Skip to main content

Raspberry Pi: Building an LED Digital Clock

As I mentioned in a previous post, I really enjoyed reading Programming Raspberry Pi: Getting Started with Python. One of the chapters in the book teaches you how to build an LED digital clock. It took some futzing around, but I finally got it done :)

The first problem I had was that I didn't know how to solder. My buddy Chris Dudte gave me a kit to learn. I watched a bunch of YouTube videos with the kids in my Raspberry Pi class, and then we put the circuit board together. Problem solved.

The next two problems I encountered were with the author's library for talking to the smbus for controlling the LEDs, i2c7segment. One of the problems resulted in my saying quite a few less than charitable words under my breath. The Python code kept giving me the error message "IOError: [Errno 5] Input/output error".

I finally figured it out. On line 42 of i2c7segment.py, the code is hardcoded to use smbus.SMBus(0). However, sometimes you need to use smbus.SMBus(1). You can run "sudo i2cdetect -y 0" and "sudo i2cdetect -y 1" to figure out which bus to use. You should see "70" in one of these two. The hardest part of figuring out this problem was that I thought the software must be correct, and that I must have wired it or soldered it wrong. My guess is that this might be a Raspberry Pi model A vs. model B thing.

To hack around the problem, I edited i2c7segment.py to use bus number 1. A better approach would be to allow the calling code to pass a bus number or to try to autoselect it; however, I didn't bother.

Anyway, I'm super excited that I got the project done, especially considering this is the first time I've ever done something like this. Special thanks to my buddy Chris Dudte for all his support and for giving me a Raspberry Pi in the first place!

Comments

Sam Rushing said…
Congrats, nice job!

I've been thinking for a while about building a 'digital pendulum' clock. A silly thing, really: it would consist of an electromagnetic escapement controlled by something like a Pi. Of course, the clock on board the Pi would be orders of magnitude more accurate; but I like the idea of a meter-long pendulum and an LED display, nothing else.
jjinux said…
That'd be neat!
Mehmet said…
Really good toy to show how programming and the digital world works. I used a lcd display to show my son this but later I saw it was a bit hard, an led display like this would be much easier. Great :)! 

Popular posts from this blog

Drawing Sierpinski's Triangle in Minecraft Using Python

In his keynote at PyCon, Eben Upton, the Executive Director of the Rasberry Pi Foundation, mentioned that not only has Minecraft been ported to the Rasberry Pi, but you can even control it with Python . Since four of my kids are avid Minecraft fans, I figured this might be a good time to teach them to program using Python. So I started yesterday with the goal of programming something cool for Minecraft and then showing it off at the San Francisco Python Meetup in the evening. The first problem that I faced was that I didn't have a Rasberry Pi. You can't hack Minecraft by just installing the Minecraft client. Speaking of which, I didn't have the Minecraft client installed either ;) My kids always play it on their Nexus 7s. I found an open source Minecraft server called Bukkit that "provides the means to extend the popular Minecraft multiplayer server." Then I found a plugin called RaspberryJuice that implements a subset of the Minecraft Pi modding API for B

Ubuntu 20.04 on a 2015 15" MacBook Pro

I decided to give Ubuntu 20.04 a try on my 2015 15" MacBook Pro. I didn't actually install it; I just live booted from a USB thumb drive which was enough to try out everything I wanted. In summary, it's not perfect, and issues with my camera would prevent me from switching, but given the right hardware, I think it's a really viable option. The first thing I wanted to try was what would happen if I plugged in a non-HiDPI screen given that my laptop has a HiDPI screen. Without sub-pixel scaling, whatever scale rate I picked for one screen would apply to the other. However, once I turned on sub-pixel scaling, I was able to pick different scale rates for the internal and external displays. That looked ok. I tried plugging in and unplugging multiple times, and it didn't crash. I doubt it'd work with my Thunderbolt display at work, but it worked fine for my HDMI displays at home. I even plugged it into my TV, and it stuck to the 100% scaling I picked for the othe

Creating Windows 10 Boot Media for a Lenovo Thinkpad T410 Using Only a Mac and a Linux Machine

TL;DR: Giovanni and I struggled trying to get Windows 10 installed on the Lenovo Thinkpad T410. We struggled a lot trying to create the installation media because we only had a Mac and a Linux machine to work with. Everytime we tried to boot the USB thumb drive, it just showed us a blinking cursor. At the end, we finally realized that Windows 10 wasn't supported on this laptop :-/ I've heard that it took Thomas Edison 100 tries to figure out the right material to use as a lightbulb filament. Well, I'm no Thomas Edison, but I thought it might be noteworthy to document our attempts at getting it to boot off a USB thumb drive: Download the ISO. Attempt 1: Use Etcher. Etcher says it doesn't work for Windows. Attempt 2: Use Boot Camp Assistant. It doesn't have that feature anymore. Attempt 3: Use Disk Utility on a Mac. Erase a USB thumb drive: Format: ExFAT Scheme: GUID Partition Map Mount the ISO. Copy everything from