Rammbock-Erlang is a project mainly written in Erlang, it's free.
Prototyping use of Erlang for asn.1 handling in Rammbock
Erlang prototyping for Rammbock.
To compile tools:
erl
To compile S1AP files:
To decode a binary message:
For more information on Erlang asn.1 handling see http://www.erlang.org/doc/apps/asn1/asn1_ug.html and http://www.erlang.org/documentation/doc-5.2/lib/asn1-1.4/doc/html/asn1ct.html