While I enjoy the DIY thing, building a business requires a different mindset. I don’t want to cut out the creativity, but I also can’t afford to waste time. You’ll hear business types discuss the …

It’s been a fairly unfocused week, but I’ve somehow managed to allocate an hour here or there to letterbox. My goal has been to validate my current design choices: the use of shift registers to drive the display, fed by an …

As I was working on the preliminary letterbox design, I noticed a fairly severe oversight. All of my experiments were based on a single display module, which an ESP8266 or ESP32 can handle easily using our chosen algorithm.

The common i2c bus (or TWI, or whatever non-trademarked name your manufacturer is using) is fairly easy to design with. It’s just a couple of wires, right? Well, mostly… You also need a pair of pull-up resistors.

Early experiments are complete; it’s time to put together the list of what I want in my new toy. This is… surprisingly complicated. There are a lot of moving parts, so to speak, and many rabbit holes to go tripping …

We all know the ESP8266 and its more recent sibling the ESP32. They’re used in just about everything under the sun, both hobbyist and commercial. Mostly this is because they’re cheap, but also because they’re …

Today has been a non-hardware day, estimating the energy usage of the display under the various algorithms. I simply wrote a program to run the math, and found that my answers from yesterday were correct enough to be going on …

Sometimes you sit down to work and realize that you should have stopped earlier the previous day. This was an example of one such day. I didn’t really notice it until I looked at the pulse trains in the images I published, but the …

Display power consumption is going to be a problem for the LetterBox. Today’s project is to tinker with one of my newly-acquired displays and see what exactly I can get away with in terms of consumption. This will inform the rest …

Shortly after I revamped the site, I realized that I had a problem. There’s a nice feedback mechanism, but no way to tell if anyone uses it unless I go and look. It’s far too easy to miss incoming feedback. Sure, I could just make …

I just can’t resist tinkering. I’ve pushed out a change that does the following: Kills off an infinite loop bug that occurred if RabbitMQ lost the connection. Enables scrolling long messages.

I’ve long held a certain fascination with old-technology displays. There’s just something special about them. Notable on the list is the 14-segment alphanumeric variety. These displays are very similar to the ubiquitous 7-segment …