Application program samples used in practice [useful for ARM electronic work]

May 23, 2020 April 18, 2022

Mechanotoro

Table of contents

1 Applications and Practices

Applications and Practices

In "Tutorial to ARM (STM32) Basics and Development", I have mainly explained the basics of the MCU peripherals, from the configuration of each peripheral to system design using MCU.

We will now use the teaching material board to create an actual application and check its operation.
The purpose of this course is to deepen your understanding by transferring actual programs to the teaching material board and checking their operation. First, let's learn the basics by running the program and then develop it into applications.

The educational board allows students to learn the functions of general-purpose I/O GPIOs, timers, AD converters, serial communication USART, and serial communication I²C while checking the actual hardware circuits.

When LED (with load resistor) and Pushbutton SW are connected as external components, general-purpose input/output applications can be created and operation can be checked. When a VR(variable resistor) is connected and an analog signal 0-5V is input, an application for AD conversion can be created and its operation checked.

In addition, a UART-USB conversion cable allows serial communication with a PC. If you want to check the numerical values of the imported data, you can use serial UART to display them on the PC screen.

In particular, once you are able to freely operate serial USART, you will be able to operate and monitor input/output from a PC, which can be developed into a variety of microcomputer applications, so please learn this at an early stage.

Let's try an application that uses a wireless LAN module to make Nucleo, a teaching material board, WiFi-enabled and IoT-enabled at the stage where you have finished learning the practical use of peripherals. For the wireless LAN module, we will use a module with ESP32, which is popular in electronic construction.

Furthermore, we would like to challenge applications for speed control and positioning control using motors equipped with encoders. Adding a sensor such as an encoder to a motor allows it to be developed into a motion control with advanced feedback control. This is the best way to check the basics of motion contro l where variable pulses are given as speed and position commands.

The possibilities for applications that can be developed using the Teaching Resource Board are endless. Depending on your ideas, you can realize quite a variety of things.

GPIO Applications

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STM32 Nucleo MCU starting with LED blinking [Gateway to Embedded system]

https://en.depfields.com/gpio-led-toggle-apl

Setting the STM32's peripheral GPIOs to blink the output LEDs is a simple operation in itself, but it means that the series of steps from the initial setup of MCU to the build and transfer to MCU have been successfully completed.The most elementary program for MCU is probably the LED-blinking, which arbitrarily turns on and off LEDs connected to the outputs.Although the operation itself is simple, controlling the output LEDs means that the series of steps from the initial setup of MCU us...

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GPIO ON-delay input application [GPIO practical example for STM32]

https://en.depfields.com/gpio-ondelay-apl

ON-delay inputAfter the successful "LED-blingking", I will introduce the application of anti-chattering on-delay input and unused pin processing examples to practical examples of STM32GPIO input.This program adds an on-delay input function and processing of unused pins to prevent chattering.Chattering is a mechanical vibration of the contacts that causes the switch to turn on and off at very short intervals when the switch is input.ChatteringAn ON-delay input is one that is turned O...

Timer/counter Applications

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Fixed pulse application [Pulse output of STM32]

https://en.depfields.com/tim-toggle-apl

This application program uses the timer of the STM32 MCU to generate a fixed frequency pulse only when an input switch is pressed.Timer output circuitSetting Specification：Pin used：PB8 Alternate output(Timer output)Peripheral used：TIM4_CH3 Counter CLK 1kHz This application uses CH3 of TIM4. The pin used is TIM4, the default alternate function of PB8.The TIM4 setting sets the timer count clock to 1 kHz and counts 500 to generate a 1 Hz pulse from CH3.

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PWM pulse application [PWM output of STM32]

https://en.depfields.com/tim-pwm-apl

This is an application program that sets the timer of the STM32 MCU to PWM output. You can see the frequency and pulse duty ratio change depending on the setting value.This is an application for pulse output using PWM (Pulse Width Modulation). The settings are the same as for the fixed pulse application, but the count clock is set to 1 kHz.For PWM output, a variable ARR_val of 1000 generates a 1 Hz pulse, resulting in LED blinking at 1 second intervals. In the case of PWM, the ARR cycle is t...

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Variable pulse application [Pulse control with STM32].

https://en.depfields.com/tim-variablefreq-apl

This application controls arbitrary frequency pulses with STM32 MCU. In this example, the frequency changes when a pushbutton switch is held down, but it can be applied in many other ways.This program changes the blinking cycle of the timer output by increasing or decreasing the counter setting value when the pushbutton switch input is turned ON.A 10 ms interrupt is generated by Systick and the counter set value (arr_val) is increased or decreased in the SysTick interrupt handler.Setting Spec...

