Hello,
We are currently trying to setup a ground
station for GMSK modulated AX25 packets at 9600
and 19200.
Our current setup that works is the USRP N200
through GNU radio audio sink and to a Kantronics
9612+ TNC (gmsk_demod.png, quadrature demod ->
audio sink). What we want to do is replace the
hardware TNC with GNU radio packet decoding blocks
and send the packets over TCP.
We first tested the loopback through all the
gmsk mod/demod and packet encoder/decoder blocks,
(gmsk_loopback.png) and this works fine.
However, when we send our received AX.25
packets through GMSK demod -> packet decoder
-> TCP sink (gmsk_demod.png) we do not see
anything on the TCP server side, which tested fine
in loopback.
We are assuming the hangup is in the packet
decoder block as it is not recognizing AX.25
packets or possibly at the end of the GMSK demod
block.
Do we need to look into writing our own packet
decoder block? If we need to do this, is there a
good guide on how to edit existing blocks, or look
at their work() functions?
Do we need to also implement a derandomizer
block before we even can start making sense of the
bit stream?
If we were able to get a byte stream with the
framed AX.25 packets as an output from GNU radio
to our TCP server we can deframe them there
instead of in GNU radio, but we cannot get any
output with this current setup.
Thanks
-Adam
--
Adam K. Gunderson
Space Science and Engineering Lab
Montana State University
address@hidden