Datasheet

FRDMKL25ZUM FRDM-KL05Z User's Manual Page 7 of 13
5.2 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. The hardware circuit is
based on a Freescale Kinetis K20 family microcontroller (MCU) with 128 KB of embedded flash and an
integrated USB controller. 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. Refer to the OpenSDA User’s Guide
for more details.
Figure 4. OpenSDA High-Level Block Diagram
The OpenSDA circuit includes a status LED (D1) and a pushbutton (SW1). The pushbutton asserts the
Reset signal to the KL05Z target MCU. It can also be used to place the OpenSDA circuit into Bootloader
mode. SPI and GPIO signals provide an interface to the SWD debug port of the KL05Z. Additionally,
signal connections are available to implement a UART serial channel. The OpenSDA circuit receives
power when the USB connector, J2, is plugged into a USB host.
5.2.1 Debug Interface
Signals with SPI and GPIO capability are used to connect directly to the SWD of the KL05Z. These
signals are also brought out to a standard 10-pin (0.05”) Cortex Debug connector (J1). It is possible to
isolate the KL05Z MCU from the OpenSDA circuit and use J1 to connect to an off-board MCU. To
accomplish this, cut the trace on the bottom side of the PCB that connects J6 pin 1 to J6 pin 2. This will
disconnect the SWD_CLK pin to the KL05Z so that it will not interfere with the communications to an
off-board MCU connected to J1.