====== nRF52840 Notes ======

===== High Voltage Mode =====

==== Motivation ====

  * Simplify BoM and layout by using the nrf52840 VDDH -> VDD LDO instead of an external 3.3 V LDO

==== Limitations ====

  * <25 mA output from VDDH to VDD (REG0)
  * 2.5 V < VDDH < 5.5 V

==== Requirements ====

  * VDD must not be connected to VDDH or any power supply at reset
  * Adafruit nRF52 Bootloader -> board.h -> ''#define UICR_REGOUT0_VALUE UICR_REGOUT0_VOUT_3V3'' ([[https://github.com/search?q=repo%3Aadafruit%2FAdafruit_nRF52_Bootloader+%22%23define+UICR_REGOUT0_VALUE+UICR_REGOUT0_VOUT_3V3%22&type=code|Adafruit nRF52 Bootloader GitHub search]])
    *  If not defined, default REGOUT0 output = VDD = 1.8 V and GPIO output high = VDD = 1.8 V

==== Notes ====

  * ''nice_nano'' seems like a good bootloader variant to use if you need High Voltage mode

==== Further Reading ====

  * [[https://docs.nordicsemi.com/bundle/ps_nrf52840/page/power.html|nrf52840 — POWER — Power supply]]

===== NFC Pins as GPIO =====

==== Motivation ====

  * Have more usable GPIO pins

==== Requirements ====

  * Adafruit nRF52 Bootloader -> board.mk -> ''USE_NFCT'' must not be ''= yes'' ([[https://github.com/search?q=repo%3Aadafruit%2FAdafruit_nRF52_Bootloader+%22USE_NFCT%22&type=code|Adafruit nRF52 Bootloader GitHub search]])


===== Flash Bootloader with ST-Link =====

  * ''%%openocd -f interface/stlink.cfg -f target/nrf52.cfg -c "program nice_nano_bootloader-0.9.2_s140_6.1.1.hex verify reset exit"%%''