"Freedom development board is an important MCU development platform after Freescale introduced arm Cortex-M series processor. The boards of this platform have similar characteristics, such as based on kinetis Series MCU, equipped with Freescale sensor, opensda debugging interface and compatible with third-party expansion interface. It is a miniaturized, low-power A cost-effective platform for microcontroller evaluation and development.
In the past evaluation articles of aiban.com, we have learned about the microcontroller boards of freedom platform based on kinetis L and kinetis e series. Today, we will introduce the latest development board of freedom platform based on kinetis K series microcontrollers launched by Freescale - frdm-k22f provided by e-alliance electronics. I believe you are no stranger to e-alliance (element14), This is a leading distributor of electronic components in the industry. It often launches some characteristic boards with semiconductor manufacturers. Interested engineers can often pay attention to it. The current quotation of the frdm-k22f card obtained by the author in E Luomeng electronics is 204.7rmb.
Frdm-k22f development board
Frdm-k22f development board inherits the exquisite and simple drawer packaging of Freescale freedom platform, as shown in the figure below.
However, the board this time gives people a lot of surprises. First of all, from the appearance, frdm-k22f belongs to an eye-catching orange, which is cool and energetic. In retrospect, it seems that Freescale's freedom boards of each series are different in color, very characteristic and full of personality. However, the author still believes that frdm-k22f is one of the most exquisite and beautiful of all freedom cards at present.
You might as well learn more about frdm-k22f.
Frdm-k22f is a 4-layer board design, with a size of about 81mm * 53mm, which is smaller than the business card. The four corners of the whole board are still in the arc design style of the freedom platform, and the four corners are polished very smoothly, with fingers crossed without any burr. This situation is rarely seen on a development board (except ATMEL board).
Whether it is the overall design layout or workmanship of the board, frdm-k22f presents an interpretation of "beauty without friends", even if it is called a work of art in the development board. Of course, if the frdm-k22f is only "bubbling in beauty" and has no matching performance or function, it can only be reduced to a vase. So, let's focus on the onboard resources.
Frdm-k22f Freescale kinetis K series microcontroller mk22fn512vlh12 based on arm cortex-m4 core focuses on USB application field without external crystal oscillator. It carries a new opensdav2.1 debugger and supports arm mbed project. The board is equipped with rich development functions such as acceleration sensor and magnetometer, RGB LED and expansion interface of Arduino uno R3.
Frdm-k22f development board features:
Mk22fn512vlh12 MCU - 120 MHz, 512 KB flash memory, 128 KB ram, crystal free USB, 64 LQFP package
Two microusb interfaces - opensdav2.1 USB, k22f USB
One RGB LED
An accelerometer and magnetometer FXOS8700CQ
Two user buttons, one reset button
Flexible power supply options - opensdav2.1 USB, k22f USB or external power supply
Arduino uno R3 compatible extension interface
Programmable opensdav2.1 debugger
Optional microSD card slot for operation via SPI
Optional additional RF module connector: nRF24L01 + Nordic 2.4 GHz wireless communication
Optional additional Bluetooth module connector: jy-mcu BT circuit board v1.05 BT
Support arm mbed
Among the many features on the frdm-k22f development board, the most confusing place may be the functions of the two microusb interfaces on the board. First, we can simply distinguish the two microusb interfaces into k22f-usb interface and opensdav2.1 debug USB interface.
The k22f-usb interface realizes the USB device function of k22f microcontroller by default, but at the same time, it can realize the virtual serial port function by installing the USB CDC driver. Not only that, we can realize the USB host function of k22f microcontroller through the on-board USB host 5V enable skipping cap (as shown in the figure below). Is it very powerful.
In addition, the opensda2.1 debug USB interface has more functions. When we actually use the k22f development board, we basically can't do without it, whether downloading or debugging. Several main features of the opensda2.1 debug USB interface are as follows:
Flash programming interface of mass storage device (MSD) (i.e. bootloader mode. For specific operation, please refer to the evaluation of frdm-kl25z development board)
Cmsis-dap debugging interface, AMR standard embedded debugging interface
Open source hardware design, open source bootloader, open source firmware
Realize arm mbed flash programming function
Virtual serial port function
For friends who first contact Freescale freedom development platform, it takes some time to get familiar with the functions of these two microusb, but when all the functions are "played between the palm of your hand", you can completely avoid the third-party debugging tools for complete project development.
Another distinctive feature of the frdm-k22f development board is that the board has a "backup" function. If you carefully observe it, you can find that the board has many devices that are not pasted, such as audio circuit, microSD card, etc., and even reserved many interfaces with optional functions, such as RF module interface and Bluetooth module interface as shown in the figure below, This can also be regarded as a very rich "extended function" reserved for DIY in the future.
Microcontroller mk22fn512vlh12
The core of frdm-k22f development board is Freescale kinetis K series microcontroller mk22fn512vlh12 at the center of the board, which is packaged with lqfp-64 and has a size of 10mm * 10mm. The main feature of this series of microcontrollers is to support crystal free USB design, which can reduce system cost and save circuit board space.
