The Tower - and Other - Development Platforms Provide Application and MCU Flexibility

Development and evaluation boards and kits are an important part of the design engineer's toolbox, and such products are doubly important in the microcontroller (MCU) space as a way to learn about new processor architectures and jumpstart development. While most boards and kits are based on a specific MCU and often target a specific application such as motor control, Freescale's Tower system allows a designer to experiment with different MCUs and applications. Indeed, the platform can be used to develop touch-based applications, motor-control systems, robotics, and many others. Let's examine the purpose of development kits in general, the Tower concept, and some of the Tower products that allow both MCU and application flexibility.

Before we dive into the details on the Tower system, let's consider the broad landscape of development products, because there is no single correct answer as to how to develop and supply such a tool. Some kits are developed specifically to hit a very low price point. For example, STMicroelectronics just introduced its latest kit, the STM32F4 Discovery Kit, so that virtually anyone can afford one. The kit is based on the STM32F407VGT6 MCU that integrates an ARM Cortex-M4 core. The kit includes MEMS-based motion sensors and peripherals that come in handy for audio applications.

Texas Instruments (TI) offers a good example of an application-specific kit in its Evalbot robotics kit. The kit is based on an ARM Cortex-M3 MCU and includes some small motors and operates from battery power. There are several versions of the kit based on a different set of third-party software-development tools included in the kit.

Now let's move on to the Tower concept. The mechanical basis of the Tower System is formed by two PCBs that Freescale calls Elevator modules (Figure 1). The Elevator modules form the walls of a modular system and as many as four MCU, microprocessor, or peripheral modules mount between the walls. The Elevator modules handle power and ground distribution and host PCI connectors into which the MCU and peripheral modules are inserted. One of the Elevator walls is called the Dummy Elevator as it only provides ground connections and mechanical stability. The Functional Elevator distributes power and connects the four modular slots.

Figure 1: The Tower system can connect MCU-based controller modules and peripheral boards between two elevator modules.

Ultimately, the Tower System will allow development teams to quickly configure and evaluate systems based on 8-, 16-, and 32-bit MCUs, microprocessors, and digital signal controllers (DSCs). And in some cases, teams may choose to deploy the Tower-based designs in low- to-moderate volume applications.

DigiKey stocks more than fifty Tower products that range from multi-board starter kits to application-specific boards and MCU-specific modules.

S08 and RS08 MCUs

Let's have a more detailed look at the Tower technology from the ground up to fully explore the flexibility in the system. The recently introduced TWR-S08UNIV controller module (Figure 2) is a good place to start. In Tower parlance, a controller module is a microprocessor- or MCU-based board that could be the heart of a modular Tower system or that can be utilized as a standalone development board.

Figure 2: The TWR-S08UNIV controller module can host a variety of S08 and RS08 MCU mezzanine modules and can be used as a standalone development board or in a Tower system.

The TWR-S08UNIV board includes a daughter card socket for an MCU module. The board is designed to allow you to work with either the S08 or RS08 MCU families. The 8-bit S08 family targets low-power applications and the RS08 subset includes low-pin-count MCUs with less than 16 kbytes of memory. There are numerous S08 and RS08 daughter cards available such as the TWR-S08DC-QG8-ND that is based on an S08QG MCU that targets battery-powered devices. Alternatively you can buy the TWR-S08UNIV-DEMO-ND kit that includes the controller board, five S08 MCU modules, and one RS08 module.

Both the board and demo kit include software to accelerate the development process. For example, the S08 and RS08 MCUs include peripherals such as A/D converters and a Timer/PWM Module (TPM). Freescale includes sample code for both.

To expand the capabilities of the base board, two options are available: using the elevator boards so that you can add peripheral boards in a modular fashion and/or adding mezzanine modules via Tower Plug In (TWRPI) connectors. The S08 board includes five TWRPI connectors including two that can be used to add sensor modules. For example, the TWRPI-MMA6900-ND module implements a two-axis accelerometer while the TWR-SENSOR-PAK-ND sensor kit includes an accelerometer, and pressure and touch sensors.

Expansion capabilities

To build up a modular multi-board Tower system based on the S08 controller board, you will need the TWR-ELEV-ND elevator board package that includes both the Dummy and Functional Elevator boards. There are a broad set of peripheral boards that can be added to such systems including the TWR-LCD-ND LCD display board. There are peripheral boards that are specific to many applications such as motor control, wireless mesh networking, and even an electrocardiograph board.

“Flexible” is a good word to describe the Tower system. The mezzanine modules and peripheral boards mentioned here can be used across a broad selection of controller boards that cover Freescale's entire MCU portfolio. In some cases, full-fledged development kits may provide the best entry point to using Tower technology.

For example, near the top end of the Freescale portfolio you will find the Kinetis family, based on the ARM Cortex-M4 processor core. The TWR-K53N512-KIT kit includes a controller module based on an MCU from the K50 family announced this past summer with a specific target of medical applications. The kit includes the elevator boards and required cables.

Freescale even has a complete kit targeted at robotics. The FSLBOT-ND kit includes all of the components and boards needed to build a small walking robot (Figure 3). The kit includes a controller module based on the MCF52259 Coldfire MCU along with four servo motors and all of the mechanical parts needed for the robot.

Figure 3: The FSLBOT kit includes everything needed to construct a walking robot using components of the Tower system.

In summary, the Tower system is unique in its ability to support development in many different application areas and to allow design team swap between different MCU and microprocessor families while using the same peripheral functionality. You can easily compare the capabilities of different architectures in the same application. Moreover, you can reuse the peripheral functions that you invest in on future projects. Freescale also supplies schematics of its controller modules allowing you to transfer your work easily when moving from prototype to production. And finally, Freescale has opened the Tower system to other processor and hardware manufacturers.