A modified version of the Adafruit Feather nRF52840 bootloader board file found here:https://github.com/adafruit/Adafruit_nRF52_Bootloader/blob/master/src/boards/feather_nrf52840_express/board.h

feather_nrf52840_express.h

/**************************************************************************/
/*!
    @file     feather_nrf52840_express.h
    @author   hathach

    @section LICENSE

    Software License Agreement (BSD License)

    Copyright (c) 2018, Adafruit Industries (adafruit.com)
    All rights reserved.

    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions are met:
    1. Redistributions of source code must retain the above copyright
    notice, this list of conditions and the following disclaimer.
    2. Redistributions in binary form must reproduce the above copyright
    notice, this list of conditions and the following disclaimer in the
    documentation and/or other materials provided with the distribution.
    3. Neither the name of the copyright holders nor the
    names of its contributors may be used to endorse or promote products
    derived from this software without specific prior written permission.

    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS ''AS IS'' AND ANY
    EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
    WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
    DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE FOR ANY
    DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
    (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
    LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
    ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
    (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
    SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/**************************************************************************/

#ifndef _FEATHER52840_H
#define _FEATHER52840_H

#define _PINNUM(port, pin)    ((port)*32 + (pin))

/*------------------------------------------------------------------*/
/* LED
 *------------------------------------------------------------------*/
#define LEDS_NUMBER           2
#define LED_PRIMARY_PIN       _PINNUM(1, 15)
#define LED_SECONDARY_PIN     _PINNUM(1, 10)
#define LED_NEOPIXEL          16
#define BOARD_RGB_BRIGHTNESS  0x040404
#define LED_STATE_ON          1

#define LEDS_ACTIVE_STATE     LED_STATE_ON
#define LED_1 LED_PRIMARY_PIN
#define LED_2 LED_NEOPIXEL

#define LEDS_LIST { LED_1, LED_2 }

/*------------------------------------------------------------------*/
/* BUTTON
 *------------------------------------------------------------------*/
#define BUTTONS_NUMBER        2
#define BUTTON_1              _PINNUM(0, 15)
#define BUTTON_2              _PINNUM(0, 19)
#define BUTTON_PULL           NRF_GPIO_PIN_PULLUP

#define BUTTONS_ACTIVE_STATE 1

#define BUTTONS_LIST { BUTTON_1, BUTTON_2 }

/*------------------------------------------------------------------*/
/* UART
 *------------------------------------------------------------------*/
#define RX_PIN_NUMBER         8
#define TX_PIN_NUMBER         6
#define CTS_PIN_NUMBER        0
#define RTS_PIN_NUMBER        0
#define HWFC                  false

// Used as model string in OTA mode
#define DIS_MANUFACTURER      "Adafruit Industries"
#define DIS_MODEL             "Bluefruit Feather nRF52840 Express"

#define PRODUCT_NAME          "Adafruit Feather nRF52840 Express"
#define VOLUME_LABEL          "FTHR840BOOT"

#endif // _FEATHER52840_H