RS232 performance improvement

Technical Support
1

Dear, we are implementing a product that makes extensive use of RS232 sensors. Any suggestion on how to make the RS232 link more “real time”?

System details:
Apalis iMX8
Ixora Carrier Board
OS:
TorizonCore 6.5.0
or
TorizonCore 5.7.2

2

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Hello,

Improving the “real-time” performance of RS232 links in your system involves optimizing both hardware and software components. Here are some suggestions tailored for your Apalis iMX8 on the Ixora Carrier Board running TorizonCore:

Hardware Considerations

  1. Cable Quality and Length: Ensure you’re using high-quality RS232 cables. Shorter cables can reduce signal degradation and improve communication reliability.
  2. Shielding and Grounding: Proper shielding and grounding can minimize noise that might interfere with the RS232 signals, improving the reliability of the communication.

Software Optimizations

  1. Real-Time Kernel: Consider using a real-time Linux kernel. While TorizonCore is optimized for performance, a real-time patch can further reduce latencies. Check if there’s a real-time variant of TorizonCore available for your version, or consider customizing the kernel with real-time patches.
  2. Priority Scheduling: Use real-time scheduling policies for your processes or threads that handle RS232 communication. The SCHED_FIFO or SCHED_RR policies can be applied to prioritize your RS232 handling tasks over less critical processes.
  3. Buffer Sizes and Serial Settings: Adjust the buffer sizes and serial port settings (baud rate, parity, stop bits) to match the requirements of your sensors and application. This can help in reducing delays in data processing.
  4. Disable Unnecessary Services: Minimize the background processes and services running on your system. This can free up CPU cycles and reduce the system’s overall load, improving the responsiveness of your RS232 communication tasks.
  5. Direct Memory Access (DMA): If your RS232 communication is handled by a peripheral that supports DMA, ensure it’s enabled. DMA can offload the CPU by directly moving data between the peripheral and memory, reducing latencies and improving throughput.

Monitoring and Debugging

  • Real-Time Performance Monitoring: Tools like htop, iostat, and vmstat can help monitor system performance and identify bottlenecks. For real-time specific monitoring, consider using rt-tests (like cyclictest) to measure system latencies.
  • Serial Port Debugging Tools: Use tools like minicom or screen to interact with your RS232 devices. These tools can also help in debugging communication issues.

Development Practices

  • Incremental Testing: When implementing changes, test incrementally to identify which modifications have the most significant impact on performance.
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Please, also check if these links can help you solve your problem:

U-Boot | Toradex Developer Center.

3

Hello @rmarra,

May I ask what you mean by more realtime?
What are your timing constraints?
What kind of sensor are you using and the sampling rate at which the sensor is sampled?
Which UART speed settings are you using?

Best Regards,
Matthias