3.1.1 Counting Device

Introduction

Here we will make a number-displaying counter system, consisting of a PIR sensor and a 4-digit segment display. When the PIR detects that someone is passing by, the number on the 4-digit segment display will add 1. You can use this counter to count the number of people walking through the passageway.

Components

_images/list_Counting_Device1.png _images/list_Counting_Device2.png

Schematic Diagram

T-Board Name

physical

wiringPi

BCM

GPIO17

Pin 11

0

17

GPIO27

Pin 13

2

27

GPIO22

Pin 15

3

22

SPIMOSI

Pin 19

12

10

GPIO18

Pin 12

1

18

GPIO23

Pin 16

4

23

GPIO24

Pin 18

5

24

GPIO26

Pin 37

25

26

_images/Schematic_three_one1.png

Experimental Procedures

Step 1: Build the circuit.

计数器_bb

For C Language Users

Step 2: Go to the folder of the code.

cd /home/pi/davinci-kit-for-raspberry-pi/c/3.1.1/

Step 3: Compile the code.

gcc 3.1.1_CountingDevice.c -lwiringPi

Step 4: Run the executable file.

sudo ./a.out

After the code runs, when the PIR detects that someone is passing by, the number on the 4-digit segment display will add 1.

Note

If it does not work after running, or there is an error prompt: “wiringPi.h: No such file or directory”, please refer to C code is not working?.

Code Explanation

void display()
{
    clearDisplay();
    pickDigit(0);
    hc595_shift(number[counter % 10]);

    clearDisplay();
    pickDigit(1);
    hc595_shift(number[counter % 100 / 10]);

    clearDisplay();
    pickDigit(2);
    hc595_shift(number[counter % 1000 / 100]);

    clearDisplay();
    pickDigit(3);
    hc595_shift(number[counter % 10000 / 1000]);
}

First, start the fourth segment display, write the single-digit number. Then start the third segment display, and type in the tens digit; after that, start the second and the first segment display respectively, and write the hundreds and thousands digits respectively. Because the refreshing speed is very fast, we see a complete four-digit display.

void loop(){
    int currentState =0;
    int lastState=0;
    while(1){
        display();
        currentState=digitalRead(sensorPin);
        if((currentState==0)&&(lastState==1)){
            counter +=1;
        }
        lastState=currentState;
    }
}

This is the main function: display the number on the 4-digit segment display and read the PIR value. When the PIR detects that someone is passing by, the number on the 4-digit segment display will add 1.

For Python Language Users

Step 2: Go to the folder of the code.

cd /home/pi/davinci-kit-for-raspberry-pi/python/

Step 3: Run the executable file.

sudo python3 3.1.1_CountingDevice.py

After the code runs, when the PIR detects that someone is passing by, the number on the 4-digit segment display will add 1.

code

Note

You can Modify/Reset/Copy/Run/Stop the code below. But before that, you need to go to source code path like davinci-kit-for-raspberry-pi/python.

import RPi.GPIO as GPIO
import time

sensorPin = 26

SDI = 24
RCLK = 23
SRCLK = 18

placePin = (10, 22, 27, 17)
number = (0xc0, 0xf9, 0xa4, 0xb0, 0x99, 0x92, 0x82, 0xf8, 0x80, 0x90)

counter = 0

def clearDisplay():
    for i in range(8):
        GPIO.output(SDI, 1)
        GPIO.output(SRCLK, GPIO.HIGH)
        GPIO.output(SRCLK, GPIO.LOW)
    GPIO.output(RCLK, GPIO.HIGH)
    GPIO.output(RCLK, GPIO.LOW)

def hc595_shift(data):
    for i in range(8):
        GPIO.output(SDI, 0x80 & (data << i))
        GPIO.output(SRCLK, GPIO.HIGH)
        GPIO.output(SRCLK, GPIO.LOW)
    GPIO.output(RCLK, GPIO.HIGH)
    GPIO.output(RCLK, GPIO.LOW)

def pickDigit(digit):
    for i in placePin:
        GPIO.output(i,GPIO.LOW)
    GPIO.output(placePin[digit], GPIO.HIGH)

def display():
    global counter
    clearDisplay()
    pickDigit(0)
    hc595_shift(number[counter % 10])

    clearDisplay()
    pickDigit(1)
    hc595_shift(number[counter % 100//10])

    clearDisplay()
    pickDigit(2)
    hc595_shift(number[counter % 1000//100])

    clearDisplay()
    pickDigit(3)
    hc595_shift(number[counter % 10000//1000])

def loop():
    global counter
    currentState = 0
    lastState = 0
    while True:
        display()
        currentState=GPIO.input(sensorPin)
        if (currentState == 0) and (lastState == 1):
            counter +=1
        lastState=currentState

def setup():
    GPIO.setmode(GPIO.BCM)
    GPIO.setup(SDI, GPIO.OUT)
    GPIO.setup(RCLK, GPIO.OUT)
    GPIO.setup(SRCLK, GPIO.OUT)
    for i in placePin:
        GPIO.setup(i, GPIO.OUT)
    GPIO.setup(sensorPin, GPIO.IN)

def destroy():   # When "Ctrl+C" is pressed, the function is executed.
    GPIO.cleanup()

if __name__ == '__main__':  # Program starting from here
    setup()
    try:
        loop()
    except KeyboardInterrupt:
        destroy()

Code Explanation

Based on 1.1.5 4-Digit 7-Segment Display, this lesson adds PIR module to change the automatic counting of lesson 1.1.5 into count detecting. When the PIR detects that someone is passing by, the number on the 4-digit segment display will add 1.

def display():
    global counter
    clearDisplay()
    pickDigit(0)
    hc595_shift(number[counter % 10])

    clearDisplay()
    pickDigit(1)
    hc595_shift(number[counter % 100//10])

    clearDisplay()
    pickDigit(2)
    hc595_shift(number[counter % 1000//100])

    clearDisplay()
    pickDigit(3)
    hc595_shift(number[counter % 10000//1000])

First, start the fourth segment display, write the single-digit number. Then start the third segment display, and type in the tens digit; after that, start the second and the first segment display respectively, and write the hundreds and thousands digits respectively. Because the refreshing speed is very fast, we see a complete four-digit display.

def loop():
global counter
    currentState = 0
    lastState = 0
    while True:
        display()
        currentState=GPIO.input(sensorPin)
        if (currentState == 0) and (lastState == 1):
            counter +=1
        lastState=currentState

This is the main function: display the number on the 4-digit segment display and read the PIR value. When the PIR detects that someone is passing by, the number on the 4-digit segment display will add 1.

Phenomenon Picture

_images/image236.jpeg