Category Archives: Python

Library for Reading a 16 Button Keypad on the Raspberry Pi

October 27, 2022 admin

In this lesson we show you how to create a Python Class and Library that allows you to easily get user input on a Raspberry Pi from a 16 button keypad. This will allow very easy interaction with the keypad.

The Library Code which we develop in the video is presented below for your convenience:

class keypad:
    def __init__(self,rows=[11,13,15,29],columns=[31,33,35,37],keyLabels=[['1','2','3','A'],['4','5','6','B'],['7','8','9','C'],['*','0','#','D']],retChar='D'):
        import RPi.GPIO as GPIO
        self.rows=rows
        self.columns=columns
        self.retChar=retChar
        self.keyLabels=keyLabels
        GPIO.setmode(GPIO.BOARD)
        for i in rows:
            GPIO.setup(i,GPIO.OUT)
        for j in columns:
            GPIO.setup(j,GPIO.IN,pull_up_down=GPIO.PUD_DOWN)
    def readKeypad(self):
        from time import sleep
        import RPi.GPIO as GPIO
        keyStrokes=''
        noPress=True
        noPressOld=True
        while True:
            noPress=True
            for myRow in [0,1,2,3]:
                for myColumn in [0,1,2,3]:
                    GPIO.output(self.rows[myRow],GPIO.HIGH)
                    butVal=GPIO.input(self.columns[myColumn])
                    GPIO.output(self.rows[myRow],GPIO.LOW)
                    if butVal==1:
                        myChar=self.keyLabels[myRow][myColumn]
                        if myChar==self.retChar:
                            return keyStrokes
                        noPress=False
                    if butVal==1 and noPressOld==True and noPress==False:
                        keyStrokes=keyStrokes+myChar
            noPressOld=noPress
            sleep(.25)

class keypad:

def __init__(self,rows=[11,13,15,29],columns=[31,33,35,37],keyLabels=[['1','2','3','A'],['4','5','6','B'],['7','8','9','C'],['*','0','#','D']],retChar='D'):

import RPi.GPIO as GPIO

self.rows=rows

self.columns=columns

self.retChar=retChar

self.keyLabels=keyLabels

GPIO.setmode(GPIO.BOARD)

for i in rows:

GPIO.setup(i,GPIO.OUT)

for j in columns:

GPIO.setup(j,GPIO.IN,pull_up_down=GPIO.PUD_DOWN)

def readKeypad(self):

from time import sleep

import RPi.GPIO as GPIO

keyStrokes=''

noPress=True

noPressOld=True

while True:

noPress=True

for myRow in [0,1,2,3]:

for myColumn in [0,1,2,3]:

GPIO.output(self.rows[myRow],GPIO.HIGH)

butVal=GPIO.input(self.columns[myColumn])

GPIO.output(self.rows[myRow],GPIO.LOW)

if butVal==1:

myChar=self.keyLabels[myRow][myColumn]

if myChar==self.retChar:

return keyStrokes

noPress=False

if butVal==1 and noPressOld==True and noPress==False:

keyStrokes=keyStrokes+myChar

noPressOld=noPress

sleep(.25)

To use this code as a library, save it in the same folder as your python programs, and save it as KPLIB.py

import RPi.GPIO as GPIO
from KPLIB import keypad
myPad=keypad(retChar='A')
myString=myPad.readKeypad()
print(myString)
GPIO.cleanup()

import RPi.GPIO as GPIO

from KPLIB import keypad

myPad=keypad(retChar='A')

myString=myPad.readKeypad()

print(myString)

GPIO.cleanup()

This is a simple demo program that calls the library above, to receive input from the keypad.

Python, Raspberry Pi

Using a Photoresistor to Detect Light on the Raspberry Pi

September 29, 2022 admin

In this lesson we show how to detect light levels with a Raspberry Pi and a photoresistor. The photoresistor is connected in a voltage divider to the ADC0834 AD converter, which then connects to the Raspberry Pi. The schematic of the circuit is below:

This schematic shows how to connect a photoresistor to the Raspberry Pi

Python, Raspberry Pi

Library for I2C Connection of the LCD1602 to the Raspberry PI

August 31, 2022 admin

This lesson shows how to connect an LCD1602 to a Raspberry Pi using only 4 wires by I2C. You will need to copy the code below, and create a program called LCD1602.py, and save it in the same folder your main python programs are in.

