A few months back I wrote an article on the “Yellow Development Board” from Ai-Thinker. At the time it was, I admit, an attempt to add a little balance to the blog after my lambasting of their “Black Board T5”. However, after a few months of using these little beasties, I suddenly realized that it had become my go-to board for new, ESP8266-based projects. My experience with electronics dates back way beyond transistors, let alone integrated circuits or microcontrollers, so one of the tools I still have in my kit is a wire-wrap pen, which turned out to be quite handy with the “Yellow Development Board” (and that is way too much of a mouthful, so from here onwards I’ll refer to it simply as “Yellow”).
Wire-wrapping is just what it sounds like… it was a technique used extensively in the early days of computer manufacturing to provide interconnects between components. Typically, individual chips would be plugged into ic-sockets with long, chunky pins with a square profile. Wire-wrap wire is single core, so the “pen” enabled you to strip the insulation off the end of your wire and then wrap it tightly around the pin (the square profile ensuring that the electrical connection was good, as the corners bit into the wire).
I mention this not because of a sudden burst of nostalgia, but because the header pins on the Yellow board reminded me of wire-wrap as soon as I saw them and one of the really good things about wire wrap (and there were plenty of bad things, as anyone who had to troubleshoot a wire-wrapped system will tell you) is that it was, and still is, one of the fastest ways to prototype a new circuit. You don’t have to wait for a soldering iron to heat up and you don’t lose half of your connections if you accidentally knock your breadboard onto the floor. So wire-wrapping seemed like a natural step for quickly connecting up the Yellow board to some peripherals when building a project. The header pins are not ideal (they’re a little too skinny and definitely not long enough), but they’re more than good enough for prototyping. It was only a few minutes work to connect up a DS3231 i2c RTC board (+ve, gnd, clock and data) and only another couple of minutes to add yet another board (this time a custom i2c slave built from a PIC16F1825) for more fun and experimentation (I should add that the RTC was something which I already knew was working and was just a test connection to ensure that i2c still worked with the red LEDs on the Yellow board’s i2c lines still in place; the PIC board was/is the intended target for that particular project).
The point here is that it proved to be incredibly easy to integrate an ESP8266 into a project using the Yellow board. It even had the added advantages of having LEDs on virtually all of the available pins, so there was some visual debug capability thrown in for free.
Shortly after this initial foray into i2c, I came across Cicero’s Ethernet-for-the-ESP8266 project and wrote up an entry here on the process of connecting the Yellow board to an ENC28J60 ethernet module to enable hard-wired ethernet to the ESP (on a side note, keep an eye open for an update from Cicero for a Linux-specific version of this project, coming soon).
So, over the months the awkwardly named “Yellow Development Board” has earned a place in my ESP8266 arsenal as a versatile and well-equipped prototyping tool and in the next post, I’ll look in a little more detail at a doorbell/dash type button project and how it interfaces with MQTT.
[Where to get these boards …I don’t generally give links to specific merchants, but the “Yellow” doesn’t seem to be quite so universally available as it once was. When I was searching for a new supplier earlier I came across this eBay store selling them at a very good price. The store has a feedback rating of 99.8% on over 20,000 sales, so they must be doing something right, but I should emphasize that, although I have ordered from them today, I haven’t ever used them before, so this is a “find”, but in no way an endorsement.]