• 21
      Jul - 2018

      Real Time Systems | 6 min | 4758

      #Raspberry Pi: Real Time System - Xenomai Patching Tutorial for Kernel 4.14.y

      Real Time Systems | 6 min | 4758


      kernel patching
      raspberry pi
      real time system
      xenomai

      The website of Xenomai says the following about it Xenomai:

      Xenomai brings POSIX and traditional RTOS APIs for porting time-critical applications to Linux-based platforms. When the native Linux kernel cannot meet the response time requirements of the application, Xenomai supplements it with Cobalt, a small real-time infrastructure which schedules time-critical activities independently from the main kernel logic.

      Checking the list of supported hardware, the Raspberry Pi 2, 3 B(+) ARM micro (BCM2835) is included.

      This tutorial is almost the same as the tutorial for Preempt-RT patching, but in ...

    • 21
      Jul - 2018

      Real Time Systems | 8 min | 8432

      #Raspberry Pi: Real Time System - Preempt-RT Patching Tutorial for Kernel 4.14.y

      Real Time Systems | 8 min | 8432


      kernel patching
      preempt-rt
      raspberry pi
      real time system

      The Preempt-RT tutorial article is the most visited post on my blog. Therefore, I decided to update the tutorial to make it cleaner, and to introduce some other possible modifications and tips for solving problems.

      Preempt-RT is a popular patch for the Linux kernel to transform Linux into such a real-time operating system. There is another option to get this done, and that's Xenomai (tutorial and performance tests here).

      Tiejun Chen, the main responsible for the official Raspberry-Pi-RT branch, has published a video about Preempt-RT here. It includes tips, results and tests.

      Getting the Sour...

    • 01
      Apr - 2018

      Real Time Systems | 5 min | 1141

      #Raspberry Pi: The N-queens Problem (benchmark) Preempt-RT vs. Standard Kernel

      Real Time Systems | 5 min | 1141


      n-queen problem
      performance
      preempt-rt
      raspberry pi
      standard kernel

      N-Queens Problem: A Benchmarking Solver for Raspberry Pi

      The N-Queens Problem/Puzzle is a well-known problem that consists of placing N chess queens on an N × N chessboard so that no two queens attack each other. For example, one possible solution to the N-queens problem for N = 4 is the following:

      N-queens problem (N=4)
      Fig. 1: N-queens problem example (N = 4). Source: Google Optimization Tools

      As you can see, no two queens are on the same row, column or diagonal. Usually the problem consists to find all possible solutions, rather than one optimal solution.

      I wrote a script in Python that calculates ...

    • 01
      Apr - 2018

      Real Time Systems | 3 min | 2341

      #Rapberry Pi: Preempt-RT Kernel Performance on Rasbperry PI 3 Model B+

      Real Time Systems | 3 min | 2341


      kernel
      patching
      preempt-rt
      raspberry pi 3 B plus
      standard

      The Raspberry Pi 3 Model B+ (Fig. 1) is now on sale and I bought one two weeks ago. The main modifications are the followings:

      • A 1.4GHz 64-bit quad-core ARM Cortex-A53 CPU
      • Dual-band 802.11ac wireless LAN and Bluetooth 4.2
      • Faster Ethernet (Gigabit Ethernet over USB 2.0)
      • Power-over-Ethernet support (with separate PoE HAT)
      • Improved PXE network and USB mass-storage booting
      • Improved thermal management
      Raspberry Pi 3 B+
      Fig. 1: Raspberry Pi 3 Model B+

      The Raspberry Pi uses now the LAN2515 chip from Microchip instead of the LAN9514 for Ethernet and the USB Ports.

      If you are looking for some Benchmarkin...

    • 19
      Mar - 2018

      Real Time Systems | 1 min | 442

      #Raspberry Pi: Preempt-RT Kernel 4.14.y on Raspberry Pi

      Real Time Systems | 1 min | 442


      kernel patching
      official branch
      preempt-rt
      raspberry pi

      The forked rpi-4.14.y-rt repo by TiejunChina is now a branch under the official Raspberry Pi repo. That means you need to type the following to clone the Preempt-RT patched Kernel

      ~/rpi-kernel$ git clone https://github.com/raspberrypi/linux.git
      ~/rpi-kernel$ cd linux
      ~/rpi-kernel/linux/ git checkout rpi-4.14.y-rt

      Then, you can follow the tutorial from here.

    • 12
      Mar - 2018

      Real Time Systems | 2 min | 1185

      #Raspberry PI Zero W: Preempt-RT Kernel Performance

      Real Time Systems | 2 min | 1185


      kernel
      patching
      performance
      preempt-rt
      raspberry pi zero
      standard

      Today I patched the kernel of a Raspberry Pi Zero W with Preempt-RT. I used the repo TiejunChina.

      Update 18.03.2018: The official Preempt-RT patched Rasbian repo is here.

      ##~/rpi-kernel$ git clone https://github.com/TiejunChina/linux.git # update 18.03.2018: old repository##
      
      ~/rpi-kernel$ git clone https://github.com/raspberrypi/linux.git # update 18.03.2018: new repository
      ~/rpi-kernel$ cd linux
      ~/rpi-kernel/linux$ git checkout rpi-4.14.y-rt  # today the kernel version is 4.14.22
                                                      # with rt17 resulting in 4.14.22-rt17+ 

      You can find a complete...

    • 26
      Feb - 2018

      Real Time Systems | 5 min | 3246

      #Raspberry Pi: Preempt-RT vs. Standard Kernel 4.14.y

      Real Time Systems | 5 min | 3246


      kernel patching
      latency
      performance
      preempt-rt kernel
      raspberry pi
      standard kernel

      The last week I was working on a real-time application (with a 1 ms sample time) that runs on an ARMv8 Cortex-A53 (Raspberry Pi 3 Model B based board) and I was wondering the differences between latencies on the standard and the Real-Time (RT) Linux kernel. I had some problems with the standard kernel version, then I thought I could analyze the latencies of both kernels, and make some conclusions. Many test are available but with older kernel versions. The tests were performed using the Raspbian Kernel 4.14.21 and the Preempt-RT Patch 4.14.21-rt17!

      Hardware & Software

      To follow the DIY parts, ...

    • 26
      Feb - 2018

      Real Time Systems | 7 min | 10873

      #Raspberry Pi: Preempt-RT Patching Tutorial for Kernel 4.14.y

      Real Time Systems | 7 min | 10873


      kernel patching
      preempt-rt
      raspberry pi
      raspbian
      standard kernel

      There are a lot of tutorials for Raspberry Pi kernel patching using Preempt-RT, but I needed about 15 hours to get it working! I hate Kernel patching! and I have to say, that's not my first time. I have a system working with Ubuntu, RTAI and an Ethercat master. I patched the system more than once. But it is/was always a new thing! and It costs a lot of time! ;)

      Then, you have another tutorial here. I only hope that the repo gets official. It could reduce the time to get the RT ...