NXP Semiconductors FRDM-KL28Z User manual

© 2016 NXP B.V.
FRDM-KL28Z User’s Guide
1.Introduction
The Freedom development platform is a set of software
and hardware tools for evaluation and development. It is
an ideal tool for the rapid prototyping of
microcontroller-based applications.
The FRDM-KL28Z supports power supply voltage
range from 1.71 V to 3.6 V. It features a KL28Z, a
device boasting a maximum operating frequency of 96
MHz, up to 512 KB Flash and numerous analog and
digital peripherals.
The FRDM-KL28Z includes the NXP open standard
embedded serial and debug adapter known as
OpenSDA. This circuit offers the user several options
for serial communications, flash programming and run-
control debugging.
The FRDM-KL28Z hardware is form-factor compatible
with the Arduino™ R3 pin layout, providing a broad
range of expansion board options. The on-board
interfaces include an RGB LED, a 6-axis digital sensor
(combining a 3D accelerometer and 3D magnetometer),
a 3-axis digital angular rate gyroscope, an ambient light
sensor, and a capacitive touch slider.
There are many software development tool options
available to the user. Choices include Kinetis Design
Studio (KDS), IAR Embedded Workbench, Keil MDK
featuring the µVision IDE, and so on.
All of these features combine to give users the freedom
needed to rapidly prototype many embedded designs: a
NXP Semiconductors
Document Number: FRDMKL28ZUG
User's Guide
Rev. 0
,
06/2016
Contents
1. Introduction ....................................................................1
2. Getting Started................................................................2
3. FRDM-KL28Z Features ..................................................2
4. FRDM-KL28Z Hardware Description..............................4
4.1. Power supply........................................................4
4.2. Serial and debug adapter (OpenSDA) ....................5
4.3. Microcontroller.....................................................7
4.4. Capacitive touch slider..........................................9
4.5. I2C Inertial Sensor..............................................10
4.6. RGB LED...........................................................11
4.7. Visible light sensor .............................................11
4.8. EMVSIM Header................................................12
4.9. SPI2 Header ....................................................... 13
4.10. Analog reference voltage.....................................13
4.11. Input/output headers............................................14
5. References....................................................................15
6. Revision History ...........................................................15

FRDM-KL28Z Features
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powerful microcontroller built on a very low-power core and SOC platform, easy-access to I/O with a
large ecosystem of compatible hardware, a flexible programming and debug interface, and a large
ecosystem of software development environments.
2.Getting Started
Refer to the FRDM-KL28Z Quick Start Package for step-by-step instructions for getting started with the
freedom board. See the “Jump Start Your Design” section at nxp.com/FREDEVPLA for the Quick Start
Package and software lab guides.
3.FRDM-KL28Z Features
The FRDM-KL28Z hardware is a Freedom development board assembled with the following features:
MKL28Z512VLL7 MCU (96 MHz, 512 KB Flash, 128 KB RAM, 32 KB ROM,100 LQFP
package)
3-Axis Digital Angular Rate Gyroscope, FXAS21002CQ (U2)
Accelerometer and magnetometer, FXOS8700CQ (U10)
OpenSDA: On-board serial and debug adapter (U7)
I/O headers for easy access to MCU I/O pins
Ambient light sensor (Q1)
Flexible power supply options: USB, coin cell battery, external source
Capacitive touch slider
Reset push button (SW1)
NMI and LLWU buttons (SW2, SW3)
RGB LED (D2)
The FRDM-KL28Z features two MCUs: The target MCU is the MKL28Z512VLL7. The OpenSDA
MCU is the MK20DX128VFM5.
The primary components and their location on the hardware assembly are pointed out in Figure 1.
Figure 2 shows a block diagram of the FRDM-KL28Z board.