#!/usr/bin/env python3

import time
import smbus2 as smbus

BUS = smbus.SMBus(1)

def write_word(addr, data):
    global BLEN
    temp = data
    if BLEN == 1:
        temp |= 0x08
    else:
        temp &= 0xF7
    BUS.write_byte(addr ,temp)

def send_command(comm):
    # Send bit7-4 firstly
    buf = comm & 0xF0
    buf |= 0x04               # RS = 0, RW = 0, EN = 1
    write_word(LCD_ADDR ,buf)
    time.sleep(0.002)
    buf &= 0xFB               # Make EN = 0
    write_word(LCD_ADDR ,buf)

    # Send bit3-0 secondly
    buf = (comm & 0x0F) << 4
    buf |= 0x04               # RS = 0, RW = 0, EN = 1
    write_word(LCD_ADDR ,buf)
    time.sleep(0.002)
    buf &= 0xFB               # Make EN = 0
    write_word(LCD_ADDR ,buf)

def send_data(data):
    # Send bit7-4 firstly
    buf = data & 0xF0
    buf |= 0x05               # RS = 1, RW = 0, EN = 1
    write_word(LCD_ADDR ,buf)
    time.sleep(0.002)
    buf &= 0xFB               # Make EN = 0
    write_word(LCD_ADDR ,buf)

    # Send bit3-0 secondly
    buf = (data & 0x0F) << 4
    buf |= 0x05               # RS = 1, RW = 0, EN = 1
    write_word(LCD_ADDR ,buf)
    time.sleep(0.002)
    buf &= 0xFB               # Make EN = 0
    write_word(LCD_ADDR ,buf)

def init(addr, bl):
#    global BUS
#    BUS = smbus.SMBus(1)
    global LCD_ADDR
    global BLEN
    LCD_ADDR = addr
    BLEN = bl
    try:
        send_command(0x33) # Must initialize to 8-line mode at first
        time.sleep(0.005)
        send_command(0x32) # Then initialize to 4-line mode
        time.sleep(0.005)
        send_command(0x28) # 2 Lines & 5*7 dots
        time.sleep(0.005)
        send_command(0x0C) # Enable display without cursor
        time.sleep(0.005)
        send_command(0x01) # Clear Screen
        BUS.write_byte(LCD_ADDR, 0x08)
    except:
        return False
    else:
        return True

def clear():
    send_command(0x01) # Clear Screen

def openlight():  # Enable the backlight
    BUS.write_byte(0x27,0x08)
    BUS.close()

def write(x, y, str):
    if x < 0:
        x = 0
    if x > 15:
        x = 15
    if y <0:
        y = 0
    if y > 1:
        y = 1

    # Move cursor
    addr = 0x80 + 0x40 * y + x
    send_command(addr)

    for chr in str:
        send_data(ord(chr))

if __name__ == '__main__':
    init(0x27, 1)
    write(4, 0, 'Hello')
    write(7, 1, 'world!')

100

101

#!/usr/bin/env python3

import time

import smbus2 as smbus

BUS = smbus.SMBus(1)

def write_word(addr, data):

global BLEN

temp = data

if BLEN == 1:

temp |= 0x08

else:

temp &= 0xF7

BUS.write_byte(addr ,temp)

def send_command(comm):

# Send bit7-4 firstly

buf = comm & 0xF0

buf |= 0x04 # RS = 0, RW = 0, EN = 1

write_word(LCD_ADDR ,buf)

time.sleep(0.002)

buf &= 0xFB # Make EN = 0

write_word(LCD_ADDR ,buf)

# Send bit3-0 secondly

buf = (comm & 0x0F) << 4

buf |= 0x04 # RS = 0, RW = 0, EN = 1

write_word(LCD_ADDR ,buf)

time.sleep(0.002)

buf &= 0xFB # Make EN = 0

write_word(LCD_ADDR ,buf)

def send_data(data):

# Send bit7-4 firstly

buf = data & 0xF0

buf |= 0x05 # RS = 1, RW = 0, EN = 1

write_word(LCD_ADDR ,buf)

time.sleep(0.002)

buf &= 0xFB # Make EN = 0

write_word(LCD_ADDR ,buf)

# Send bit3-0 secondly

buf = (data & 0x0F) << 4

buf |= 0x05 # RS = 1, RW = 0, EN = 1

write_word(LCD_ADDR ,buf)

time.sleep(0.002)

buf &= 0xFB # Make EN = 0

write_word(LCD_ADDR ,buf)

def init(addr, bl):

