If you find yourself reading AUTOSAR document Specification of CRC Routines you are probably looking for a solution on how to implement it in your code. This is short instruction without explaining how CRC works. It includes working CRC code with examples from the mentioned documentation. Explanation of CRC8 CRC 8 it means, the polynomial of CRC is 8 bit long. Explaining chapter 7.2.1: CRC result width - it is the return value, it says it is 8 bits long Polynomial - this value is used to calculate CRC. In this case, it is 0x1D Initial value - CRC calculation start with this value. It is usually all F's or zeros. Input data reflection - it says if the data which you want to do CRC need to be reflected or not. Example of data reflection: hex: 0x73 or binary: 1110011, reflected value is: 1100111 or hex 0x67 Result data reflected - same as input data, but the only result is reflected XOR value - result value need to be XOR-ed with this value before...
This is a short tutorial that will explain how to build PX4 Autopilot, flash and debug it at the PX4 FMU (Flight Management Unit) without a debugger. Everything in this tutorial is tested and reproduced at Kubuntu 22.04 LTS (It works the same for Ubuntu as well). Preparation Let's start with cloning PX4 Autopilot > git clone https://github.com/PX4/PX4-Autopilot.git After the repository is cloned make sure you initialize all submodules. You would like to keep using this GIT commands when you jump between branches in PX4, otherwise, you can experience issues like missing modules while building. > cd PX4-Autopilot > git submodule sync > git submodule update --init --recursive And that is it we are almost ready to build our PX4 firmware. You need to know what board (FMU) you possess. Let's guess you have Pixracer. Pixracer is fmu-v4 board. Figure 1 - px4_fmu-v4 board source tree
ImmersionRC recently pushed out the new product known as Ghost. It is based upon LoRaWAN which gave it some nice advantages in comparison to other existing radios. ImmersionRC also created a new lightweight protocol to improve latency and some new features. This post will be more about how it is integrated into Betaflight code. At the moment of the writing the code is located here: https://github.com/betaflight/betaflight/blob/master/src/main/rx/ghst_protocol.h https://github.com/betaflight/betaflight/blob/master/src/main/rx/ghst.h https://github.com/betaflight/betaflight/blob/master/src/main/rx/ghst.c If you figure out how this protocol works you can use it in your projects. With Ghost radio transmitter and Ghost receivers, you can communicate with any device you want at a distance of around 10 km with very low latency including telemetry data. In the text below I'll describe how Ghost's frames look like. We are looking from the receiver's perspective (Betaflight flight c...
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