As microcontrollers become smaller and cheaper, the functionality of many external components is being integrated directly into the microcontroller. Eight-bit microcontrollers come in a variety of package sizes, random access memory (RAM) and read-only memory (ROM) sizes, serial communication buses, and analog inputs and outputs, enabling engineers to select a microcontroller that matches their design requirements and cost constraints. Some microcontrollers integrate the microcontroller and almost all related analog and digital peripheral circuits typically found in an embedded design, such as: analog to digital converter (ADC), digital to analog converter (DAC), pulse width modulation (PWM), amplifiers, timers, counters, universal asynchronous receiver-transmitter (UART), small computer serial interface (SCSI), SCSI parallel interface (SPI), intelligent interface controller (I²C), and USB. This mixed signal integration allows customers to significantly reduce the number of components they have to use, greatly improving system quality and reliability and drastically lowering bill of materials. With this continued integration of external components into the microcontroller it was only a matter of time before the integration of reliable radio technology and advanced mixed-signal array microcontrollers occurred. The result of this integration is the potential to unlock value (read profits for manufacturers and ease of use for end consumers) across a myriad of applications in the consumer world as shown in Figure 2.

The issue now is figuring out the right wireless technology and microcontroller to integrate together. If the right microcontroller is merged with the right radio the resulting technology will enable designers to significantly decrease development time, component count and system cost while improving operating range, power consumption and latency. Besides benefits to the design engineer, the integration also simplifies supply chain logistics by significantly reducing the numbers of components in the device.

So what is the impact on end applications? The biggest impact is in two areas: ease of use and installation costs. Integration leads to a lower learning cycle and complexity level of implementation. By going ‘wireless’ you are able to carve out huge costs of installation. For example, using a wireless solution to set up carbon dioxide detectors in an existing building enables installation in days and does not require any breaking down of walls or expensive wiring.

However, you have to be cautious and intelligent about choosing the right solution. Let's begin with the wireless technology. The first step is deciding what kind of system you are building: is the system a high-end consumer electronic (light control system in a house) or a low-end commodity ($12 wireless mouse)? This would help in deciding between a one-way wireless protocol and a two-way wireless protocol. You could move along the reliability spectrum of wireless technology as shown in Figure 3.

Finally, the wireless protocol should be as simple as possible to enable an easy learning curve and implementation in a reasonably sized code space. You should also be evaluating intelligent binding schemes and security algorithms. (You don't want your garage door opener to be a gateway into your PC at home.)

The next step is the microcontroller choice. The first thing is to find one that has integrated the wireless radio in it. Beyond that there are several factors to consider:

• Microcontroller scalability

  Preferably you want to choose a family that allows you to scale both up and down in terms of flash size, inputs and outputs (I/Os), and various analog and digital components. It would be wise to choose a mixed signal array in case you are also looking at temperature sensing and voltage sequencing in your application. (For example, temp sensing in a server farm could trigger fans for the servers and at the same time send a wireless signal to a hub to record data for analytics at a later stage. The analytics could help in energy conservation and optimize power payments.)

• Toolset integration

  The ideal scenario is to have the wireless radio be a user module/library that would simplify radio communications development in the design environment. The designer software development environment should be GUI based with simple point and click options. It should provide flexibility to code in either C or assembly language and use event triggers and multiple break points in debugging the design.

• Design time reduction

  A nice to have feature is a toolset with a higher level of abstraction, enabling design at a level not requiring C or assembly language. This enables designers to focus on application expertise and create a custom solution using a system similar to choosing from a catalog and linking the parts in a logical manner. There would be an additional bonus if the tool could create datasheets, schematics and bill of materials to reduce total design cycle time to hours instead of weeks or months. Some of this may not appeal to the ‘die-hard’ engineers who prefer to hand code assembly and debug it using logic analyzers, but most modern engineers welcome tools that will reduce design time and increase the reliability of their product.

It is clear from a business and technology perspective that the time for integrating reliable 2.4 GHz radios with flexible mixed signal array microcontrollers is here. The rest of this article will explore an application example of a garage door opener and describe some of the real world design issues faced in implementing this using an integrated solution such as PRoC from Cypress Semiconductor Corp. vs. a discrete multichip solution.

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