C++ REST SDK

C++ REST SDK is for cloud based client server communication using C++ API design [1].

• Setting up
• Simple GET Client
• POST Client
• CppREST Server
• GUI Multithreaded Examples

Cross Compiling C++ Programs for Raspberry Pi that Uses Static or Shared Libraries Such as OpenCV and wxWidgets

In this article, cross compiling C++ programs for Raspberry Pi on Ubuntu Linux system is discussed. We use "schroot" to avoid messing the main system and to get clean build environment.

• Setting up
• Using schroot
• Building a Simple Program
• OpenCV
• wxWidgets

Using Orange Pi

Orange Pi is a cheap alternative to Raspberry. They can be bought at their online store Shenzhen Xunlong at Aliexpress. There are many Orange Pi models. For example, Orange Pi One costs only ~USD 10. Another model called Orange Pi PC Plus even has 8 GB eMMC onboard and costs ~USD 25 only.

Figure. Orange Pi One

• Setting Up
• Desktop
• eMMC
• VNC Server
• Linux Headers
• GPIO

Tesseract OCR with C++, OpenCV, and wxWidgets

Tesseract is a free optical character recognition software and it is considered one of the most accurate open-source OCR engines [1].

• Installation on Ubuntu
• Using tesseract command
• Tesseract C++ API with OpenCV
• With wxWidgets

Getting Started with FRDM-K64F

To use FRDM-K64F with the latest MCUXpresso IDE, you need to update the firmware for its debugger. It is similar to FRDM-K82F where the details can be seen at the following post.

http://cool-emerald.blogspot.com/2020/01/getting-started-with-frdm-k82f.html

There are only a few minor difference between FRDM-K64F and FRDM-K82F to get started. Therefore, I will only list some major points here.

Figure. FRDM-K64F board

Original OpenSDA appears as MBED drive. And it is not working with MCUXpresso. To update the firmware for its debugger,

• Disable 'Windows storage services' ( https://os.mbed.com/blog/entry/DAPLink-bootloader-update/)
• Hold reset button and connect the device to a USB port. It should now appear as a drive called BOOTLOADER
• Drag and drop bootloader ‘0244_k20dx_bootloader_update_0x5000.bin’ into the drive.
• Remove and reconnect without holding reset. Board shows as ‘MAINTANCE’.
• Drag and drop Segger jLink OpenSDA for board specific firmware for K64F (‘02_OpenSDA_FRDM-K64F.bin’) which is available at https://www.segger.com/downloads/jlink#JLinkOpenSDABoardSpecificFirmwares
• Remove and reconnect without holding reset button. It now appears as ‘FRDM-K64FJ’
• To use JLink , open cmd and enter
  
  

  > cd "C:\Program Files (x86)\SEGGER\JLink"
  > JLink.exe -speed auto -device 'MK64FN1M0xxx12' -if SWD
  

  
  
  
• At the JLink prompt
  
  

  J-Link> r
  J-Link> erase
  J-Link> q
  

  
  
  
• After that, it should be OK to use MCUXpresso

ADS1115 ADC

ADS1115 is a precision, low power, 16 bit 860 SPS I2C analog to digital converter (ADC). It has internal reference, oscillator, and programmable comparator. ADS1115 modules are readily available at online markets like AliExpress and Adafruit

Figure 1. ADS1115 Adafruit module
( learn.adafruit.com/adafruit-4-channel-adc-breakouts/downloads).

Working with JSON in C++

In this article, using JsonCpp library and wxJson library to work with JSON (JavaScript Object Notation) in C++ is discussed.

• JsonCpp
• wxJson

JsonCpp

A convenient way to use JsonCpp is adding its amalgamated source. At first, get the source from the official repository,

https://github.com/open-source-parsers/jsoncpp,

by entering the following command.

$ git clone https://github.com/open-source-parsers/jsoncpp.git

Multithreading with wxWidgets

In this article, the use of multithreading with wxWidgets is discussed using C++ example programs. The following usage examples are discussed and detailed explanations for each of the step and function of using multhreading are presented.

• Simple Multithreading
• Using Events
• Using GUI from a Thread

A basic multithreading example, and the result of running the program is shown in the following link and the figure.

https://github.com/yan9a/cewx/blob/master/thread/thread1/thread1.cpp

Figure 1. thread1.cpp

Simple Multithreading Example

As a simple multithreading example, the program at the following link is discussed.

https://github.com/yan9a/cewx/blob/master/thread/th-simple/th-simple.cpp

Firstly, start, stop, pause, and resume buttons are added. Start button is used to create and start a new thread. Clicking the 'Stop' button looks for the last created thread and delete it. Pause button is used to pause the last started thread. Resume button is used to look for the last paused thread and run it.

Linux Device Driver on Raspberry Pi

In this article, I would like to discuss developing a IO device driver for Linux. Although, I use a Raspberry Pi as an example, it should work on other Debian based Linux systems too.

• Kernel Headers
• Driver
• Digital IO

Identification and Compensation of Hysteresis Using Discrete Backlash Operator

In this article, I would like to present about 'A Discrete Backlash Operator for Identification and Compensation of Hysteresis and Non-linearity for Piezoelectric Actuator' and its practical implementation in MatLab and LabView. The authors, Yan Naing Aye and Ang Wei Tech, are with School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798. yan9aye@gmail.com, WTAng@ntu.edu.sg .

The paper in PDF format and the implemented code in MatLab and LabVIEW are available at

https://yan9a.github.io/DiscreteBacklashOperator/yan-naing-aye-wytu-icstsd-2018.pdf

and

https://github.com/yan9a/DiscreteBacklashOperator

Abstract

A new invertible digitized model called Discrete Backlash Operator is proposed to model complex hysteretic nonlinearities. A discrete backlash operator is formed by combining multiple elementary virtual gears called discrete backlash gears. A discrete backlash operator with n discrete backlash gears has 2 power n possible states. The inverse model of discrete backlash operator is also developed for a feedforward controller to control the piezoelectric actuator.

Getting Started with FRDM-K82F

FRDM-K82F is a low cost development platform using MK82FN256VLL15 microcontroller. When I started using the board according to its getting started guide at

Get Started with the FRDM-K82F [NXP16],

I found out that its out-of-box demo is not running on my version of FRDM-K82F board. The insturctions on that page are also out of date. And, I could not get it worked.

After spending my time testing, browing the Internet, and experimenting, I found out that the following things might be necessary, in a brief, to make the board worked.

• Debug adapter - update it
• IDE - use MCUXpresso instead of Kinetis Studio
• SDK - use MCUXpresso SDK Builder (make sure to 'drag and drop')
• Flash - unlock the MCU's flash if required

Figure. FRDM-K82F board.

PCF8591 - 8-bit A/D and D/A converter

PCF8591 is an ADC/DAC device with four analog inputs and one analog output. It has an I2C interface with three address pins. The operating supply voltage range is from 2.5 V to 6.0 V. When all three address pins are low, its address is 0x48.

Figure. PCF8591 pins.