Cycle-time-measurement-POWERLINK-on-raspberry-pi-2

 

To measure performance of the pcap POWERLINK demo while

• IO data is exchanged in the isochronous phase and
• A video is streamed over the asynchronous phase

     

Figure – 1 Environment Set up

   

Configuration

• Cycle Time: 50 ms
• Isochronous Data Size: 1 Byte Tx & 1 Byte Rx
• Asynchronous Data Size: 1500 Bytes
• The demo C program on the slave receives the data and loops it back into the network

 

Performance

• The master is able to receive the data is sent into the network after the loop back at a delay of 200ms i.e. 4 cycles.

 

Figure – 2 Round trip time of a PDO

 

• During the process master streams a video with the resolution of 176×144 @ 25fps into the network. One of the slaves in the network receives the streamed video with the delay of 2 seconds. The persistence (jitter) between the cycles was measured to be 4ms during the process.

 

Figure – 3 Jitter measurements

   

• We see that the network is stable and deterministic at 50 ms
• To further reduce the cycle time, we can port the ethernet driver into the Linux kernel and try using RtPreempt