.. _cspifc:

==============
CSP Interfaces
==============

The SRS-3 transceiver is operated remotely via `CubeSat Space Protocol (CSP) <http://www.libcsp.org/>`_ messages. The :ref:`srs3-client` and :ref:`prop-client` all contain wrapper function around CSP protocols. In addition, SRS-3 also implements the standard CSP service ports such as ``CSP_PING`` and ``CSP_REBOOT``.

Configuration CSP parameters
----------------------------

By default, the system uses address 21 but this can be changed by adjusting the address property ``sys.csp.address`` and saving the ``sys`` group. The system must be rebooted for the address change to take effect.

The system supports CSP via CAN-bus (``CAN`` interface) and RS-422 (``KISS`` interface) in the P1 connector, and through the spacelink (``SPACE`` interface). The interfaces are always enabled for incoming messages, but the default routing table sends egress messages on the CAN interface for all traffic except traffic to ground (address 10) and loopback.

Note that the CAN interface by default operates in CSP/CFP "promiscuous" mode, meaning that the SRS-3 will receive, and potentially forward, all CSP frames on the CAN-bus regardless of the CSP/CFP destination address. This behaviour can be disabled by setting the ``sys.can.promisc`` property to false.

The current routing table can be listed using the ``csp route show`` command in the debug shell:

.. code-block:: none

    [srs-3] csp route show 
    21/5 LOOP
    0/0 CAN
    10/5 SPACE

The results are listed using `CIDR notation <https://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing>`_. CSP addresses are 5 bits long so, ``21/5`` is an exact match to address ``21``, i.e. the loopback address. ``0/0`` marks the default route. To adjust CSP routing, the ``sys.csp.routes`` property should be used. As an example, to send all traffic via the RS-422/KISS interface set the property to ``0/0 KISS`` and save the ``sys`` group. It is not necessary to add an explicit route for the loopback interface.

The CSP connection can be tested using the ``csp ping`` debug shell command. This can be combined with the ``watch`` command to e.g. ping a system 10 times and report the number of successful replies. This example pings address 1 with 100 byte frames:

.. code-block:: none

    [srs-3] watch -c10 -s csp ping -s100 1
    Running command 'csp ping -s100 1' every 1000 ms
    Reply in 4 ms
    Reply in 4 ms
    Reply in 4 ms
    Reply in 4 ms
    Reply in 5 ms
    Reply in 5 ms
    Reply in 4 ms
    Reply in 4 ms
    Reply in 4 ms
    Reply in 6 ms
    10 executions, 10 success 0 failures
