freedom-k64f

Tags: arch:arm chip:kinetis vendor:nxp

The Freescale / NXP Freedom K64F (FRDM-K64F) is an ultra-low-cost, compact development board designed for rapid prototyping with the NXP Kinetis K64 microcontroller family.

The board features the MK64FN1M0VLL12 MCU, built around an ARM Cortex-M4 core with hardware Floating Point Unit (FPU), running at up to 120 MHz with 1 MB of Flash memory and 256 KB of SRAM. The board is mechanically and electrically compatible with the Arduino Uno Revision 3 (R3) form factor.

Key Features

  • Microcontroller: NXP Kinetis MK64FN1M0VLL12 (100-pin LQFP) - 32-bit ARM Cortex-M4 with single-precision hardware FPU - Core clock frequency up to 120 MHz - 1 MB dual-bank embedded Flash memory (with read-while-write capability) - 256 KB SRAM - Hardware Cryptographic Acceleration Unit (CAU) and Random Number Generator (RNGB)

  • Ethernet: - Onboard 10/100 Mbps RMII Ethernet PHY (Micrel / Microchip KSZ8081RNA) - Integrated RJ-45 connector with built-in magnetics

  • Mass Storage: - Push-push MicroSD memory card slot connected to SDHC (4-bit SDIO interface) - Dedicated card-detection switch on pin PTE6

  • USB: - Dual-role Full-Speed USB 2.0 Device/Host controller with Micro-B USB connector - Crystal-less USB operation capability

  • Sensors: - NXP FXOS8700CQ 6-axis sensor (3-axis digital accelerometer and 3-axis digital magnetometer) - Connected via I2C bus 0 (I2C0)

  • User Interface: - Tricolor (RGB) user LED (Red on PTB22, Blue on PTB21, Green on PTE26) - Two user pushbuttons: SW2 (PTC6) and SW3 (PTA4 / NMI) - Dedicated system reset pushbutton (SW1)

  • Debug & Programming (OpenSDAv2): - Onboard Freescale OpenSDAv2 circuit running CMSIS-DAP / mbed bootloader firmware - Mass Storage Device (MSD) drag-and-drop flash programming - Virtual Serial Port (VCOM) over USB for the default NuttShell console - CMSIS-DAP debug interface for run-control and GDB debugging

  • Expansion Connectors: - Arduino R3 compatible footprint outer header pins - Additional inner row headers for full MCU I/O breakout - Footprint for 2.4 GHz RF module (Nordic nRF24L01+) and Bluetooth module

Hardware Configuration

Serial Console

The Kinetis K64 provides multiple UART modules. NuttX supports two primary serial console configurations:

USB VCOM Console (Default)

The default serial console uses UART0, which is routed directly to the onboard OpenSDAv2 microcontroller:

  • RX: PTB16 (UART0_RX)

  • TX: PTB17 (UART0_TX)

  • Baud rate: 115200 8N1

Connecting the OpenSDA micro-USB port (J26) to a host PC exposes a virtual serial port (e.g., /dev/ttyACM0 on Linux or COMx on Windows), giving immediate access to the NuttShell prompt without requiring external FTDI adapters.

Arduino Shield Serial Console

Alternatively, UART3 is routed to the Arduino R3 standard header pins on connector J1:

  • UART3_RX: PTC16 (Arduino Pin D0 / J1 Pin 2)

  • UART3_TX: PTC17 (Arduino Pin D1 / J1 Pin 4)

  • Baud rate: 115200 8N1

This interface allows attaching standard Arduino serial shields or RS-232 / TTL expansion boards.

Switching Console to UART3 (Arduino Shield)

To switch the primary serial console from OpenSDA (UART0) to the Arduino shield pins on UART3, configure the following settings via make menuconfig:

# Disable UART0 as serial console
CONFIG_KINETIS_UART0 is not set
CONFIG_UART0_SERIAL_CONSOLE is not set

# Enable UART3 as serial console
CONFIG_KINETIS_UART3=y
CONFIG_UART3_SERIALDRIVER=y
CONFIG_UART3_SERIAL_CONSOLE=y
CONFIG_UART3_RXBUFSIZE=256
CONFIG_UART3_TXBUFSIZE=256
CONFIG_UART3_BAUD=115200
CONFIG_UART3_BITS=8
CONFIG_UART3_PARITY=0
CONFIG_UART3_2STOP=0

RGB LED

The FRDM-K64F provides an onboard tricolor (RGB) LED. The cathodes are connected to MCU GPIO pins, so driving a pin low illuminates the corresponding color:

LED

K64 Port Pin / Function

RED

PTB22 / SPI2_SOUT / FB_AD29 / CMP2_OUT (Active Low)

BLUE

PTB21 / SPI2_SCK / FB_AD30 / CMP1_OUT (Active Low)

GREEN

PTE26 / ENET_1588_CLKIN / UART4_CTS_b / RTC_CLKOUT (Active Low)

When CONFIG_ARCH_LEDS is enabled, NuttX indicates kernel state using the RGB LED:

Symbol

Meaning

RED

GREEN

BLUE

LED_STARTED

NuttX has started

OFF

OFF

OFF

LED_HEAPALLOCATE

Heap allocated

OFF

OFF

ON

LED_IRQSENABLED

Interrupts enabled

OFF

OFF

ON

LED_STACKCREATED

Idle stack created

OFF

ON

OFF

LED_INIRQ

Handling an interrupt

N/C

N/C

N/C

LED_SIGNAL

Inside signal handler

N/C

N/C

N/C

LED_ASSERTION

Assertion failed

N/C

N/C

N/C

LED_PANIC

Kernel crash / panic

FLASH

OFF

OFF

During normal operation, the green LED remains illuminated. In the event of a fatal kernel panic, the red LED flashes.

