m5stack CardKB2 Keyboard Unit (ESP32-C61)

AI context

Dense context for pasting into a model prompt — addresses, pinout, voltages, tolerances and the vendor's reference circuit.

PART: M5Stack CardKB2 Keyboard Unit, SKU U215, an 84.7 x 54.3 x 1.0 mm (22.4 g) 42-key keyboard built on an ESP32-C61HF4 (RISC-V 32-bit single core at 120 MHz, 4 MB flash, 2.4 GHz Wi-Fi 6). The title carries the SoC, so part is null and the data sheet is Espressif's ESP32-C61 document.\nADDRESSES: none. The keyboard is not an I2C device; its expansion port carries a UART or GPIO pair, not a bus address.\nPINOUT: one HY2.0-4P socket, PORT.CUSTOM: pad 1 GND (Black), pad 2 5V (Red), pad 3 SDA / UART_RX / G26 (Yellow), pad 4 SCL / UART_TX / G25 (White). The vendor prints no pad numbers on the connector; the 1-4 order above is its own colour column. Two buttons are on the board itself - one Reset and one Boot - and both are separate from the 42 keys.\nSUPPLY: 5 V on pad 2 or over USB Type-C; published standby draw is 5 V at 19.31 mA. There is no on-board battery and no charging circuit.\nLOGIC: 3.3 V - the SoC's UART and GPIO are 3.3 V and the vendor publishes no 5 V tolerance for pads 3 and 4, so an external 5 V host needs level shifting on TX/RX.\nCIRCUIT: the vendor publishes no schematic for this SKU, so there are no pull-up, decoupling or ferrite values to record - nothing here is copied from a sibling board. The USB Type-C port is the power and flashing path, and the default firmware logs at 115200 bps 8N1.\nTRAPS: (1) Pads 3 and 4 are dual-function - G26/G25 as plain GPIO, or a UART whose default direction is not stated, so the firmware decides whether pad 3 is RX or SDA. (2) The port is called PORT.CUSTOM rather than PORT.A, so M5Stack's Unit library does not auto-detect a Unit plugged into it. (3) The 1.0 mm thickness is the PCB; the keycaps stand above it.