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MK20DX128VFM5
KL28Z
Digital Angular
Rate Gyroscope
Accelerometer and
Magnetometer
Capacitive touch
slider
RGB LED
Open SDA USB KL28Z USB
SPI2 Header
Ambient Light
Sensor
Reset Push Button
LLWU button NMI button
Figure 1. FRDM-KL28Z feature call-outs
Figure 2. FRDM-KL28Z block diagram

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4.FRDM-KL28Z Hardware Description
4.1. Power supply
The FRDM-KL28Z offers a design with multiple power supply options. It can be powered from the
USB connector, battery on the board, the VIN pin on the I/O header, or an off-board 1.71-3.6 V supply
from the 3.3 V pin on the I/O header. The USB and VIN supplies are regulated on-board using a 3.3 V
linear regulator to produce the main power supply. Other sources are not regulated on-board.
The following table provides the operational details and requirements for the power supplies.
Table 1. Tags Power supply requirements
Supply Source & Location
Valid Range
OpenSDA Operational?
Regulated on-board?
OpenSDA USB (J13)
5 V
Yes
Yes
KL28Z USB (J10)
5 V
No
Yes
P5V0-9V0_VIN
(J3 PIN16)
4.3-9 V
No
Yes
P3V3 Pin（J3 PIN8）
1.71-3.6 V
No
No
Battery
2-3.6 V
No
No
Figure 3 shows the schematic drawing for the power supply inputs and the on-board voltage regulator.
In addition, regulated power can be supplied to J3 pin 16 from an external source through P5-9V_VIN
by populating the board with an optional voltage regulator (for instance a 7805 style regulator) in a TO-
220 package, thus providing a high current supply to external devices. To prevent voltage sag under a
high load, C34, C35, C36, and C37 should be populated with appropriately sized capacitors to match the
regulator chosen.
Figure 3. Power supply schematic

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NOTE
The OpenSDA circuit is operational only when a USB cable is connected
and supplying power to J13. However, the protection circuitry is in place
to allow multiple sources to be powered at once.
Table 2. FRDM-KL28Z power supplies
Power Supply Name
Description
P5V0-9V0_VIN
Power supplied from the VIN pin of the I/O headers (J3 pin 16).
P5V_SDA
Power supplied from the OpenSDA USB connector
P5V_USB
Nominal 5 V is supplied to the I/O headers (J3 pin 10). Sourced from either the P5V_KL28Z
or P5V_SDA through a back drive protection Schottky diode.
P5V_KL28Z
Power supplied from the Mini USB connector.
P3V3_VREG
Regulated 3.3 V supply. Sources power to the P3V3 supply rail through an optional back
drive protection Schottky diode.
P3V3
Main supply rail for the FRDM-KL28Z. Can be sourced from P3V3_VREG (J3 pin 8).
P3V3_KL28Z
KL28Z MCU power supply. Header J17 provides a convenient means for KL28Z energy
consumption measurements.
P3V3_SDA
OpenSDA circuit power supply.
P3V3_BATT
Coin cell battery supply voltage. Sources power to the P3V supply rail with the option of
adding a Schottky diode.
NOTE
J9 and J17 are populated by default. It is very convenient to measure the
energy consumption of the KL28Z by a parallel voltmeter or a series
ammeter.
4.2. Serial and debug adapter (OpenSDA)
OpenSDA is an open-standard serial and debug adapter. It bridges serial and debug communications
between a USB host and an embedded target processor as shown in Figure 4. OpenSDA features a mass
storage device (MSD) bootloader, which provides a quick and easy mechanism for loading different
OpenSDA Applications such as flash programmers, run-control debug interfaces, serial-to-USB
converters, and more. Two or more OpenSDA applications can run simultaneously. For example, run-
control debug application and serial-to-USB converter runs in parallel to provide a virtual COM
communication interface while allowing code debugging via OpenSDA with just single USB
connection. These two applications are provided in a single code package. Refer to the OpenSDA User’s
Guide for more details.
OpenSDA is managed by a Kinetis K20 MCU built on the ARM Cortex-M4 core. The OpenSDA circuit
includes a status LED (D1) and a RESET pushbutton (SW1). The pushbutton asserts the Reset signal to
the KL28Z target MCU. It can also be used to place the OpenSDA circuit into bootloader mode by
holding down the RESET pushbutton while plugging the USB cable to USB connector J13. Once the
OpenSDA enters bootloader mode, other OpenSDA applications such as debug app can be programmed.
SPI and GPIO signals provide an interface to the SWD debug port of the KL28Z. Additionally, signal
connections are available to implement a UART serial channel. The OpenSDA circuit receives power
when the USB connector J13 is plugged into a USB host.