# global BUS

# BUS = smbus.SMBus(1)

global LCD_ADDR

global BLEN

LCD_ADDR = addr

BLEN = bl

try:

send_command(0x33) # Must initialize to 8-line mode at first

time.sleep(0.005)

send_command(0x32) # Then initialize to 4-line mode

time.sleep(0.005)

send_command(0x28) # 2 Lines & 5*7 dots

time.sleep(0.005)

send_command(0x0C) # Enable display without cursor

time.sleep(0.005)

send_command(0x01) # Clear Screen

BUS.write_byte(LCD_ADDR, 0x08)

except:

return False

else:

return True

def clear():

send_command(0x01) # Clear Screen

def openlight(): # Enable the backlight

BUS.write_byte(0x27,0x08)

BUS.close()

def write(x, y, str):

if x < 0:

x = 0

if x > 15:

x = 15

if y <0:

y = 0

if y > 1:

y = 1

# Move cursor

addr = 0x80 + 0x40 * y + x

send_command(addr)

for chr in str:

send_data(ord(chr))

if __name__ == '__main__':

init(0x27, 1)

write(4, 0, 'Hello')

write(7, 1, 'world!')

Arduino with Python, Python

Using an Arduino with Python LESSON 11: Controlling an LED from Python

March 22, 2022 admin

In this video lesson, we show how to control an LED using python. Python sends commands to arduino, which then controls the LED. We also create a vPython visual, where the ‘Virtual’ LED mimics the behavior of the real LED. This a really cool demonstration and hope you enjoy it. I include below the code we develop in the video. On the arduino side we end up with the following:

int redPin=11;
int greenPin=10;
int bluePin=9;
int redVal=255;
int greenVal=255;
int blueVal=255;
String cmd;
void setup() {
  // put your setup code here, to run once:
Serial.begin(115200);
pinMode(redPin,OUTPUT);
pinMode(greenPin,OUTPUT);
pinMode(bluePin,OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
  while(Serial.available()==0){
  }
redVal=Serial.readStringUntil(':').toInt();
greenVal=Serial.readStringUntil(':').toInt();
blueVal=Serial.readStringUntil('\r').toInt();

analogWrite(redPin,redVal);
analogWrite(greenPin,greenVal);
analogWrite(bluePin,blueVal);

}

int redPin=11;

int greenPin=10;

int bluePin=9;

int redVal=255;

int greenVal=255;

int blueVal=255;

String cmd;

void setup() {

// put your setup code here, to run once:

Serial.begin(115200);

pinMode(redPin,OUTPUT);

pinMode(greenPin,OUTPUT);

pinMode(bluePin,OUTPUT);

}

void loop() {

// put your main code here, to run repeatedly:

while(Serial.available()==0){

}

redVal=Serial.readStringUntil(':').toInt();

greenVal=Serial.readStringUntil(':').toInt();

blueVal=Serial.readStringUntil('\r').toInt();

analogWrite(redPin,redVal);

analogWrite(greenPin,greenVal);

analogWrite(bluePin,blueVal);

}

And on the python side we have:

import serial
from vpython import *

arduinoData=serial.Serial('com3',115200)

myOrb=sphere(color=color.black,radius=1)

while True:
    myCmd=input('Please Input Your Color R:G:B 0-255 ')
    myCmd=myCmd+'\r'
    arduinoData.write(myCmd.encode())
    myColor=myCmd.split(':')
    red=int(myColor[0])
    green=int(myColor[1])
    blue=int(myColor[2])
    myOrb.color=vector(red/255,green/255,blue/255)

import serial

from vpython import *

arduinoData=serial.Serial('com3',115200)

myOrb=sphere(color=color.black,radius=1)

while True:

myCmd=input('Please Input Your Color R:G:B 0-255 ')

myCmd=myCmd+'\r'

arduinoData.write(myCmd.encode())

myColor=myCmd.split(':')

red=int(myColor[0])

green=int(myColor[1])

blue=int(myColor[2])

myOrb.color=vector(red/255,green/255,blue/255)

3D Graphics with Visual Python, Arduino, Arduino with Python, Python

Using an Arduino with Python LESSON 8: Live Thermometer 3D Visual Using DHT11

March 1, 2022 admin

In this video lesson we connect the Arduino to a DHT11 temperature and humidity sensor. We show how to wire the device up, and then how to code the Arduino. The data is passed from the Arduino to python. We then create a live 3D thermometer model that updates as the temperature changes.

