I am really happy to inform you that I will be at the Hannover Fair 2018. The Institute of Mechatronic Systems will be represented by our research group "Integrated Systems and Machine Learning" in the Hall 2 on Stand B08 and we will be presenting solutions for the advancing digitization of industrial production.

The Hannover Fair 2018 takes place between Apr 23, 2018 and Apr 27, 2018 in Hannover.

For more info, click here:

You find the map below:

I am writing this post as a tutorial or a 'keep' note for myself, but I think it could be interesting for a lot of people. At work I'm using a Latitude Dell Laptop with dual boot (Ubuntu 16.04 LTS and Windows 10). The laptop has a SD card reader. Usually I work under Ubuntu while I am programming, and the SD card reader support is broken! But typing the following on a terminal, makes it works again:

sudo rmmod sdhci_pci sdhci_acpi sdhci
sudo modprobe sdhci debug_quirks2="0x10000"
sudo modprobe sdhci_pci sdhci_acpi sdhci

It seems to be a problem since Linux kernel version 4.1.8. A bug report here confirms it, with the possible workaround here.

To make this workaround permanent, you need to create a .conf file with the debug_quirks option in the folder /etc/modprobe.d/. Executing the following command on a terminal creates the needed file:

sudo sh -c 'echo options sdhci debug_quirks=0x10000 >> /etc/modprobe.d/sdhci-pci.conf'

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:

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 the number of all possible solutions. This script can be used as Benchmark for e.g. the Raspberry Pi.

Many people use the N-queens problem to test the performance of a defined solver. But this can be cheated. In my case, the solver (script) is not optimal (I implemented the backtracking way based on this solution), but it works, and it helps me to compare different configurations of the Raspberry Pi (kernel, model B & B+ etc.). I solved the N-queens problem for N=12, in single (ST) and multi-thread (MT) configurations and repeated the tests 45(ST)/100(MT) to check the result variances.

All the data, scripts and notebooks are available here:

	Code: https://github.com/lemariva/rPI-Tests

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

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 Benchmarking of the new model, Gareth Halfacree has some nice graphics on his website.

If you are planning to use a heatsink on the new model, please check that the new SoC packaging has a hole, and you shouldn't cover it. Some people are writing that the heat spreader (metal bit on the Fig. 1) reaches to dissipate the heat generated and you don't need an extra heatsink. But, if you are like me, and you are using the Raspberry Pi for (near) real-time applications, with data processing, you should use some additional cooling system. It goes really hot!. The PXE Ethernet Hat, which is coming soon, has a fan. It could be an option!

As usual on my last posts, I compiled the last version of the Preempt-RT Patched Kernel to test its performance on this new model.

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.

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 tutorial for patching a Raspbian kernel 4.14.y here.

Check the options for Raspberry Model A(+), B(+), Zero W.

(perfomance tests and problems inside!)

I've been working with web development this weekend. I hope you didn't have to wait because of a maintenance dialog or a 500 error due to the updates! I updated three things on the blog:

• Blog Extension,
• Gallery Extension,
• AdsenseKit Package.

(continue reading)

While I was reading my getting stated tutorial about MicroPython again, I noticed that I've forgotten to tell something about dependencies or packages.

Here is possible to find some MicroPython packages. On the WeMos or the ESP8266, it is possible to install these packages using the upip package manager. The WiPy doesn't have the package.

As I promised some photos of Bangkok (Thailand). Enjoy the photos!

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 RT-Preempt Patch 4.14.21-rt17!

There are a lot of tutorials for Raspberry Pi kernel patching using RT-Preempt, 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 kernel working, if it is kept updated.

Update: 18.03.2018: The repository is now here! It is a branch from the official Raspberry Pi kernel repository.

As I promised some photos of Melbourne (Australia). Bangkok photos are coming this week. I don't know if you noticed, but I added two new repositories to GitHub:

• AdsenseKit-ADS
• Extended Blog

Both repositories are extensions for PageKit. The first one allows you to add Google Adsense ads to the posts. The second one extends the PageKit blog plugin to add categories and tags to the blog posts. I was/am quite busy these weeks, but I am writing the README files. I need to check them again. Enjoy the photos!

Out with the old, in with the new! Happy 2018!

This time something without electronics. I took the title photo! You should read "Happy New Year" ;). Thanks to my brother who wrote it in the air! Nice!

As you may notice, I use his music on the videos. If you want to hear more great music, here you find the links:

• Sentimientos Sudamericanos
• Maxixe
• Youtube

It has been a while since my last post! Sorry, I was a little bit busy and then I was on a business trip in Melbourne for the CDC2017 and then I had a week holiday in Bangkok. I will be posting some photos on the next days!

It's been a year now since I started this blog. It's a hard job to maintain it up-to-date but I still have fun writing and coding for this purpose! So let us start!

The first video that I published a year ago was using the Wipy2.0 and a WS2812b led strip for some Christmas lights (click here). Now, this time I bought a WS2812b panel (100 bits or 10x10 pixels -or leds- see fig. 1) and as we have/had christmas again, so I wrote some code for this panel to make again some Xmas lights! :).

I will be testing the new release on this weekend!

The release notes seem promising!

I have also some new things with Docker and Raspberry Pi!

Stay tuned!