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Figure 4. OpenSDA block diagram
4.2.1. Debugging interface
Signals with SPI and GPIO capability are used to connect directly to the SWD of the KL28Z. These
signals are also brought out to a standard 10-pin Cortex Debug connector (J11) as shown in Figure 5.
In order to isolate the KL28Z MCU from the OpenSDA circuit and use J11 to connect to an off-board
MCU, cut the trace between pin1 and pin2 of J18 on bottom layer. This will disconnect the SWD_CLK
pin to the KL28Z so that it will interfere with the communications to an off-board MCU connected to
J11. Figure 5 shows SWD connector signals description for KL28Z.
Figure 5. SWD debug connector to KL28Z
4.2.2. Virtual serial port
A serial port connection is available between the OpenSDA MCU and pins PTB16 and PTB17 of the
KL28Z.Several of the default OpenSDA applications provided by Freescale, including the MSD Flash
programmer and the P&E debug application, providing a USB communications device class (CDC)
interface that bridges serial communications between the USB host and this serial interface.

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4.3. Microcontroller
The FRDM-KL28Z is a MCU module featuring the MKL28Z512VLL7, a Kinetis microcontroller with
USB 2.0 full-speed OTG controller in a 100 LQFP package. An on-board debug circuit, OpenSDA,
provides a SWD interface and a power supply input through a mini-USB connector, as well as serial to
USB and CDC class compliant UART interface. The KL28Z MCU features as shown in Table 3.
Table 3. Features of MKL28Z512VLL7
Feature
Description
Ultra-low-power
- 10 low-power modes with power and clock gating for optimal peripheral activity and
recovery times. Stop currents of <190 nA (VLLS0), run currents of <280 uA/MHz, 4 s wake-
up from Stop mode
- Full memory and analog operation down to 1.71V for extended battery life
- Low-leakage wake-up unit with up to eight internal modules and eight pins as wake-up
sources in low-leakage stop (LLS)/very low-leakage stop (VLLS) modes
- Low-power timer for continual system operation in reduced power states
Flash, SRAM, ROM
- 512 KB flash featuring fast access times, high reliability, and four levels of security
protection. No user or system intervention to complete programming and erase functions
and full operation down to 1.71 V
- 128 KB of SRAM
- 32 KB of ROM with Kinetis bootloader included (UART, SPI, I2C, USB-HID)
Mixed-signal
capability
- SAR 16-bit analog-to-digital converter (ADC)
- High-speed comparator (CMP) with internal 6-bit digital-to-analog converter (DAC)
- 12-bit digital-to-analog converter (DAC)
- VREF module 1.2 V output
Performance
- 72 MHz ARM Cortex-M0+ core
- Up to 16 channel DMA for peripheral and memory servicing with reduced CPU loading
and faster system throughput
- Cross bar switch enables concurrent multi-master bus accesses, increasing bus
bandwidth
- Independent flash banks allowing concurrent code execution and firmware updating with
no performance degradation or complex coding routines
- Bit manipulation engine (BME) allows execution of single-instruction atomic bit-modify-
write operations on the peripheral address space
Timing and control
- Three timer/PWM modules –one with six channel, and two with two channels
- Low-power timer
- Real-time clock
- 4-channel 32-bit periodic interrupt timer provides time base for RTOS task scheduler or
trigger source for ADC conversion, provides lifetime timer capability
Human-machine
interface
Connectivity and
communications
- Touch sensing input
- General-purpose input/output up to 54
- USB full-speed OTG controller with on-chip transceiver and 5 V to 3.3 V regulator,
supporting crystal-less recovery
- USB low-voltage regulator supplies up to 120 mA off chip at 3.3 volts to power external
components from 5-volt input
- Three 32-bit LPSPI modules
- Three LPUART modules
- Three LPI2C modules supporting Ultra-Fast mode
- One I2S (SAI) module
- FlexIO module

