https://fccid.io/R4WRCQR02
https://fccid.io/R4WRCQR02/Internal-Photos/Exhibit-C-Internal-Photographs-per-2-1033-b7-2908818.pdf

https://github.com/zerog2k/rcqr01

MCU: It uses a Nordic nRF51822 (Cortex-M0, 256 kB flash, 16 kB RAM)
LCD: A 360×160, 2‑bit grayscale ST7586 display, driven over SPI with 3×2-bit pixels per byte
Keyboard: An 8×8 matrix, QWERTY layout, with pinouts documented. Rows and columns are easily traced
Storage: A SPI EEPROM (CAT25512, 512 kbit) accessible via defined pins



https://docs.nordicsemi.com/bundle/sdk_nrf5_v9.0.0/page/group_mem_manager.html
https://docs.nordicsemi.com/bundle/sdk_nrf5_v12.3.0/page/sdk_for_custom_boards.html
https://docs.nordicsemi.com/bundle/sdk_nrf5_v12.3.0/page/lib_rtos.html
^ search "nordic nrf51 sdk 12.3.0" in https://docs.nordicsemi.com/


https://www.nordicsemi.com/Products/Development-hardware/nRF52-DK/GetStarted
development kit