Created a custom board .h file using this:
#ifndef RBLNANO2_H
#define RBLNANO2_H
#ifdef __cplusplus
extern "C" {
#endif
#include "nrf_gpio.h"
// LEDs definitions for RBL NANO 2
#define LEDS_NUMBER 1
#define LED_OB 11
#define LED_START LED_OB
#define LED_STOP LED_OB
#define LEDS_ACTIVE_STATE 0
#define BSP_LED_0 LED_OB
#define LEDS_LIST { LED_OB }
#define BSP_LED_0_MASK (1<<BSP_LED_0)
#define LEDS_MASK (BSP_LED_0)
#define LEDS_INV_MASK LEDS_MASK
#define BUTTONS_NUMBER 0
#define RX_PIN_NUMBER 30
#define TX_PIN_NUMBER 29
#define CTS_PIN_NUMBER 28
#define RTS_PIN_NUMBER 2
#define HWFC true
#ifdef __cplusplus
}
#endif
#endif // RBLNANO2_H
cloned the uart example that works fine on nRF52-DK and modified the Makefile to use above .h file. Build with gcc goes OK. Downloaded resulting hex file to BLE Nano2 using MK-20 - appears to go OK. No output on console.
Not sure what to try next to discover why printfs not working. My current guess is that SDK does not produce the right hex file format for the MK-20 loader. Could also be something to do with clock speeds. Anyone used the nRF SDK with BLE Nano?