Tag Archives: Raspberry Pi

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:

Raspberry Pi

Creating a programmable Temperature Alarm with the Raspberry Pi

September 22, 2022 admin

In this video lesson we show how to create a programmable temperature alarm using the Raspberry Pi, the DHT11 sensor, the ADC0834, a potentiometer and a buzzer. The results are displayed on a LCD1602 LCD display with a i2c connection. The device operates in either program mode or monitor mode. Pressing the button puts you in programming mode. In this mode you turn the potentiometer until your desired set temperature is reached. Then pressing the button again will switch you to monitor mode. In monitor mode the current temperature and humidity are displayed on the LCD. When the temperature exceeds your setpoint, the buzzer will release an audible alarm. Below is the schematic for our build.

temperature sensor — This schematic shows how to create a programmable temperature alarm

Jetson Nano

AI on the Jetson Nano LESSON 62: Create a Streaming IP Camera from a Raspberry Pi Zero W

October 3, 2020 admin

In this lesson we learn to make a streaming IP camera with a Raspberry Pi Zero W, and Raspberry Pi camera. The Pi will create a RTP stream, which can then be read by a Jetson Nano on the same network. We use OpenCV to read the frames on the NVIDIA Jetson Nano side.

This is the command to launch the Raspberry Pi camera, and start the RTP stream. This command works well for the Raspberry Pi Camera, version 1.

raspivid -t 0 -w 1296 -h 730 -fps 30 -b 2000000 -awb auto -n  -o - | gst-launch-1.0 -v fdsrc ! h264parse ! rtph264pay config-interval=1 pt=96 ! gdppay ! tcpserversink host=0.0.0.0 port=8554

1	raspivid -t 0 -w 1296 -h 730 -fps 30 -b 2000000 -awb auto -n -o - \| gst-launch-1.0 -v fdsrc ! h264parse ! rtph264pay config-interval=1 pt=96 ! gdppay ! tcpserversink host=0.0.0.0 port=8554

For the Version 2 Camera, I recommend:

raspivid -t 0 -w 1280 -h 720 -fps 30 -b 2000000 -awb auto -n -o - | gst-launch-1.0 -v fdsrc ! h264parse ! rtph264pay config-interval=1 pt=96 ! gdppay ! tcpserversink host=0.0.0.0 port=8554

1	raspivid -t 0 -w 1280 -h 720 -fps 30 -b 2000000 -awb auto -n -o - \| gst-launch-1.0 -v fdsrc ! h264parse ! rtph264pay config-interval=1 pt=96 ! gdppay ! tcpserversink host=0.0.0.0 port=8554

This is the Gstreamer code on the Jetson Nano side to grab the RTP Frames. On host= below, be sure to use the IP address of your Raspberry Pi.

camSet2=' tcpclientsrc host=10.1.37.28 port=8554 ! gdpdepay ! rtph264depay ! h264parse ! nvv4l2decoder  ! nvvidconv flip-method='+str(flip)+' ! video/x-raw,format=BGRx ! videoconvert ! video/x-raw, width='+str(dispW)+', height='+str(dispH)+',format=BGR ! appsink  drop=true sync=false '

1	camSet2=' tcpclientsrc host=10.1.37.28 port=8554 ! gdpdepay ! rtph264depay ! h264parse ! nvv4l2decoder ! nvvidconv flip-method='+str(flip)+' ! video/x-raw,format=BGRx ! videoconvert ! video/x-raw, width='+str(dispW)+', height='+str(dispH)+',format=BGR ! appsink drop=true sync=false '

Raspberry Pi, Review

Comparison of Raspberry Pi Zero Model W and Onion Omega 2+

March 1, 2017 admin

There is a lot happening in the Maker Space! We have just watched two new major releases of embedded microprocessor platforms . . . the Raspberry Pi Zero Model W and the Onion Omega 2+. Both these platforms are impressive in that they both offer a small package with onboard WiFi for $10. This combination of features, price and size opens up a new world of possibilities for compact, portable projects.

After reviewing both of these platforms, we choose the Raspberry Pi Zero model W as the platform we will be pursuing at this point. The video above gives a head to head comparison of the two platforms, and the rational behind our decision.

Technology Tutorials

Tag Archives: Raspberry Pi

Library for Reading a 16 Button Keypad on the Raspberry Pi

Using a Photoresistor to Detect Light on the Raspberry Pi

Creating a programmable Temperature Alarm with the Raspberry Pi

AI on the Jetson Nano LESSON 62: Create a Streaming IP Camera from a Raspberry Pi Zero W

Comparison of Raspberry Pi Zero Model W and Onion Omega 2+

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