A breakout board and simple GPIO monitor for hardware debugging, for Wemos D1 mini and others

How many times have you wondered why a connected device doesn't do what it should, only to find you connected the wrong pin?
The breakout board sits between your project board and the micro-controller and monitors the ports in real time and under actual working conditions.
The breakout board layout shown here is for a Wemos D1-mini, but can be altered for other boards that have different spacings and number of pins.
You can check any pin for a high or a low logic level. There are 5 LEDs for high and 5 for low logic levels. In practice I have only ever needed one or two at any one time.
A simple example is to use it on the RX and TX pins of the serial port.
It's also interesting watching which pins get 'wiggled' at first boot, as this will make you wary of connecting certain peripherals.

[@DavidMulligan]

The answer to your question is many times. Especially when using device libraries for the first time, I have discovered that the pins are configured differently than I thought or not at all. I have used a cheap usb logic analyzer to solve this problem, but a breakout board like this seems easier.
This design change made led me think to think that it should be easy to wire up bi-color LEDs to show logic high or low for each input. Even better would be to have LEDs which show logic high, low or high-z for each output.

[@richardlangner]

If you use a bi-color LED there will always be light and you will miss the short pulses, as demonstrated by the green HIGH level LED in the video .
My design connects each LED via its resistor to either 3.3v or ground. When you connect both HIGH and LOW LEDs to one pin the LEDs are effectively in series across the supply, so a tri-state pin will cause both LEDs to glow. Be aware that the LEDs must have the same operating current for this to happen. My design uses red and green which have different operating currents, so in my case only the red glows (and dimly). Thanks for asking the question - you've prompted me to use identical LEDs in my next version.

[@hullinstruments]

Your videos are super and well organized. Would love some long-form videos from you if you ever fancy doing something like that

[@richardlangner]

Thanks for the comments. I like to keep the videos short and straight to the point. For a longer video, what did you have in mind?