Characteristics of microcontroller mk22fn512vlh12:
Arm cortex-m4 core, DSP instruction system, 1.25 Dhrystone MIPS / MHz, 512 KB on-chip flash and 128 KB RAM
3 internal oscillators: 32 kHz, 4 MHz and 48 MHz
Two 8-channel motor control / Universal / PWM timers
Two 2-channel motor control / Universal timers with quadrature decoder function
Two 16 bit SAR ADCs with a conversion rate of 1.2ms/s and two 12 bit DACs in 12 bit mode
Two analog comparators (CMP) with 6-bit DAC
USB full speed / low speed on the go controller with on-chip transceiver and 120 mA USB LDO Regulator
Two SPI modules, three UART modules and one low-power UART, I2S module
Two I2C modules: capable of supporting 400 kbit / s operation
Up to 40 IOS scalable
From the system block diagram of mk22fn512vlh12 microcontroller, we can intuitively understand the performance and function of this MCU. The whole microcontroller is composed of 9 units, including high-performance core processor arm coretex-m4, system peripherals, memory and storage interface, clock, security module, simulation module, timer, communication interface and man-machine interface. From the introduction of the characteristics of the microcontroller mk22fn512vlh12, we can also understand the detailed functions of each unit, which will not be repeated here.
The characteristics of mk22fn512vlh12 microcontroller determine its rich application scenarios, such as the current popular smartphone peripheral accessories: Mini Bluetooth headset, smart power supply, apple speaker and other solutions. The following figure is a simple hardware block diagram of wireless music player designed based on K22 series microcontroller.
How to develop
To further understand the frdm-k22f development board, hands-on operation is the most effective way. Frankly, Freescale frdm-k22f supports many integrated development tools, such as IAR, KEIL, CodeWarrior, KDS, mbed, etc. engineers can choose the corresponding tools according to their usage habits. For friends who first contact the development board, it is recommended to use the combination of KDS + mbed online ide tools. First of all, these two are free tools. There is no use restriction and no cost. They can also be used complementary without conflict. KDS is suitable for the development of complete projects, including code editing, compiling, downloading and debugging. In addition to debugging, mbed ide online tools are very convenient for editing, compiling and downloading. It can be said that they can be used where there is a network without installation.
As for the frdm-k22f hardware debugging tool, there is no dispute. It is most convenient and easy to directly use the on-board opensdav2.1 debugger. Of course, frdm-k22f also supports the idea of "money can be arbitrary". You can also use a third-party hardware debugging tool for ARM kernel for board development, such as j-link. The specific use of each ide tool will not be introduced here. Please refer to the relevant operation instructions in the past evaluation articles of aiban.com:
The principle introduction and use of opensda debugger can refer to the evaluation of frdm-kl25z development board
For the introduction of KDS, please refer to sd-fsl-kl25evb development board evaluation. Pay attention to selecting the corresponding MCU version when downloading KDS software
For the introduction of ARM embedded project, please refer to the evaluation of stm32f401 nucleus development board
However, the opensdav2.1 debugger installed on frdm-k22f should be mentioned here. On the development board of frdm-kl25z, we first came into contact with the birth of Freescale's Cross era opensda debugger, which uses the USB device mode to burn code, eliminating the need to install additional debugger drivers, And its firmware update and stability are very convenient and commendable, but the so-called opensda is not as open as it was named in the first generation and is not open source.
Then, on the frdm-k64 development board launched by Freescale, the opensda debugger has been updated to the opensda V2 version. At this time, on the frdm-k22f development board obtained by aiban.com, the debugger has been updated to the opensdav2.1 version, which is not different from the V2 version, but compared with the opensda generation, Except that there are no significant changes in the hardware circuit (some level logic conversion is added, which is applicable to some higher-end MCU, and 2.5V, 1.8V and other levels can be used), the firmware is completely upgraded and replaced with an open-source cmsis-dap debugger, which solves the open-source problem of bootloader and all applications (debug, virtual serial port, MSD, etc.).
In addition, the file format of the firmware and application of opensda v2.1 is changed to. Bin file, which is no longer the original. S19 and. SDA format. It should be noted that if the downloaded code is confused, it cannot run.
In addition, segger's official website also provides j-link firmware support for Freescale opensdav2.1 debugger to support j-link Lite, allowing users to use some features of j-link, such as ultra fast flash download and debugging, and GDBSERVER. For details, please refer to opensda v2.1 firmware.
After knowing the basic environment of frdm-k22f development board, we can officially develop the board. Relevant step-to-step operations are described in the rapid development package provided by Freescale, which will not be described in detail here.
At the first power on meeting of frdm-k22f development board, the demo program provided by the board will be run, including bubble level meter, electronic compass, USB CDC demonstration, metal detector, timer and wireless mouse function demonstration. The specific operation can be carried out step by step through the printed content output from microusb debug serial port (serial port driver download). Interested friends can go to e-league to buy the board and experience it personally, Next, this paper will introduce how to realize the quickest start-up operation and download routine of frdm-k22f.
When the microusb debug interface of frdm-k22f development board is powered on, an mbed drive with 512KB free space will appear on the computer. Click the mbed.htm file, and then you can quickly enter the mbed platform development environment.
Mbed online ide tool has been introduced many times in the evaluation articles of aiban.com, but most of them are for ST's nucleus series cards. For Freescale cards, this is the first time to officially use mbed online ide tool.
The bin file compiled by the above routine code can be directly copied to the mbed drive letter to complete the burning of flash program. As expressed in the code, the color of RGB LED display can be switched through the two user keys SW2 and SW3, and the corresponding character output will appear on the serial port. The fastest flash programming development of frdm-k22f development board can be realized through the online mbed tool. The following figure shows the operation of the development board after pressing the SW3 user key.
Note: if the mbed drive does not appear on the PC when connecting the frdm-k22f development board for the first time, you need to start the bootloader function of opensdav2.1. At this time, you can press and hold the reset button, and then power up the development board through the microusb debug interface to display a message on the computer
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