Many suppliers are now creating MCU development kits targeted for specific applications. Unlike the more generic kits, which are primarily focused on general educational activities and typically include simple LED-blinking examples, targeted development kits provide enough hardware and software to give you a significant head start on an actual design. Kits targeted for motor control, smart energy metering, healthcare monitoring, audio processing, and a host of other applications can dramatically speed your time-to-market.
In order to create these types of kits, manufacturers have selected different strategies, each with their advantages and disadvantages. Some suppliers create a specific hardware-optimized board, while others build very generic MCU motherboards with a variety of add-on modules that can be used to create application-targeted bundles. Understanding these strategies and the associated advantages and disadvantages will allow you to better select the appropriate development kit for your design requirements. After describing the most common types of development kit strategies, we will look at some typical example designs to see how they are implemented with some readily available development kits.
The modular platform-based approach
The platform-based approach is a common strategy for manufacturers to use since it typically is very cost effective. Usually a somewhat generic MCU board with little on-board dedicated hardware is used as the starting point. The board has a significant amount of standard interface connectors to accommodate all the various peripherals and general-purpose I/Os from the device. A mechanical standard for the interface connectors makes it possible to create easy to plug-in add-on cards for various peripherals. If you want an Ethernet connection, just get the Ethernet add-on module that translates the interface connector, along with any required magnetics or other physical layer components, to an Ethernet jack. These interface breakout boards can be very inexpensive, while allowing a significant amount of configurability.
Many manufacturers provide add-on modules for companion devices, too. Want an accelerometer? That is probably available as an add-on card. Most add-on cards also come with the drivers and example software routines necessary to add the desired functionality to an existing system. In some cases, the example code is actually part of a reference design, which makes it even easier to get a head start on your project.
You can see how manufacturers benefit from the platform-based approach. Add-on cards can be used in multiple reference designs, which leverages the development cost over multiple target applications. The effort put into driver development, testing, and higher-level functions can be leveraged over multiple application targets as well, typically with minimal modification. When the manufacturer includes some of their own companion devices, perhaps analog converters, memory, physical layer components, or even passives on the add-in card, they can create even more potential sales opportunities. Additional sales opportunities can help justify the development cost of the various boards, firmware, and supporting material.
An example modular platform: The Freescale Tower System
An example of a platform-based approach is clearly illustrated by the Freescale
Tower System. This modular approach (Figure 1) uses one or two side boards to connect a main board and up to three add-on boards. Main boards also feature a top-pluggable connector so that compatible plug-in modules, featuring keypads, accelerometers, or rotary touchpads, can be added without using up valuable add-on board slots. Notice that the side board can have additional connectors so that side-mounted peripheral boards, such as an LCD board, can be used if more functionality is required. The modular design approach makes it easy to construct a system with nearly any combination of features.
Figure 1: The Tower System Modular Development Platform from Freescale.
The tower system can be used with a wide variety of controller/processor modules that feature 8-, 16-, and 32-bit Freescale MCUs and MPUs. These controller modules provide easy-to-use starting points for the design. Many common peripherals, including USB and serial port connectors, are native on the controller module so that only the application-specific peripherals will need to use add-on boards.
The tower system includes software so you can leverage low-level drivers and APIs, as well as RTOS, TCP/IP, USB stacks, and file systems. Extensive example routines and reference designs are also available so that creating your software design can be a modular process, similar to that used to create the hardware platform.
A complete web server demonstration design (TWR-K60F120M-KIT
) can easily be created using hardware and software components for the tower system. The system can serve up web pages using the modular software stacks provided for each of the key functions. Sensor add-in boards can easily turn the web server into a network-based remote measurement and control system. A remote sensor control system can be prototyped and tested using the tower system’s convenient, if somewhat unwieldy, form-factor, since there are usually minimal constraints on a remote sensor for field-testing. A wide variety of tests can be performed, however, and the modular implementation means that sensors and control interfaces can be reconfigured or swapped in and out to validate different functional combinations. The flexibility of the modular approach is a key strength when a variety of system configurations need to be tested either in the lab or in a field trial.
