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Controllers, processors, and the right tool for the job

There are so many small single board computers and prototyping systems available these days that it gets confusing trying to figure out the differences. A first consideration is whether the basic hardware is a microcontroller or a microprocessor. Andrew Black discusses this in Arduino or Raspberry Pi? The Arduino is a prototyping system based on a microcontroller. That means it features pins for controlling switches and motors and conversion between analog and digital voltages. The Raspberry Pi is based on a microprocessor and its focus is towards external memory and devices such as keyboards and displays and networks.

“The Pi has a clear advantage for complex networked and high performance embedded applications, and those which involve driving a video display or USB peripherals. But when power consumption is of paramount importance the Arduino has the edge, as it will only consume microwatts when in sleep mode compared to the watts drawn by an idle Raspberry Pi running Linux. Due to the much simpler nature of a microcontroller-based approach the Arduino may also have an advantage over the Pi in applications which demand a very high degree of reliability.”

The Arduino, based on an ATmega, seems to be the most popular microcontroller prototyping system right now. Radio Shack even has them. Other options include the BASIC Stamp and the Revolution Picaxe based on the Pic microcontrollers.

The second and third considerations are cost and development facility. The Picaxe provides a contrast point on these issues as the startup costs can be very small compared to other options and the chip programming is facilitated by Revolution’s IDE (integrated development environment) and the firmware it installs in the chips it sells. See The true cost of a Raspberry Pi is more than you think for a rundown on the sorts of startup issues you can encounter that not only influence the monetary investment needed but also provide a barrier to actually getting started in terms of hassle and setup.

A key factor in choosing the right tool for the job is the trade-off between device power consumption and the mathematics and speed capabilities required. SBC’s (single board computers) often run at hundreds of MHz clock speeds, use 32 bit or larger native number sizes, have megabytes of memory storage and need power measured in watts. Microcontrollers usually run at just a few MHz with 8 bit number sizes and memory often measured in kilobytes and needs milliwatts of power so it can run off small batteries.

What will be interesting in this arena is when hacking surplus smartphones matures. There are a lot of these things that are at the disposable electronics level. They have decent processing capabilities and many sensors as well as display and input mechanisms. In other words, the can offer much more than a typical micro prototying board and be had for next to nothing. What is missing is the technique to hack them and the development environment to replace their firmware. That will only come from serious hacking effort re-engineering the equipment.

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