[Python / C] I made a device that wirelessly scrolls the screen of a PC remotely.


When practicing comics with friends, I display the lines on the computer in front of me and use it as a competition. If you display the characters in large size, you cannot see all the lines without scrolling. Therefore, I made a device that can scroll the screen of a personal computer up and down remotely.

System configuration

I thought of a system in which a PC scrolls when a switch attached to the controller at hand is pressed.

The configuration of the entire system is as follows.


The details of the above system overview are shown below. (Because it is not only practical but also intended to be made as part of study, I chose it with the intention of using various devices.)

  1. Sender --Microcomputer: ATtiny2313 --Microcomputer write writer: AVRISP mkⅡ
  1. Receiving side --Microcomputer: Arduino Micro
  1. PC side

After that, I will not touch on it in this article, but I used the following as a communication debugging tool such as serial transmission and reception.

--USB / serial converter: MR-USBSIR-F --Terminal: TeraTerm

In addition, the wireless module by Bluetooth has the transmitting side (SBDBT) as the slave and the receiving side (rn42xvp-i / rm) as the master. The reason is that SBDBT is a slave by default, and a write writer for the microcomputer (PIC24FJ64GB004-I / PT) is required to change to the master. On the other hand, since the setting of rn42xvp-i / rm can be changed simply by sending a command from a terminal such as Arduino's serial monitor or TeraTerm, the setting of rn42xvp-i / rm on the sending side was changed and used as the master. (Details of setting will be described later)

I thought ... but rn42xvp-i / rm seemed to be the master by default. However, even if you think about it without it, you can easily change the settings and it is convenient, so I used rn42xvp-i / rm as the master.

Receiver wireless module: rn42xvp-i / rm settings

As mentioned above, the setting of the wireless module on the transmitting side cannot be changed without a pic writer, so rn42xvp-i / rm on the receiving side was used as the master. By changing the setting of rn42xvp-i / rm in advance by sending a command from the terminal, it is possible to connect Bluetooth modules.

The procedure is shown below. You can do it from the serial monitor of Arduino IDE or from TeraTerm. When executing from the serial monitor of Arduino, execute after writing the following.


#include <SoftwareSerial.h>

#define BT_RX 8
#define BT_TX 7
#define BPS 115200 // rn42xvp-i/rm default baud rate

SoftwareSerial btSerial(BT_RX, BT_TX); //Serial settings for interacting with Bluetooth

void setup()
  Serial.begin(BPS); // PC -Initialization of serial communication between Arduino
  btSerial.begin(BPS); // Arduino -Initialization of serial communication between Bluetooth

void loop()
  //Transmission process from Arduino to Bluetooth
  if (Serial.available())
//    btSerial.write(Serial.read()); //Also OK here]

  //Signal reception processing from Bluetooth
  if (btSerial.available())
//    Serial.write(btSerial.read()); //Also OK here

In addition, I referred to the following article for implementation. ・ Http://workpiles.com/2014/04/rn42-bluetooth1/ ・ Htp: // Kosakai. Rld. Kokan. jp / R-42. html

The setting procedure is as follows.

number command new line response meaning
1 $$$ None CMD Command mode start
2 SA,0 Yes AOK Changed no authentication required for connection
3 SU,96 Yes AOK Change baud rate to 9600
4 R,1 Yes Reboot! Reboot the module (this will reflect the configuration changes)

What I made (hardware)

    1. Sender (ATtiny2313)

I thought about what to use as a base, but ordinary plastic plates and universal plates Since it is difficult to process, we used a 5 mm thick foamed styrene board that is relatively rigid and easy to process. The foamed styrene board was processed to an appropriate size, and a battery box and a board were attached.



  1. Receiving side (Arduino Micro)

The receiving side may be directly connected to a personal computer, so I created it on a breadboard.


source file

    1. Sender (ATtiny2313)


#include <avr/io.h>
#include <util/delay.h>
#include <avr/interrupt.h>
#define OFF 0   //For switching
#define ON  1   //Same as above
#define READ  0 //For port register setting
#define WRITE 1 //Same as above
#define CNTD  0 //Used to measure the time the switch is held down
#define CNTU  1 //Same as above
#define KRTIME 100000 //Time to hold down the switch to be recognized as being pushed

void AVR_init(void)
	//Settings such as serial communication

void USART_init(void)
	unsigned int baud;
	baud=8000000/16/9600-1;          //Baud rate calculation(The calculation formula is the specification P.75 Listed at the bottom)
	UBRRH=(unsigned char)(baud>>8);  //Baud rate setting(Upper byte)
	UBRRL=(unsigned char)baud;       //Baud rate setting(Lower byte)
	UCSRC=(0<<USBS)|(3<<UCSZ0);      //Set the used bit length to 8 bits and the stop bit to 2 bits
	UCSRB=(1<<RXEN)|(1<<TXEN);       //Send / receive permission

void Utx(char *data) //Data transmission
	int i;
	//Terminated character "\Loop to "0"
	for(i=0; data[i]!='\0'; i++)
		while(!(UCSRA & (1<<UDRE)) );

void INT_init(void)
	//INT0 and 1(Pins 6 and 7)Allow interrupts
	GIMSK=0b11000000; //General interrupt enable register
	MCUCR=0b00001111; //Set external interrupt trigger on the up edge for both INT0 and 1
// 	SREG=0b10000000;  //Multiple interrupts disabled → Disabled by default