User Pushbuttons

The board includes two user pushbuttons:

Switch

Port Pin

Features

SW2

PTC6 / LLWU_P10

User button, Low-Leakage Wake-up unit input

SW3

PTA4 / NMI_b / LLWU_P3

User button, Non-Maskable Interrupt, Wake-up

Note

Pin PTA4 is multiplexed with the Cortex-M4 Non-Maskable Interrupt (NMI). By default, NuttX configures PTA4 as a standard GPIO with pull-up.

Ethernet (KSZ8081RNA PHY)

The onboard Micrel / Microchip KSZ8081RNA Ethernet PHY connects to the K64 Ethernet MAC via Reduced Media Independent Interface (RMII):

PHY Signal

Board Net Name

K64 Port Pin

Pinmux Function

MDIO

RMII0_MDIO

PTB0

PIN_RMII0_MDIO

MDC

RMII0_MDC

PTB1

PIN_RMII0_MDC

RXD0

RMII0_RXD_0

PTA13

PIN_RMII0_RXD0

RXD1

RMII0_RXD_1

PTA12

PIN_RMII0_RXD1

CRS_DV

RMII0_CRS_DV

PTA14

PIN_RMII0_CRS_DV

RXER

RMII0_RXER

PTA5

PIN_RMII0_RXER

REF_CLK

RMII_RXCLK

PTA18 / EXTAL0

50 MHz Clock Input

TXEN

RMII0_TXEN

PTA15

PIN_RMII0_TXEN

TXD0

RMII0_TXD_0

PTA16

PIN_RMII0_TXD0

TXD1

RMII0_TXD_1

PTA17

PIN_RMII0_TXD1

RST_B

PHY_RST_B

Reset line

Active Low

Important

The FRDM-K64F board does not provide an external pull-up resistor on the MDIO signal line. Therefore, the internal pull-up resistor on the MCU must be enabled via CONFIG_KINETIS_ENET_MDIOPULLUP=y in the NuttX configuration.

MicroSD Card Slot (SDHC)

A push-push MicroSD slot connects directly to the K64 SD Host Controller (SDHC) over a 4-bit SDIO interface:

SD Card Net

Board Signal

K64 Port Pin

DAT0

SDHC0_D0

PTE1

DAT1

SDHC0_D1

PTE0

DAT2

SDHC0_D2

PTE5

CD/DAT3

SDHC0_D3

PTE4

CMD

SDHC0_CMD

PTE3

CLK

SDHC0_DCLK

PTE2

CARD_DETECT

D_CARD_DETECT

PTE6 (Active Low switch)

Using the MicroSD Card

Once booted, the SD card block driver registers at /dev/mmcsd0.

Manual Mount and Unmount:

# Mount FAT filesystem to /mnt/sdcard
nsh> mount -t vfat /dev/mmcsd0 /mnt/sdcard

# List files and read contents
nsh> ls /mnt/sdcard
nsh> cat /mnt/sdcard/test.txt

# Always unmount before removing the card
nsh> umount /mnt/sdcard

Note

If the mount command returns mount failed: 19, this corresponds to POSIX error ENODEV (No such device), indicating that no MicroSD card is present in the slot.

Auto-Mounter Configuration

NuttX provides an automated filesystem mounter that detects insertion and removal via the card-detect switch on pin PTE6:

CONFIG_FS_AUTOMOUNTER=y
CONFIG_FRDMK64F_SDHC_AUTOMOUNT=y
CONFIG_FRDMK64F_SDHC_AUTOMOUNT_FSTYPE="vfat"
CONFIG_FRDMK64F_SDHC_AUTOMOUNT_BLKDEV="/dev/mmcsd0"
CONFIG_FRDMK64F_SDHC_AUTOMOUNT_MOUNTPOINT="/mnt/sdcard"
CONFIG_FRDMK64F_SDHC_AUTOMOUNT_DDELAY=1000
CONFIG_FRDMK64F_SDHC_AUTOMOUNT_UDELAY=2000

With the auto-mounter enabled, inserting a MicroSD card mounts the FAT filesystem at /mnt/sdcard automatically, and removing it unmounts the volume.

Warning

While the auto-mounter automatically unmounts the volume upon detecting card removal via the card-detect switch, this occurs after the card has already begun disconnecting. If the card is physically removed while write operations or cache flushes are in progress, data loss or filesystem corruption can still occur. Users should always ensure all files are closed and flush/unmount the filesystem before physically extracting the MicroSD card.

