX), BTS-TX (PC-RX), BTS-RX (PC-TX) with a real RS232 port.

The "everything looks good - nothing works" - problem

When you use openBSC with early mISDN drivers (<= 2.6.31, patched) your setup might refuse
to work while everything looks normal. No error messages, normal PLL Work Value Abis Link
works perfect but no phone can see your network.

Than the first thing you should do is to upgrade your kernel to get the latest mISDN drivers.

Note: When your BS11 is out of Sync the setup also refuses to work. In this case you
sould sync your BS11 as described in the isdnsync-howto.

See also:
http://lists.gnumonks.org/pipermail/openbsc/2009-August/000783.html