Small project #1 — 8bit breadboard port status indicator


A real quicky!

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After having written an Arduino library [1],[2] for the Macroblock MBI5030 16ch PWM LED driver, I was in dire need for a lot of LEDs for testing. Of course one doesn’t want to deal with millions of wires, when all you want to do is test / debug your code. It just gets too messy. So I built a test-jig with through-hole components, but that left a few things to be desired: it only worked in common-anode configuration, it was too large, assembly sucked.

So I fired up KiCad and not much later this little thing was born and the files sent off to be fabricated. Except for a tolerance issue with the drill holes, it works as expected. The latest revision has the ‘the headers won’t fit!’ issue resolved. Just in case you download the files.

Now I can just plug this board into a breadboard and start debugging code. If wired up in the right way, one only needs one additional wire to supply power. The other pins should be right next to the LED driver’s outputs.

Why two rows of LEDs you ask? Simple! The common pin can be either + or GND. In the first case the LED pins must go to GND to get light, in the 2nd case they must go to the supply voltage. The LEDs are wired up in such a way that either the top or the bottom row lights up.


It costs a bit more in parts, but the great advantage is an almost complete absence of the need to rewire the whole thing for different LED driver types. The one common pin / wire doesn’t count!


A couple of images of the latest version:




Assembly in 3 steps:

1) LEDs first!




2) Resistor arrays next


3) Finalize with pin header


Use plenty of flux – unless you’re a masochist.

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2 Responses to Small project #1 — 8bit breadboard port status indicator

  1. Matthew Cook says:


    I just wanted to say that this solution has helped me out so much! I am using it right now on my breadboard to monitor the first 8 address pins on a Z80 Microprocessor which happen to mine up perfectly with the ground of the board. What a great design!

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