RP2040 test board, breadboard friedly.
Features:
-Li ion power optin (protection built in) auto switching power in case of usb unpluging
-RTC with separate 20mm cell
-microSD card slot
-all pins exposed (that are not used internaly for a dedicated task)
-both LDO and buck switching convertor for power, one of them may be used based on the SPDT switch
(later maybe just one of them may be populated and the switch replaced by a solder bridge)
-same pinout as rpi pico just wider form factor
-all pins labeled
-It requires a few extra wires to work since this is a 2 layer design and this was a scarifice
made in order to keep a solid ground plane under the entire PCB
Images: https://imgur.com/a/X6zGeTy