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PWM dimming of LEDs with MCU [STM32 Nucleo]

https://en.depfields.com/led-dimming

How can we use the digital output of MCU to dim LEDs? I will explain the magic trick of using the digital output of MCU to control the brightness continuously in an analog manner, as if dimming were a magic trick.As an application of the timer, let's try dimming LED lights using the PMW output. Normally, LEDs can be turned on and off simply by switching MCU output ON/OFF, which is typical of digital outputs.How can we dim LEDs using the digital output of MCU? Using the digital output of ...

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Let's sound a piezoelectric buzzer and speaker [STM32 Nucleo]

https://en.depfields.com/buzzer-apl

Let's connect a piezoelectric buzzer and speaker to an STM32 MCU (Nucleo board) and play them. This time, I used an inexpensive piezoelectric buzzer (model: LF-MB12B06). This is an application of a peripheral timer. For details, see Timer/Counter .Piezoelectric buzzer specificationsA piezoelectric buzzer is a component with a built-in oscillation circuit that generates sound by resonance when a voltage according to specifications is applied. A piezoelectric speaker (sounder) is a similar...

SysTick interrupt Applications

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SysTick interrupt application [SysTick for STM32]

https://en.depfields.com/systick-it-apl

This is an application for interrupts using the SysTick timer provided in the ARM core without using peripherals.This is a program for blinking LEDs using Systick interrupts.The Systick timer generates an interrupt every second to switch the LED on and off.This program generates and processes interrupts using the system clock of 72 MHz divided by 8 as a systick timer.Within the interrupt handler SysTick_Handler, the program simply switches the toggle flag. In the main program, the output LED ...

External interrupts Applications

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External input interrupt application [EXTI for STM32]

https://en.depfields.com/ext-it-apl

This is an example of an interrupt application with an external input signal. The following is an explanation of the unique part of external interrupts. This is an application of the EXTI external interrupt for the STM32 MCU. This is an example of an application in which a pushbutton switch is used as an interrupt input to switch the output LED on and off. Interrupt inputs are sensitive, so care must be taken to prevent chattering when using them.Setting Spec.：Input ：PC13 Floating input Ou...

Serial communication USART Applications

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1 character send/receive application [USART of STM32]

https://en.depfields.com/usart-rxtx-char-apl

This is the simplest program for STM32 USART. The communication application is almost language-like outside of MCU knowledge because it deals with strings. It is a great way to familiarize yourself with arrays to store characters, the concept of pointers and addresses, etc.Let's start with a program that sends and receives a single character (1 byte) serially.Setting Spec. :Input : PC10 Floating inputOutput :PC11 Alternate Push-pull outputSerial connection diagramInsert delay...

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String send/receive application [USART of STM32]

https://en.depfields.com/usart-rxtx-string-apl

Since it is not practical to send a single character code in USART with the STM32 MCU, this application has been developed to send and receive a continuous string of characters. This is an example of an application that uses a pointer to store a continuous string of characters in a variable and send/receive it.In the previous article, we sent and received a single character, but actual communication handles strings of two or more characters; in USART serial communication, commands for sending...

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String interrupt receivie application [USART of STM32]

https://en.depfields.com/usart-rx-it-apl

This application uses receive interrupts in USART with the STM32 MCU. Compared to the polling method, it is more efficient because it can process only when receiving. This is an example of a ready-to-use application.This program receives strings from the PC via interrupt.Until now, this has been a polling process, periodically checking to see if a reception has occurred.MCU does not know when a string reception from the PC will occur. It is not efficient to perform polling processing for this...

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String Interrupt send application Part 1 [USART of STM32]

https://en.depfields.com/usart-tx-it-pointer-apl

This application sends strings via interrupt in USART with the STM32 MCU. This method is the simplest and easiest to understand, using a pointer to store the string in a variable while sending it, but it is limited to one type of string, and if several types of strings are sent, they interfere with each other.This program sends a string to the PC using interrupts and is valid only for sending one type of string. If you want to send another string in succession, it must be buffered as describe...

