DIY $3 Single Chip Macro Keypad From Scratch

I receive a few DM mentioning that they want a budget numpad based on the CH552G. I am like: Why you need a numpad?

After chating with one of the person who send me a DM, I notice many mechanical keyboard users don't actually have a full sized keyboard. Instead, they would go with a keyboard without numpad, then buy an additional numpad and only took it out when they needs a numpad.

However, consider the CH552G. In this project, I am using

• 2 GPIO for LEDs
• 4 GPIO for key switches
• 3 GPIO for RGB
• 1 GPIO for mode toggle

So in total there are only 10 GPIO I can use. Is this even possible for me to build a fully functional numpad?

Maybe Yes, However

In theory you can use a grid layout to multiplex the number of switches by scanning them line by line. However, conversion design will takes in one diode per switch, which is really expensive in term of soldering jobs. I gonna need to find a way to make it under $5 if I am gonna make one myself :D

Anyway, if you really want a $5 numpad keyboard, feel free to let me know!

Recently my friend who went through a head surgery and ask me for one of this macro-keypad. I am like: Sure, it is so cheap and you seems in a terrible mood, you can have one for free.

So I gave him one. And the next day he told me that he is using his laptop with this keypad so he could be streaming songs and music, control playback from his own server just using 4 fingers, while lying in his hospital bed.

I am like: Dude, how smart is it you use it this way!

He also told me he is using this to skip through his anime collection so he could finish the whole 2 seasons of Yuru Camp during his hospital stay. What a cool assistive tech this could be :D