User Manual

Page 9
nRF51 Development Kit User Guide v1.0
4.2 Virtual COM port
The on-board Interface MCU features a Virtual COM port via UART.
• Flexible baudrate setting up to 1 Mbps
• Dynamic Hardware Flow Control (HWFC) handling
• Tri-stated UART lines while no terminal is connected
Table 1 shows an overview of the UART connections on nRF51422 and the interface MCU.
Table 1 Relationship of UART connections on nRF51422 and Interface MCU
The UART signals are routed directly to the Interface MCU. The UART pins connected to the Interface MCU is
tri-stated when no terminal is connected to the Virtual COM port on the computer.
Note: The terminal used must send a DTR signal in order to configure the UART Interface MCU pins.
The P0.08 (RTS) and P0.10 (CTS) can be used freely when HWFC is disabled on the nRF51422.
4.3 Interface MCU Firmware
The on board Interface MCU is factory programmed with an mbed compliant bootloader, this feature
enables the ability to swap interface FW between the factory preloaded SEGGER J-Link OB and the nRF51
mbed interface FW, see section 4.1 “IF Boot/Reset button” on page 8 on how to enter the bootloader.
To swap Interface MCU FW, simply drag the Interface image (.bin) into the mounted bootloader drive on the
connected computer and power cycle the board.
Both the nRF51 mbed interface FW and the J-Link OB image can be downloaded from
www.nordicsemi.com.
Note: If you have swapped to the mbed image and want to revert back to the J-Link image,
download the latest SEGGER J-Link software from www.segger.com and open a debug session
to update to the latest J-Link OB firmware version.
Note: The J-Link serial number is linked to the Interface MCU and will not change even when
swapping the Interface MCU FW, so it can be useful to write the serial number on a sticker on
the board.
nRF51422 Interface MCU
Default GPIO UART UART
P0.08 RTS CTS
P0.09 TXD RXD
P0.10 CTS RTS
P0.11 RXD TXD