CSP Interfaces

The SRX-8 transmitter is operated remotely via CubeSat Space Protocol (CSP) messages. The SRX-8 Client Library and Property Client Library all contain wrapper function around CSP protocols. In addition, SRX-8 also implements the standard CSP service ports such as CSP_PING and CSP_REBOOT.

Configuration CSP parameters

By default, the system uses address 28 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. The interfaces are always enabled for incoming messages, but the default routing table sends egress messages on the CAN interface for all traffic except loopback.

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

[srx-8] csp route show
28/5 LOOP
0/0 CAN

The results are listed using CIDR notation. CSP addresses are 5 bits long so, 28/5 is an exact match to address 28, 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 stack is configured for 256 packet buffers of up to 1024 bytes. The CAN and KISS interfaces both have an MTU of 1024 bytes.

The CSP connection can be tested using the csp ping EGSE shell command. The example below pings satctl on address 2 with 100 byte frames 10 times:

[srx-8] csp ping -s100 -c10 -r 2
Reply in 3.000 ms
Reply in 3.000 ms
Reply in 3.000 ms
Reply in 3.000 ms
Reply in 3.000 ms
Reply in 3.000 ms
Reply in 3.000 ms
Reply in 3.000 ms
Reply in 3.000 ms
Reply in 3.000 ms
Sent: 10 Received: 10 (100.0%) Lost: 0 (0.0%)
RTT: min=3.000 max=3.000 avg=3.000