Random communication_constraint_violation with libfranka 0.9.2 due to jitter in update()

[mikelasa]

Hello,

I’ve been working with a Franka Emika Panda robot using libfranka 0.9.2. For my project, I implemented my own franka class with functionalities of robot_impl.h in order to run a custom control loop.

• When running the standard libfranka examples, I never experienced communication issues.
  

• After finishing my custom control implementation (which works as expected otherwise), I’m now facing random packet losses with the error: communication_constraint_violation.
  

• Debugging showed that the problem comes from random large jitter during the call to the update() function (robot_impl.h). Occasionally, I see spikes up to 3 ms, even though my control code itself always runs well below 1 ms always.
  

My setup:

• Ubuntu 22.04
  

• Realtek RTL8126 NIC (onboard)
  

I’ve read in the Franka documentation and in other forums that it’s strongly recommended to use a dedicated NIC, e.g. the Intel i350.

My question: Since I’ve confirmed that the jitter is happening inside update() and not in my control code, should I assume that the Realtek NIC is the bottleneck and invest in a dedicated Intel card? Has anyone experienced similar random jitter with Realtek adapters?

Thanks in advance for any advice or experiences.