this post was submitted on 18 Mar 2026
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Programming
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Oh, that's cool. I hadn't heard of slimevr before.
My use case for the diode ROM board is to take 4 binary input bits (16 possible combinations) and translate them into what segments of a 7-segment LED display should be lit or unlit, in order to display the corresponding hexadecimal digit (0-9, A-F). Like so:
It could be used for any other case where you need to convert a 4-bit input into 16 possible 8-bit outputs. In theory you could use them in multiples for more address space, but I forgot to include an enable pin on the board to allow for that. Something to add to the next version.
Maybe I'm not very experienced. Why would someone need a device to translate a 4-bit input to an 8-bit output, is it not just 0110 -> 0000 0110?
Ah, sorry, I could have been more clear there. It can do arbitrary mappings between input values and output values. So for each possible 4-bit value, you can pick a different 8-bit value to be output.
For my case, I'm working with a 7-segment LED display, like the display on a microwave. It's got 7 LEDs arranged to display a number, plus an 8th LED for a decimal point. Like this:
.
if the ROM is getting 0000 for its input, it should light up all segments of the 7-segment display except for the horizontal one in the center, to display a zero. Then for the 0001 input, it should light up the two vertical segments on the right, leaving the rest dark, to display a one. And so on. Each output bit goes to a particular segment of the display.
To relate it more directly to programming, it's like having a 16 byte array. The input gives the array index that you want to access, and the output gives whatever byte is at that index.