The dedicated approach
The dedicated approach for creating a targeted development platform is primarily different in its hardware implementation. The dedicated approach provides the hardware needed for the target application, with much less add-on capability than the modular platform approach. From a manufacturer’s perspective, the dedicated approach can require more effort, since a development using the modular approach can many times leverage previously developed modules. The advantage to the manufacturer, however, is that the target system can approach the final design much more closely. In fact, the designer may be able to use some of the board layout (which is typically provided by the manufacturer) and the bill of materials directly in the production design. If the manufacturer sources most of the components in the bill of materials, there is a good chance the designer will end up specifying all the manufacturers’ devices in the final production product.
One application area that typically uses the dedicated approach is for motor control. Applications with high-power requirements are often dedicated since the layout requirements for the high-power components, like a motor driver TRIAC, power converters, and the associated capacitors and inductors are often of key importance for reliable operation. The STEVAL-IHM029V1
2,000 W universal motor controller from STMicroelectronics
(Figure 2) is a good example of this type of approach. All the required electronics for controlling the motor are on a single PCB. The input from the mains power can come from 90 or 250 VAC
at 50 or 60 Hz and a simple connection to a universal motor is provided as the output.
Figure 2: STMicroelectronics Universal Motor Control Demonstration Board.
An 8-bit MCU, the STM8S103F2P6
, controls the board and manages the motor control algorithm. Other STMicroelectronics devices are included on the board, in keeping with the dedicated platform strategy of using associated components, and these include the VIPer16LN
power converter, the T1235H-6I
TRIAC, and the L7905CP
linear regulator. The board documentation also includes the detailed layout (Gerber files) and a variety of test routines and results for key motor control features such as soft start, low-power-level operation, high-power operation, zero-voltage switching, and EMC test results. The small form-factor of the design can easily be used as a starting point for a production product, a goal of most dedicated platform approaches.
The above-described universal motor control demonstration board can be easily used to prototype a small motor control system such as those found in food processors, coffee grinders/brewers, or other small appliances. The much smaller form-factor, when compared to the much larger modular development platforms, makes it possible to create a prototype that approximates the size of the final product. By implementing a simple user interface via the on-board MCU, along with the various motor control algorithms, it is possible to quickly create a system prototype. This could be used for focus group or individual customer testing. When feedback can be provided via actual customer use experiences, it is possible to find functional issues that might not crop up in lab tests. Additionally, feedback from customers can provide valuable insight into the expected product use models. Often new or different uses are desired by customers, and this can open up entirely new market segments or applications. This is invaluable information only available when a working system is used.
Dedicated platforms with a twist
You will sometimes find that the dedicated approach is not used without some configurability. Take the Microchip
PIC32 Bluetooth Audio Development Kit
(Figure 3) with Microchip’s PIC32MX250F128B-I/ML-ND
. The main board has the resources needed for many applications, but there are also two daughter board locations, seen on the left side of the board, that can be used for added functionality. Shown in the figure are the Bluetooth HCI Radio Module Daughter Board and the 24-bit Stereo DAC Line-out/Headphone Amplifier Daughter Board.
Figure 3: Microchip PIC32 Bluetooth Audio Development Kit.
The availability of the two additional daughter boards makes it possible to address more applications and means that as new companion devices become available, perhaps supporting different standards, the baseboard need not be redesigned for each new companion device. This concession to some modularity of design is not unusual when standards are still in flux or when a few popular implementation options need to be supported.
The above development kit comes with a full-featured demonstration program, as well as software routines that can be used to customize a specific implementation. The software contains a full code suite that includes support for the Serial Port profile, Service Discovery Application profile, Advanced Audio Distribution profile, A/V Remote Control profile, and an AAC Decode Library, along with the associated protocols and controller interfaces. The code suite documentation shows the amount of flash memory and SRAM needed for the demonstration design.