On the arduino side, this is the code which we use:

#include "DHT.h"
#define DHTPIN 2
#define DHTTYPE DHT11

float tempF;
float tempC;
float humidity;

int setTime=500;
int dt=1000;

DHT TH(DHTPIN,DHTTYPE);

void setup() {
  // put your setup code here, to run once:
Serial.begin(115200);
TH.begin();
delay(setTime);
}
void loop() {
  // put your main code here, to run repeatedly:
tempC=TH.readTemperature();
tempF=TH.readTemperature(true);
humidity=TH.readHumidity();


Serial.print(tempF);
Serial.print(",");
Serial.println(humidity);

delay(dt);
}

#include "DHT.h"

#define DHTPIN 2

#define DHTTYPE DHT11

float tempF;

float tempC;

float humidity;

int setTime=500;

int dt=1000;

DHT TH(DHTPIN,DHTTYPE);

void setup() {

// put your setup code here, to run once:

Serial.begin(115200);

TH.begin();

delay(setTime);

}

void loop() {

// put your main code here, to run repeatedly:

tempC=TH.readTemperature();

tempF=TH.readTemperature(true);

humidity=TH.readHumidity();

Serial.print(tempF);

Serial.print(",");

Serial.println(humidity);

delay(dt);

}

Then on the python side, we use the following code:

import time
import serial
from vpython import *

arduinoData=serial.Serial('com3',115200)
time.sleep(.5)
digValue=label(text='50',height=20,box=False,pos=vector(0,-2.5,2))
bulb=sphere(radius=1,color=color.red,pos=vector(0,-3,0))
cyl=cylinder(radius=.6,color=color.red,axis=vector(0,1,0),length=6,pos=vector(0,-3,0))
bulbGlass=sphere(radius=1.2,color=color.white,opacity=.25,pos=vector(0,-3,0))
cylGlass=cylinder(radius=.8,color=color.white,axis=vector(0,1,0),opacity=.25,length=6,pos=vector(0,-3,0))
for temp in range(0,115,10):
    tickPos=4.5/115*temp+1.5
    tick=cylinder(radius=.7,color=color.black,length=.1,axis=vector(0,1,0),pos=vector(0,tickPos-3,0))
    label=text(text=str(temp),color=color.white,pos=vector(-2,tickPos-3,0),height=.3)
while True:
    while arduinoData.in_waiting==0:
        pass
    dataPacket=arduinoData.readline()
    dataPacket=str(dataPacket,'utf-8')
    dataPacket=dataPacket.strip('\r\n')
    dataPacket=dataPacket.split(',')
    temp=float(dataPacket[0])
    hum=float(dataPacket[1])
    len=(4.5/115)*temp+1.5
    cyl.length=len
    digValue.text=str(temp)

import time

import serial

from vpython import *

arduinoData=serial.Serial('com3',115200)

time.sleep(.5)

digValue=label(text='50',height=20,box=False,pos=vector(0,-2.5,2))

bulb=sphere(radius=1,color=color.red,pos=vector(0,-3,0))

cyl=cylinder(radius=.6,color=color.red,axis=vector(0,1,0),length=6,pos=vector(0,-3,0))

bulbGlass=sphere(radius=1.2,color=color.white,opacity=.25,pos=vector(0,-3,0))

cylGlass=cylinder(radius=.8,color=color.white,axis=vector(0,1,0),opacity=.25,length=6,pos=vector(0,-3,0))

for temp in range(0,115,10):

tickPos=4.5/115*temp+1.5

tick=cylinder(radius=.7,color=color.black,length=.1,axis=vector(0,1,0),pos=vector(0,tickPos-3,0))

label=text(text=str(temp),color=color.white,pos=vector(-2,tickPos-3,0),height=.3)

while True:

while arduinoData.in_waiting==0:

pass

dataPacket=arduinoData.readline()

dataPacket=str(dataPacket,'utf-8')

dataPacket=dataPacket.strip('\r\n')

dataPacket=dataPacket.split(',')

temp=float(dataPacket[0])

hum=float(dataPacket[1])

len=(4.5/115)*temp+1.5

cyl.length=len

digValue.text=str(temp)

Technology Tutorials

Category Archives: Python

Library for Reading a 16 Button Keypad on the Raspberry Pi

Using a Photoresistor to Detect Light on the Raspberry Pi

Library for I2C Connection of the LCD1602 to the Raspberry PI

Using an Arduino with Python LESSON 11: Controlling an LED from Python

Using an Arduino with Python LESSON 8: Live Thermometer 3D Visual Using DHT11

Making The World a Better Place One High Tech Project at a Time. Enjoy!