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String Interrupt send application Part 2 [USART of STM32]

https://en.depfields.com/usart-tx-it-buffer-apl

This is a buffered application that sends several types of strings in USART with the STM32 MCU without interfering with each other. The buffer is provided to perform multiple string transmissions without interference.Although one type of character could be sent by using the pointer to send a string, multiple strings cannot be sent due to interference.Therefore, each string can be sent without interference by storing each string to be sent in a buffer while sending.By making the pointers array...

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String interrupt send/receive application [USART of STM32]

https://en.depfields.com/usart-rxtx-it-buffer-apl

This is a program that uses a buffer for sending strings and interrupts for multiple strings, and also interrupts for receiving strings using STM32 USART.This is a practical program that performs interrupt processing for both sending and receiving and can send multiple character strings at arbitrary times.

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String DMA send/receive application [USART of STM32]

https://en.depfields.com/usart-rxtx-DMA-buffer-apl

This application uses STM32 USART DMA for sending and receiving character strings in serial communication. When character strings are long or the number of transfers is large, DMA is advantageous because it does not burden the CPU.This is a program for sending/receiving strings by DMA transfer.When several different strings are sent and received in succession, it is more stable for the strings to be of fixed length. Also, in transmission, with a string storage buffer, transmitted characters d...

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Serial Monitor [USART of STM32]

https://en.depfields.com/monitor-debug-apl

Debug programming using the USART of the STM32 MCU. Debugging is achieved by inserting microcontroller-specific tsprintf statements that display numerical values at arbitrary points in the program and displaying the data using general-purpose terminal emulator on a PC.めかのとろIntroducing a serial monitor application for monitor debugging, which is useful for identifying the data of calculation results inside a program, branch locations, etc.めかのとろIt is based on sending a string (buffere...

ADC Applications

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On demand ADC application [ADC of STM32]

https://en.depfields.com/adc-single-apl

This program displays the data acquired by manually starting AD conversion of the 1-channel analog input signal of the STM32 ADC each time it is needed.Numerical data of analog voltage taken from PA0 is converted to character strings for display and sent serially to a PC for monitoring.In this circuit, the output impedance should be a little larger, depending on the resistance of the volume.Serial communication for monitors is the simplest, pointer-style string transmission without interrupts...

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Continuous ADC application [ADC of STM32]

https://en.depfields.com/adc-continuous-apl

This program automatically and continuously converts and displays the 1-channel analog input signal from STM32 ADC. Since this is a continuous conversion mode, once set, the conversion value can be obtained at any desired timing.This program automatically and continuously converts and displays 1-channel analog input signals.In the case of the case of each time conversion, the analog conversion is performed only at the timing when the analog value is to be acquired, so a wait time is generate...

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Continuous ADC application with completion interrupt [ADC of STM32]

https://en.depfields.com/adc-continuous-it-apl

This program is an introduction to the combination of AD conversion and interrupts; interrupts are supposed to be generated each time AD conversion is completed, and as it is, the frequency of interrupts is too high to be practical, but please understand interrupts as a learning tool.This program generates an interrupt when AD conversion is completed, acquires the conversion value in the process in the interrupt handler, and monitors and displays the acquired value in 100ms cycles The interru...

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Multi-channel continuous ADC (DMA) application [ADC of STM32]

https://en.depfields.com/adc-dma-apl

This is a practical application that automatically converts multiple channels of analog signals in succession on an STM32 MCU and retrieves them into memory. Please understand it completely and make use of it by all means.So far I have dealt with AD conversion of a single channel.This section describes a program that registers multiple channels into a regular conversion group to read the analog voltages input to pins PA0 and PA1 and then transfers them to memory by DMA. To convert the an...

Serial communication I2C Applications

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I2C communication application [I2C of STM32]

https://en.depfields.com/i2c-eeprom-apl

This application program reads and writes to the I2C specification type EEPROM of STM32 MCU. Details of the peripherals are explained in Serial Communication I2C.I2C EEPROM circuit diagramHere PB10 and PB11 are used for I2C2. Data read from memory is transferred to the monitor using USART3 for display.The chip address of the I2C EEPROM is A0 because A0, A1, and A2 are set to 0 V as shown in the above figure. Please refer to the I2C EEPROM 24LCxx datasheet for details.Three data (data1, data2,...