The kit also comes with a significant amount of test routines and published results. Test results are given for a wide range of measurements for the total harmonic distortion for a 1 kHz frame of an uncompressed ideal tone sent over the I2S port with and without the Bluetooth stack or the audio DAC. These types of system measurements are particularly helpful with many applications where test development can be even more time consuming than application development.
An illustrative example design using the Bluetooth Audio kit is an audio-streaming controller with digital audio-processing capabilities. The controller can stream content over the Bluetooth connection and play it live and/or store it, as an MP3 file, in an attached USB flash drive. A touchscreen LCD display serves as the graphic user interface (GUI) to select the various menu items. The output jack can connect to a speaker, headphone, or the line-in connection of an audio system. The PIC32MX family device has a dedicated Multiply/Divide unit with a separate pipeline for multiply and divide operations. This makes it very efficient for executing digital audio processing functions to add advanced equalization and room-effect features. Advanced audio features, in particular, can benefit from significant customer feedback since they can be very subjective and difficult to quantify in a lab-only test setting. Note that with the kit- included software covering all the peripherals, file management, and standard audio coding functions, the design can focus on the value-added audio processing functions as the key differentiator and focus for the code development effort.
In addition to customer testing on the audio functions, customer testing can also be done on the GUI planned for the final product. This can help get customer feedback on GUI operation and uncover any misleading or difficult-to-understand commands or processes. An easy-to-use and intuitive GUI is perhaps just as difficult to evaluate objectively in a test lab as the audio features. A customer trial in a typical setting can provide much more information and is only possible if the target platform does not detract from the customer’s experience during testing. The more modular platforms can be difficult to use to obtain this type of detailed feedback due to their bulkier form-factors.
A system design example
One of the more powerful uses for the newest generation of full-featured development platforms is to create a complete working system as a proof of concept or prototype. Field trials, perhaps in challenging environments, are a common use for system prototypes. A typical implementation might use multiple boards, each optimized for a portion of the overall system. An example of such a working system was created by Digi-Key engineers using the Texas Instruments MSP430 Launchpad
modular development kit as a key element. It was combined with the CC430 Low-Power Wireless
Development Kit to create a wireless remote model rocket launch controller with streaming video support. These kits are shown in Figures 4 and 5.
Figure 4: TI MSP430 Launchpad Evaluation Kit.
Figure 5: TI CC430 Low-Power Evaluation Kit.
In the system implementation, the CC430 wireless kit is positioned next to the model rocket and controls the current to the rocket ignition system via an optically-isolated MOSFET. A similar kit positioned many meters away from the model rocket is connected to an Internet-connected laptop. The laptop can be logged into remotely and can send characters, via hyper-terminal and a wired serial link, to the CC430 wireless kit. Data is sent wirelessly between the two CC430 kits. The laptop-connected kit controls a servo supporting a smartphone used to remotely position and stream live video back to Digi-Key headquarters where launch control is located.
At launch control, a TI MSP430 Launchpad with a cap-touch booster pack
is used to create the user interface. The user interface hardware is connected via a wired serial port to a laptop that is connected via the Internet to the laptop at the remote launch location. The user can, via the touch sensor, move the remote control servo so the smartphone camera can scan the launch site to make sure it is safe to launch the rocket. Once all is clear, the touchpad can be used to send the command to launch the rocket. A video showing the system and its operation is available in the Digi-Key video library
Since they are powerful system elements, when MCUs are combined with full-featured development kits and associated reference designs, they can be used to develop systems in record time. Suppliers take different strategic approaches in creating these development platforms, and by understanding the advantages and disadvantages of each approach, you can make a better selection of the appropriate platform for your design requirements.
For more information on the MCU development kits and other parts discussed here, use the links provided to access product pages on the Digi-Key website.