Cool! Though CH58/9x series might be better for efficiency because it's Bluetooth 5. CH57x is BT 4.
And QMK has already been ported to CH582 but personally haven't tried it yet. https://github.com/O-H-M2/qmk_port_ch582
Go for it! I have a schematic in mind but too lazy to learn KiCad. Would love to help out :)
Also, there's a commercially available CH552T dev board for about a dollar. I actually use this for development: https://www.aliexpress.com/item/1005004141926425.html
Even cheaper if you buy just the chip. Just add a USB connector and two capacitors then that's it. No crystal, flash, etc. needed. A CH552G goes for about 30 cents: https://www.aliexpress.com/item/1005003402478164.html
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