I believe that what geeks want to think of most when they see the word "development board" is "raspberry pie". Some people may ask, what is raspberry pie? Raspberry pie (Raspberry Pi) It is a development board about the size of a credit card. Despite its "petite" appearance, its "heart" is very powerful. It has video, audio and other functions, which can be described as "small as a sparrow, it has all the internal organs". Its original intention is to support computer science education in some backward areas with low-cost hardware and open source software. Because it has a good balance between performance and price, many hardware players also want to buy one to "practice".

Of course, the protagonist of this evaluation is not the international favorite "Raspberry Pie", but the veteran semiconductor industry global well-known enterprise Freescale Freedom Development platform One of the most cost-effective FRDM-K64F 。 Freedom Development platform It is the latest launch of Freescale based on Kinetis L series ARM   Cortex-M0+ Ultra low cost prototype development platform for core microcontroller. The boards of this platform have similar characteristics, such as Kinetis series MCU , equipped with Freescale sensor OpenSDA Debugging interface and compatibility Arduino  R3 It is a platform for evaluation and development of microcontrollers with miniaturization, low power consumption and high cost performance. We can often see it in various national youth intelligent hardware creative competitions.

Next, let's take a look at the structural details of this development board with me.

The package is very simple and environmentally friendly. It is wrapped in a drawer style kraft paper box. The design of the box is very good, which can be regarded as simple with a sense of geek.

The drawer style design is very simple and clear. Once you pull it out, you can see that the development board is placed in the middle space. The package card is a simple manual, and the overall design is very compact.

This is a low-cost development board, only the size of a card. PCB The double-layer circuit board is adopted, but its appearance design is very special, Dark Blue The four corners of the colored circuit board are designed with rounded corners, The electronic components are arranged in a compact and reasonable manner, and are well placed, It looks very beautiful.

There are also 4 plastic fixing feet on the back.

For details, we can see that the solder joints are very exquisite, and the details experience the workmanship.

FRDM-K64F The design of the development board is very novel, not only Dark Blue Chromatic PCB The board also has the following characteristics:

·On board Back The screen printing of two-dimensional code is printed on the surface circuit board, which is a very novel design. Scanning the two-dimensional code with a mobile phone can quickly find the development board web page.

·Freescale's OpenSDA Debugger (open embedded serial and debug adapter). This is the No two Model integrates Freescale OpenSDA Development board of, in FRDM-KL25Z Development board of On, we first met Freescale's board carrier with trans era significance OpenSDA The debugger not only facilitates the establishment of the entire development platform, but also provides a variety of serial communications, flash The mode of programming and debugging.

·Freedom Expansion interface of development board and Arduino  UNO R3 The expansion interfaces of the Arduino The expansion board of can be easily matched FRDM-K64F use.

FRDM-K64F Development board The core processor of is ARM Cortex-M0+ kernel Kinetis  KL2 series micro controller KL25Z128VLK4 。 Cortex-M0+ Processor vs Cortex-M0 The biggest difference is that the processor is calculated by three Level pipeline becomes two Level pipeline, further reducing power consumption.

The Kinetics L series is an ultra low power consumption microcontroller, which consumes very little power in standby time and supports lithium battery power supply. Of course, during debugging, power is supplied directly through the micro USB port. There are two micro usb interfaces on the development board. One is the interface of the OpenSDA debugger, and the other is the direct output of the KL25Z microcontroller.

FRDM-K64F Development board Another feature is that it also supports SD The card expansion makes the development board have more expansion space.

Put more detailed drawings, and various serial interfaces are integrated on the development board:

Collected on the official website FRDM-K64F Development board characteristic ：

· MK64FN1M0VLL12 MCU(120 MHz ， 1 MB Flash memory, 256 KB RAM , low power consumption, no crystal oscillator USB and one hundred Thin quad flat package with pins (LQFP))

· Dual purpose USB Interface, with Micro-B USB Connector

· RGB LED

· FXOS8700CQ Accelerometers and magnetometers

· Two user buttons

· Flexible power supply options - OpenSDAv2 USB 、 Kinetis K64 USB And external power supply

· Compatible with Arduino ™   R3 Of I/O Connectors are easily accessible MCU input / output

· Programmable OpenSDAv2 Debugging circuit, support CMSIS-DAP The interface software provides the following functions:

             1 、 Mass storage device (MSD) Flash programming interface

             2 、 CMSIS-D AP The debugging interface can be driven free USB HID Connection provides operation control debugging function, compatible IDE tool

                 3 、 Virtual serial port

             4 、 Open Source CMSIS-DAP software project

· Ethernet

· SDHC

· Additional RF module: nRF24L01+ Nordic 2.4GHz radio

· additional Bluetooth modular: JY-MCU BT Circuit board V1.05 BT

· Software support and application development are provided by Kinetis Software Development Suite (SDK) Yes. This is a comprehensive suite, including stable and reliable peripheral drivers, protocol stacks and middleware ( Alternate Sample Code Package / Example ) . Join Kinetis Software development kit network community Forum to obtain expert opinions and support.

Practical link: (Official website tutorial reading acceleration and magnetic sensor values is selected)

stay mbed There is one on the official website     Routines, importing into mbed After compiling, download to K64F Development board, open the serial port assistant.

It outputs six Line data, three line integer, three line floating point. Change to one line 。

The first few lines are the data read out on the table, followed by the data after swinging the development board.

Summarize feelings:

·mbed A large number of classes are used in. I like mbed also C++ Good foundation, can better understand.
·In addition, in the process of learning the development board, I felt that the metal of the mesh port and the socket were a little hot.