embedded-systems-study-group | Notes and Assignments of embedded systems study group

Coming from C/C++ background, I am aware of coding standards that apply for Safety Critical applications (like the classic trio Medical-Automotive-Aerospace) in the context of embedded systems , such as MISRA, SEI CERT, Barr etc.

Skipping the question if it should or if it is applicable as a language, I want to create Python applications for embedded systems that -even vaguely- follow some safety standard, but couldn't find any by searching, except from generic Python coding standards (like PEP8)

Is there a Python coding guideline that specificallly apply to safety-critical systems ?

I've been developing in C using eclipse as my IDE in my virtual machine with ubuntu, I've made some progress and I wanted to test them in the real product which is an embedded system using powerpc.

In order to compile that program for our product I use Code::Blocks in Windows but the compiler is a powerpc version of the gcc.

The same code is giving me an error in the powerpc version that doesn't appear in the ubuntu version.

I have two header files gral.h and module_hand.h as follows:

The gral.h file:

I'm working on some Linux embedded system at the moment and using Yocto to build Linux distribution for a board.

I've followed Yocto build flow:

• download layers sources
• build image
• flash image into the board or generate SDK.

Everything works great. However I was required to add some changes to local.conf, probably add some *.bbapend files, systemd services and so forth. So, I'm wondering how can save that local changes in case if I'll want to setup a new build machine or current one will be corrupted.

Should I create a custom image or layer that will inherit everything from a board manufacturer one and add changes and functionalities that are needed to me? Or something else?

I have a few large static arrays that are used in a resource constrained embedded system (small microcontroller, bare metal). These are occasionally added to over the course of the project, but all follow that same mathematical formula for population. I could just make a Python script to generate a new header with the needed arrays before compilation, but it would be nicer to have it happen in the pre-processor like you might do with template meta-programming in C++. Is there any relatively easy way to do this in C? I've seen ways to get control structures like while loops using just the pre-processor, but that seems a bit unnatural to me.

Here is an example of once such map, an approximation to arctan, in Python, where the parameter a is used to determine the length and values of the array, and is currently run at a variety of values from about 100 to about 2^14:

I'm trying to build libc6 with a custom prefix by modifying the prefix=/usr line in debian/rules. However, this fails because the patch is applied multiple times. Curiously, patching another file does not result in the same error. I've distilled the failure down to this script:

This is a time table, columns=hour, rows=weekday, data=subject [weekday x hour]

I need to run numpy in an embedded system that has an ARM SoC, so I cross-compiled Python 3.8.10 and Numpy using arm-linux-gnueabihf-gcc. Then I copied both executables and libraries to the embedded system. But when I try to import numpy I get the following error:

I am trying to write a special type handling for array data redundancy. The idea is to define and declare an array globally at compile time with fixed size, but the size is different to each declared array. This is the idea:

I am looking for an efficient way of pixel manipulation in python. The goal is to make a python script that acts as virtual desktop for embedded system. I already have one version that works, but it takes more than a second to display single frame (too long).

Refreshing display 5 times per second would be great.

How it works:

1. There is an electronic device with microcontroller and display (128x64px, black and white pixels).
2. There is a PC connected to it via RS-485.
3. There is a data buffer in microcontroller, that represents every single pixel. Lets call it diplay_buffer.
4. Python script on PC downloads diplay_buffer from microcontroller.
5. Python script creates image according to data from diplay_buffer. (THIS I NEED TO OPTIMIZE)

diplay_buffer is an array of 1024 bytes. Microcontroller prepares it and then displays its content on the real display. I need to display a virtual copy of real display on PC screen using python script.

How it is displayed:

Single bit in diplay_buffer represents single pixel. display has 128x64 pixels. Each byte from diplay_buffer represents 8 pixels in vertical. First 128 bytes represent first row of pixels (there is 64px / 8 pixels in byte = 8 rows).

I use python TK and function img.put() to insert pixels. I insert black pixel if bit is 1 and white if bit is 0. It is very ineffective. Meybe there is diffrent class than PhotoImage, with better pixel capability?

I attach minimum code with sample diplay_buffer. When you run the script, you will see the frame and execution time.

Meybe there would be somebody so helpful to try optimize it? Could you tell me faster way of displaying pixels, please?

denderdale

Sample frame downloaded from uC

And the code (you can easily run it)