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4.3.1. Clock source
KL28Z start up to the default reset clock for core/system clock, which is 8 MHz from SIRC. Software
can enable the main external oscillator (EXTAL/XTAL), or to high frequency internal reference (FIRC)
48 MHz if desired. The external oscillator/resonator can range from 32.768 KHz up to 32 MHz. A
32.768 KHz crystal is the default external source for the SCG oscillator inputs (XTAL/EXTAL).
4.3.2. Serial port
The primary serial port interface signals are PTB16 and PTB17. These signals are connected to both the
OpenSDA and to the J1 I/O connector. Note that the OpenSDA connection can be isolated from J1 by
removing R47 and R48, if required.
4.3.3. USB port
The Kinetis KL28 microcontroller features a dual-role USB controller with on-chip full-speed and low-
speed transceivers. The USB interface on the FRDM-KL28Z is configured as a full-speed USB device.
J10 is the USB connector for this interface. As shown in Figure 6.
Figure 6. USB connector schematic

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4.3.4. Reset
The PTA20/RESET signal on the KL28Z is connected externally to a pushbutton, SW1, and also to the
OpenSDA circuit. However, R76 should be removed when isolating the OpenSDA MCU from SW1 or
to do power consumption testing for KL28Z. Isolating the RESET line allows a more accurate
measurement of the target device’s power consumption in low-power modes. The reset button can be
used to force an external reset event in the target MCU.
4.3.5. Debug
The sole debug interface on all Kinetis L series devices is a Serial Wire Debug (SWD) port. The primary
controller of this interface on the FRDM-KL28Z is the onboard OpenSDA circuit. However, a 2x5-pin
Cortex Debug connector, J11, provides access to the SWD signals for the KL28Z MCU. The following
table shows SWD connector signals description for KL28Z.
Table 4. ARM JTAG/SWD mini connector description
Pin
Function
Connection to KL28Z
1
VTref
P3V3_MCU
2
SWDIO/TMS
PTA3
3
GND
GND
4
SWDCLK/TCK
PTA0
5
GND
GND
6
SWO/TDO
NC
7
NC
NC
8
TDI
NC
9
NC
NC
10
RESET
PTA20
4.4. Capacitive touch slider
Two GPIO pins functioning as Touch Sense Input (TSI) signals, are connected to capacitive electrodes
configured as a touch slider as shown in Figure 7.
Figure 7. Touch slider connection

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4.5. I2C Inertial Sensor
4.5.1. 6-axis accelerometer and magnetometer
FXOS8700CQ is a small, low-power, 3-axis, linear accelerometer, and 3-axis magnetometer combined
into a single package. The device features a selectable I2C or point-to-point SPI serial interface with
14-bit accelerometer and 16-bit magnetometer ADC resolution along with smart-embedded functions. It
is interfaced through an I2C bus and two GPIO signals as shown in Figure 8 and the table below.
By default, the I2C address is 0x1E (As SA0 and SA1 were pulled low).
Figure 8. FXOS8700CQ schematic diagram
Table 5. Accelerometer FXOS8700CQ signal connections
FX0S8700CQ
KL28Z
SCL
PTE24
SDA
PTE25
INT1
PTD4
INT2
PTE5
4.5.2. 3-Axis Digital Angular Rate Gyroscope
FXAS21002C is a small, low-power, pitch, and roll angular rate gyroscope with 16 bit ADC resolution.
The full-scale range is adjustable from ±250°/s to ±2000°/s. It features both I2C and SPI interfaces. It is
interfaced through an I2C bus and two GPIO signals as shown in the following table and Figure 9. By
default, the I2C address is 0x20 (As SA0 pulled low).
Table 6. Gyroscope FXAS21002CQ signal connections
FXAS21002CQ
KL28Z
SCL
PTE24
SDA
PTE25
INT1
PTE0
INT2
PTE1