NXP FRDM-K64F

Fig. 1. NXP FRDM-K64F, Arduino Uno R3 form factor, 81 x 53 mm. Hover or tap a signal to light up every pin that carries it.

• It takes Arduino shields mechanically and will be damaged by plenty of them. The I/O is 3.3 V and not 5 V tolerant, and IOREF reports 3.3 V. Any shield that drives a signal from its own 5 V rail puts 5 V into a 3.3 V pin.
• D8 moved between board revisions. Rev E and later route it to PTC12; Rev D and earlier use PTA0, which is also the SWD clock line. Code and overlays written for one revision quietly do the wrong thing on the other.
• The Arduino serial pins D0 and D1 are UART3, not the debug console. The console is UART0 on PTB16 and PTB17, which goes to the OpenSDA chip and out over the USB port.
• UART3 is shared three ways: the D0/D1 header pins, the Bluetooth HCI header, and the Ethernet IEEE 1588 timer pins PTC16 to PTC19. Enabling Ethernet and the header serial together will not work.
• I2C0 on D14 and D15 is shared with the on-board FXOS8700 accelerometer and magnetometer at address 0x1D. It is a real bus with real pull-ups, so extra devices are fine as long as the address does not clash.
• SPI0 follows the Arduino convention: D10 is chip select, D11 is MOSI, D12 is MISO, D13 is SCK. The microSD slot is on the same bus.
• OpenSDAv2 gives you drag-and-drop flashing over USB mass storage, a CMSIS-DAP debug interface and a serial console on one cable. No external programmer needed.
• There are extra pins outside the Arduino footprint, on the outer rows of the same headers, carrying the rest of the Ethernet and the CAN pins. Those are not shown here.

• Blink the red LED on PTB22

  CMSIS device headers

  #include "MK64F12.h"
  
  /* Kinetis splits this in two: SIM gates the clock, PORT muxes the
     pin, GPIO drives it. Miss the SIM line and the PORT writes do
     nothing at all. */
  SIM->SCGC5 |= SIM_SCGC5_PORTB_MASK;
  
  PORTB->PCR[22] = PORT_PCR_MUX(1);     /* ALT1 = plain GPIO */
  
  GPIOB->PDDR |= (1u << 22);            /* 1 = output */
  GPIOB->PCOR  = (1u << 22);            /* clear, LED on  */
  GPIOB->PSOR  = (1u << 22);            /* set,   LED off */
  GPIOB->PTOR  = (1u << 22);            /* toggle */

  PORT and GPIO are separate peripherals with separate clock gates. Writing PCR without first setting the SIM_SCGC5 bit silently does nothing, which looks exactly like a dead pin.

Table 1. Pin assignments.