7 segment display is a simple electronic display composed of 7 (surprise) LEDs. It is common to find an addictional led for a little dot near classic 7 segments. It runs in a very simple way with Raspberry PI GPIOs and Python coding
In this tutorial I’m going t show you how to connect and configure a 7 segment display with a Raspberry PI. If you are searching for “4 digit-7 segment display” guide, you may be interested in my 4 Digit diplay tutorial.
7 segment display is used within a wide number application, usually to single a display number. These devices have a simple internal wiring diagrams, which maps one by one LEDs to its pins:
In this article we’ll control a 7 Segment Display from a Raspberry PI Zero W. This article applies also to newer Raspberry PI computer boards.
What We Need
As usual, I suggest adding from now to your favourite e-commerce shopping cart all the needed hardware, so that at the end you will be able to evaluate overall costs and decide if continue with the project or remove them from the shopping cart. So, hardware will be only:
- Raspberry PI Zero W (including proper power supply or using a smartphone micro usb charger with at least 3A) or newer Raspberry PI Board
- high speed micro SD card (at least 16 GB, at least class 10)
- a 7 Segment Display
- Dupont wirings
- 8x resistors (220 Ohm used)
Many of listed hardware (except from Raspberry PI Zero W and micro SD Card) can be bought alone or can be also found in the useful Elegoo starter kit.
Check hardware prices with following links:
Prepare cabling according to following wiring diagram:
This wiring produces the following mapping between Display and Raspberry PI:
|Display Segment||Display Pin||Raspberry PI phisical pin||Raspberry PI BCM GPIO|
So, each Raspberry PI pin / GPIO powers on/off its related segment. Powering on appropriated segments together will display the number we want to show.
Please find below the overall picture:
Make your OS up-to-date. From the terminal, use the following commands:
sudo apt update sudo apt upgrade
RPI.GPIO should be already installed (otherwise, you can get it installed with the command “sudo apt install python3-rpi.gpio”).
Get 7 Segment Python Script
Get segDisplay.py script from my download area:
This script will be explained later in this post.
This script can be used by simply calling segDisplay.py with a simple argument passing the number to display and the dot (if required). So, for example:
python3 segDisplay.py 1.
Will display the number “1” and powers ON the dot led.
python3 segDisplay.py 5
Will display the number “5” and powers OFF the dot led.
python3 segDisplay.py 10
Will power OFF the whole display.
First section imports required libraries
import RPi.GPIO as GPIO
This script works mapping following pins activation according to wiring diagram:
Num_to Display -> GPIO pins state 0 -> [1,1,1,1,1,1,0] 1 -> [0,1,1,0,0,0,0] 2 -> [1,1,0,1,1,0,1] 3 -> [1,1,1,1,0,0,1] 4 -> [0,1,1,0,0,1,1] 5 -> [1,0,1,1,0,1,1] 6 -> [1,0,1,1,1,1,1] 7 -> [1,1,1,0,0,0,0] 8 -> [1,1,1,1,1,1,1] 9 -> [1,1,1,1,0,1,1] 10 (OFF) -> [0,0,0,0,0,0,0]
Dot GPIO (6) is managed alone. The last array is used to deactivate the Display.
GPIO id order is stored in a simple array. GPIO order is according to mapping. GPIOs are also all set as output.
display_list = [17,27,22,10,9,11,5] GPIO.setmode(GPIO.BCM) GPIO.setwarnings(False) for pin in display_list: GPIO.setup(pin,GPIO.OUT) # setting pins GPIO.setup(6,GPIO.OUT) # setting dot pin GPIO.setwarnings(True)
Warnings are disabled because this script will leave display active after execution.
A new array is defined, listing all possible combinations to Display. So, arrSeq stores GPIO status to show “0” on display. arrSeq will be managed alone to push a GPIO.cleanup.
arrSeg = [[1,1,1,1,1,1,0],\ # -> arrSeq displays 0 [0,1,1,0,0,0,0],\ # -> arrSeq displays 1 [1,1,0,1,1,0,1],\ # -> arrSeq displays 2 [1,1,1,1,0,0,1],\ # -> arrSeq displays 3 [0,1,1,0,0,1,1],\ # -> arrSeq displays 4 [1,0,1,1,0,1,1],\ # -> arrSeq displays 5 [1,0,1,1,1,1,1],\ # -> arrSeq displays 6 [1,1,1,0,0,0,0],\ # -> arrSeq displays 7 [1,1,1,1,1,1,1],\ # -> arrSeq displays 8 [1,1,1,1,0,1,1]] # -> arrSeq displays 9
Then a basic error check on the passed argument is performed. On error, program exits:
if len(sys.argv) > 2: print("ERROR: too many arguments") sys.exit() elif len(sys.argv) == 1: print("ERROR: missing argument") sys.exit() elif int(sys.argv.replace(".", "")) > 10 or int(sys.argv.replace(".", ""))<0: print("ERROR: insert a number between 0 and 10") sys.exit()
Dot led activation is managed alone, so the only number is passed to the main diplay procedure:
if sys.argv.count(".") == 1:GPIO.output(6,1) numDisplay = int(sys.argv.replace(".", ""))
The final operation is just activating GPIOs according to the number passed on the argument. This script then exits:
if numDisplay == 10: GPIO.cleanup() else: GPIO.output(display_list, arrSeg[numDisplay]) sys.exit()
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