Serial communication SPI Applications

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SPI communication application[SPI of STM32]

https://en.depfields.com/spi-eeprom-apl

Application program to read and write to SPI specification EEPROM. Details of the peripherals are explained in Serial Communication SPI.For I2C communication, the address is specified in the chip select, but for SPI communication, the chip select signal CS is given (to a "L" level) for each communication.Commands for writing to and reading from SPI EEPROMs are defined with #define at the beginning of the program. Refer to the data sheet of each EEPROM for the contents.SPI EEPROM cir...

RTOS Applications

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Multitasking by registering multiple tasks [STM32 and FreeRTOS]

https://en.depfields.com/rtos-multitask-apl

This is a sample program to execute two registered tasks simultaneously. Using RTOS, it is easy to execute completely different processes at the same time. As shown in the sample program, the RTOS can be easily executed with a simple description.Using an RTOS, it is easy to have completely different processes running simultaneously. It would be almost impossible and a waste of time to do the same thing without an RTOS, which, as shown in the sample program, can be done very easily with a s...

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Switching between multiple tasks, Part 1 [STM32 and FreeRTOS]

https://en.depfields.com/rtos-task-switch1-apl

This is a sample program that switches between two tasks with an external switch. A dedicated task is provided to manage the switching.The registered Task A and Task B processes have different LED blinking patterns, but the pushbutton switch input or not switches between Task A and Task B.Execute switch task, create a dedicated task C as so called task management, and switch between task A and task B according to the input of the switch.When I register a task, I create it with vTaskCreate().v...

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Switching between multiple tasks, Part 2 [STM32 and FreeRTOS]

https://en.depfields.com/rtos-task-switch2-apl

This is a sample program that combines task switching and USART communication, and manages task execution and suspension based on whether or not the command code given externally matches.This is a program that sets command codes for task switching in advance and executes the task specified by the command code and stops other tasks when the externally given code matches.Task switch by commandThis time, instead of using an input switch, a command is used to switch between Task A and Task B. The...

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Queue-based application [STM32 and FreeRTOS].

https://en.depfields.com/rtos-queue-apl

This application combines a task and a queue. This program is not practical, but it is a sample program for learning to understand the concept of queues in an easy-to-understand way.In the initial setting, xQueue = xQueueCreate(16, sizeof (int8_t)) is executed to allocate 16 queues.In the first task, the command ("start@") is entered and 10 queues are passed sequentially when the conditions for establishment are met. The cycle time of the task is set short at 10 ms.The second task d...

Measurement Applications

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Encoder speed measurement [STM32 Nucleo]

https://en.depfields.com/pulse-speed

The STM32 timer has the ability to measure external pulses. Encoders are often used as sensors to detect the position and speed of actuators such as robots, etc. This section introduces a method to measure pulses that vary with rotation speed from encoders.Pulse rate is the number of counts per unit of time, so it is sufficient to use a function that can count external pulses.The encoder used in this application is an open collector output type specification. The open collector output is a ty...

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Encoder position measurement [STM32 Nucleo]

https://en.depfields.com/pulse-position

The STM32 timer has a function to count up and down using encoder 2-phase output pulses as input. This section explains how to use this function to measure the amount of motor rotation from the reference position by up-down counting the pulses from the rotary encoder.With this function, for example, the pulses from an encoder directly connected to the motor shaft can be preset as the reference position at the start of measurement and then counted up and down to determine the amount the motor ...

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Heart rate monitor using pulse sensor and STM32 Nucleo

https://en.depfields.com/heartbeat

Try an application that counts the pulse, which is a slow pulse, and displays the heart rate per minute. Creating a pulse rate sensor using a photo reflector and operational amplifierThis section provides an explanation of an application that counts pulses and displays heart rate. The application to realize the heart rate application includes a good balance of elements necessary for learning, such as knowledge of analog electronic circuits, GPIO of the STM32 MCU, interrupts and serial commun...

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Thermometer using STM32 Nucleo

https://en.depfields.com/thermometer-apl

I will create an application to realize a thermometer using an inexpensive thermistor as a sensor element with an STM32 MCU (Nucleo board). It is a simple program, but it can be developed into various other arithmetic applications using floating point arithmetic with the Cortex-M3 core MCU.Thermistors are elements whose resistance changes with temperature, and those with NTC characteristics are suitable for thermometers. The NTC thermistor has a resistance value that decreases slowly as the t...

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Accelerometer using STM32 Nucleo

https://en.depfields.com/accel-apl

What is an Accelerometer?Among various sensors, accelerometers are often used in invisible places in products, so many people may not know what they are, despite their high utilization.For example, it is used in smartphones to change the orientation of the screen by detecting the tilt based on gravity applied to the internal acceleration sensor, and in pedometer applications that measure vibrations.The accelerometer used in this project is the Kinox KXTC9-2050, which can detect acceleration...