Flashing and Debugging

The FRDM-K64F features the OpenSDAv2 multi-function debug interface. There are several methods for flashing and debugging NuttX firmware:

OpenSDAv2 Mass Storage Device (MSD) Drag-and-Drop

  1. Build NuttX to generate a raw binary image (nuttx.bin):

    ./tools/configure.sh freedom-k64f:nsh
make -j$(nproc)

  2. Connect a micro-USB cable between your host computer and the OpenSDA USB port (J26, labeled SDA).

  3. The board mounts on your host system as a removable mass-storage device named FRDM-K64F or MBED.

  4. Copy nuttx.bin onto the drive:

    cp nuttx.bin /media/$USER/FRDM-K64F/

  5. The OpenSDA status LED blinks during programming. Once complete, the board resets automatically and begins executing NuttX.

pyOCD (CMSIS-DAP)

pyOCD is an open-source tool for programming and debugging ARM Cortex-M microcontrollers over CMSIS-DAP:

# Flash the binary
pyocd flash -t k64f nuttx.bin

# Or start a GDB debug server on port 3333
pyocd gdbserver -t k64f

OpenOCD

You can also use OpenOCD via the CMSIS-DAP interface:

openocd -f interface/cmsis-dap.cfg -f target/kx.cfg \
        -c "program nuttx.bin 0x00000000 verify reset exit"

Supported Configurations

The board configurations for the FRDM-K64F are located under boards/arm/kinetis/freedom-k64f/configs/.

nsh

The default NuttShell (NSH) configuration provides an interactive command-line interface over the OpenSDAv2 virtual serial port.

  • Console: UART0 (PTB16 RX / PTB17 TX) at 115200 8N1 via OpenSDA VCOM

  • Memory: 128 KB configured SRAM heap, ProcFS filesystem

  • Building:

    ./tools/configure.sh freedom-k64f:nsh
make -j$(nproc)
cp nuttx.bin /media/$USER/FRDM-K64F/

netnsh

Extends the NSH environment with full 10/100 Mbps Ethernet network support via the onboard KSZ8081 PHY.

  • Networking Features:

    • IPv4 TCP/IP and UDP protocol stacks

    • ICMP socket support for the NSH ping utility

    • Telnet daemon utility (CONFIG_NETUTILS_TELNETD=y)

    • TFTP client (tftpc) for network file transfers

    • HTTP web client (webclient) for wget commands

    • Dynamic DHCP client (dhcpc) or static IP configuration (default 10.0.0.2)

  • Network Bringup Options:

    • CONFIG_NETINIT_THREAD=y: Runs network bringup on an asynchronous background thread, preventing boot pauses when the network cable is disconnected.

    • CONFIG_NETDEV_PHY_IOCTL=y: Enables PHY link monitoring and carrier detection.

  • Building:

    ./tools/configure.sh freedom-k64f:netnsh
make -j$(nproc)
cp nuttx.bin /media/$USER/FRDM-K64F/

  • Network Verification:

    # From NSH prompt (via OpenSDA VCOM):
nsh> ifconfig
nsh> ping 10.0.0.1

    Note

    To enable an interactive remote NSH shell over Telnet, enable CONFIG_NSH_TELNET=y in make menuconfig. Once enabled, connect from a host terminal using telnet 10.0.0.2.

cdcacm

Configures the NuttShell console on OpenSDA UART0 while enabling the native K64 USB Micro-B port (connector J22) as a CDC/ACM serial device (/dev/ttyACM0).

  • Console: UART0 (OpenSDA VCOM) at 115200 8N1

  • USB Device: CDC/ACM virtual serial class driver (CONFIG_CDCACM=y)

  • Utilities: Builtin sercon and serdis commands to dynamically connect and disconnect the CDC/ACM interface

  • Peripherals: FlexTimer PWM (FTM0 channel 2) and SDHC MicroSD storage support

  • Building:

    ./tools/configure.sh freedom-k64f:cdcacm
make -j$(nproc)
cp nuttx.bin /media/$USER/FRDM-K64F/

  • Using the CDC/ACM Serial Interface:

    1. Connect a USB cable to the native K64 USB Micro-B port (J22).

    2. From the NSH prompt on the OpenSDA console, attach the USB device:

      nsh> sercon

    3. The host computer enumerates the serial device (e.g., /dev/ttyACM0 on Linux).

    4. To disconnect the USB device cleanly:

      nsh> serdis

demo

A comprehensive feature demonstration configuration enabling multiple onboard peripherals:

  • Features:

    • NSH console on OpenSDA UART0

    • FXOS8700CQ 6-axis accelerometer/magnetometer sensor example application (examples/fxos8700cq)

    • 10/100 Mbps Ethernet networking stack with DNS client and netcat

    • FTM0 PWM driver

    • SDHC MicroSD storage support

  • Building:

    ./tools/configure.sh freedom-k64f:demo
make -j$(nproc)
cp nuttx.bin /media/$USER/FRDM-K64F/