ISR(INT0_vect) //Pin 7 interrupt handler
	//Chattering measures

	Utx("_");  //Terminated character

ISR(INT1_vect) //Pin 6 interrupt handler
	//Chattering measures

	Utx("_");  //Terminated character

unsigned char Urx(void) //Data reception
	while(!(UCSRA & (1<<RXC)) );
	return UDR;

int main(void)
	//Key repeat(Hold down the switch)Time measurement
	static unsigned long rptcnt[1] = {}; //Since int became 2 bytes, declare it as long
	sei(); //All interrupt enable instructions
	PORTD=ON<<PD6; //Always 5V output(For switching)

		//Correspondence processing to hold down the button
		if (bit_is_set(PIND, 4)) //When PD4 is 1 (pressing the button)
			if (rptcnt[CNTD] > KRTIME) //Detects holding down
				Utx("_"); //Terminated character
			else //Add key repeat time
		else if (bit_is_set(PIND, 5)) //When PD5 is 1 (pressing the button)
			if (rptcnt[CNTU] > KRTIME) //Detects holding down
				Utx("_"); //Terminated character
			else //Add hold time
		else //Clear the holding time to zero
			rptcnt[CNTD] = 0;
			rptcnt[CNTU] = 0;
			// memset(rptcnt, 0, sizeof(rptcnt)*10); //Do not use because it depends on the processing system
  1. Receiving side (Arduino Micro)


#include <SoftwareSerial.h>

#define BT_RX    8 // Arudino-Used for serial communication between Bluetooth
#define BT_TX    7 //Same as above
#define BAUD  9600 //Serial communication baud rate
#define OUT_5V   2 //Pin number
#define IN_5V    3 //Same as above
#define LED_OUT  4 //Same as above
#define BUFF_MAX 5 //Capacity of serial reception buffer (unit: characters)

// Arudino-Software serial settings between Bluetooth
SoftwareSerial btSerial(BT_RX, BT_TX);

void setup()
  pinMode(OUT_5V, OUTPUT); //Used for switching
  pinMode(IN_5V,  INPUT);  //Same as above

void init_bt() //Connection with Bluetooth module
  btSerial.print("$$$"); //Transition to setting mode
  btSerial.print("C,00198600035E\n"); //Connect to other bluetooth modules
  btSerial.print("---\n"); //Exit command mode if connection fails (ignored on success)

void loop()
  char buff[BUFF_MAX]={'\0'};
  static int cnt = 0;
  digitalWrite(OUT_5V, HIGH); //Always 5V output (for switching)

  //Bluetooth connection after pressing the switch
  if (digitalRead(IN_5V))

  //Transmission process to Bluetooth module (used when transmitting from serial monitor)
  if (Serial.available())

  //Receive processing from Bluetooth module
  if (btSerial.available())
    //Send the received value to the PC side
    Serial.print(btSerial.readStringUntil('_')); //Use Until because readString is slow (argument is terminating character)
    1. PC side (only this is Python)


import serial
import re
import pyautogui as pgui

def ctrl_screen():  # 0.Perform processing at 08sec intervals
    with serial.Serial('COM8', 9600, timeout=0.08, stopbits=serial.STOPBITS_TWO) as ser:

        while True:
            val = ser.readline()
            val = val.decode() #Convert bytes type to str type (unicode string)

            if val == 'UP':
                pgui.typewrite(['up'])  #Scroll up the screen
            elif val == 'DOWN':
                pgui.typewrite(['down'])  #Scroll down the screen

if __name__ == "__main__":



The circuit diagram of this system is shown below. I used draw.io for drawing. I wrote a circuit diagram for the first time, but it's free, easy to write, and convenient!

    1. Sender (ATtiny2313)


  1. Receiving side (Arduino Micro)


How to use

    1. Start the Python script on the PC side.
  1. Turn on both the master and slave. (Master only connects to PC)

    1. Press the switch on the master side to connect the Bluetooth modules. If the connection is successful, the blinking LED will be lit. Now ready image.png
  2. Press the switch on the slave side to scroll the PC screen up and down. image.png

Precautions for implementation

If you change the setting of ATtiny2313 to use an external crystal oscillator, of course, if you do not attach an external crystal oscillator, the microcomputer will not work or even write. An internal oscillator is enough! If you set it to use an external oscillator without an oscillator, you will not be able to do anything without an external oscillator (I am).

Also, when using the software serial library with Arduino, there are restrictions on the pins that can be used. Details below ↓ https://garretlab.web.fc2.com/arduino_reference/libraries/standard_libraries/SoftwareSerial/

Information that was used as a reference

In addition to the sites mentioned so far in this article, the following sites have been indebted. Thank you very much.

Contents Link destination
Basic usage of ATtiny2313 http://lumenbolk.com/?p=19
Solution for error caused by "import serial" https://teratail.com/questions/101843
PC(Python)Serial communication between and ardino https://qiita.com/Acqua_Alta/items/9f19afddc6db1e4d4286
Kbhit in Arduino()Usability of https://forum.arduino.cc/index.php?topic=294636.0
How to detect key event in Arduino https://www.quora.com/How-do-I-detect-a-keyboard-event-in-an-Arduino-IDE-program
Key operation method by Python https://www.lisz-works.com/entry/pyautogui-key
Key operation method by Arduino https://garretlab.web.fc2.com/arduino_reference/language/functions/usb/keyboard/write.html
How to receive character strings in Arduino serial communication https://ch.nicovideo.jp/yugata/blomaga/ar1177727


It's better to do this here ... or something wrong here! If you have any questions, sorry to trouble you, but if you can point it out, I will be happy to shed tears.

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