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Graphing and collecting sensor data via serial communication on STM32 MCU

https://en.depfields.com/datalogger

When creating applications, it is often necessary to collect digital data such as sensor data captured by MCU while graphing it in real time like an oscilloscope. We introduce an easy-to-use data logger that can import data into Microsoft Excel while displaying the data on a PC monitor using serial communication. What is a data logger application?Until now, sensor data and other data captured by MCU via serial communication and other means have been output to a PC or other monitor for d...

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Posture detection by accelerometer and gyro sensor [STM32Nucleo]

https://en.depfields.com/accel-gyro

The GY-521 Sensor Board with Accelerometer and Gyro Sensor (MPU-6050) can easily acquire 3-axis acceleration and 3-axis gyro data via I2C interface, and is recommended for its high information content and low cost.However, most of the information on the Internet is for Arduino, and while the programming can be easily utilized by anyone using existing library functions and can be made to work without understanding the specifications, it is not a skill that can be acquired because it can be use...

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Let's clarify the mechanism of the complementary filter [acceleration/gy...

https://en.depfields.com/complementary-filter

Complementary filters are often used to combine accelerometers and gyroscopes, but there are few explanations on the details of these filters. It is interesting to know how the complementary filter equation is derived and what the equation means. I will explain the calculation process to show that there is a deep meaning in a relatively simple formula.Accelerometer and gyro-sensors are devices that detect information on the motion and rotation of an object, but each has its own disadvantages ...

IoT Applications

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TCP communication (WiFi) send of STM32 with ESP32

https://en.depfields.com/esp32-tcp-tx-apl

This section introduces an application that uses the ESP32 wireless module to make Nucleo (STM32) wireless (WiFi) and send strings to a terminal on a PC or smartphone as a TCP server. The wireless module ESP32 is explained in detail in "ESP32 makes STM32Nucleo easily WiFi-enabled".The application introduced here is a basic one that sends strings from Nucleo (STM32), which is WiFi enabled with ESP32 and configured as a TCP server, to a terminal on a client PC or smartphone, but once ...

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TCP communication(WiFi) receive of STM32 with ESP32

https://en.depfields.com/esp32-tcp-rx-apl

Nucleo(STM32) is converted to wireless(WiFi) using the ESP32 wireless module and configured as a TCP server. I will introduce an application that remotely controls MCU by sending a string of command codes from a terminal emulator on a PC or smartphone. For more details about the ESP32 wireless module, see "ESP32 makes STM32Nucleo easily WiFi-enabled". Configure a TCP server and connect to it with a PC, smartphone, or other client terminal application. The same as "TCP communi...

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Send from WiFi enabled STM32 with ESP32 to web browser

https://en.depfields.com/esp32-http-tx-apl

This section introduces an application that uses the ESP32 wireless module to put Nucleo (STM32) into wireless (WiFi) mode and send strings to a terminal on a PC or smartphone as a web server. The details of ESP32 and browser settings and sending/receiving are explained in "Remote control of WiFi enabled STM32Nucleo with ESP32 using a browser". The application introduced here is a basic one that sends strings from Nucleo (STM32), which is WiFi enabled with ESP32 and configured as a...

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Operating the STM32 with ESP32 WiFi from a browser

https://en.depfields.com/esp32-http-rx-apl

Nucleo (STM32) is converted to wireless (WiFi) using the ESP32 wireless module and configured as a web server. We will introduce an application that remotely operates MCU by sending a string of command codes from a web browser on a client PC or smartphone. The details of setting up the ESP32 and browser and sending/receiving commands are explained in "Remote Remote control of WiFi enabled STM32Nucleo with ESP32 using a browser".Points to keep in mind when configuring a web serverTh...

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Why recommend STM32 Nucleo instead of Arduino for beginners in microcontrolle...

https://en.depfields.com/nucleo

For those who are aiming to become embedded engineers, I will introduce the recommended and best way to start learning in earnest, considering what kind of educational materials will help you acquire truly useful skills efficiently and in a short period of time.Here I will compare the Arduino, which is all the rage in electronics construction, with Mbed, ARM's open source development environment, and the STM32CubeIDE development environment customized to use the Nucleo MCU board we will ...

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