When integrating a Raspberry Pi into a product or project, the A+ maybe an ideal choice thanks to its reduced price and size. What applications can the Pi A+ be applied to and how does the A+ compare to other models such as the B range?
The Raspberry Pi A+
The Raspberry Pi A+ computers come in two types (the +1 and the +3), which are both cut-down versions of the standard Raspberry Pi range (such as the Model B). By sacrificing RAM, processor power and I/O peripherals, they are $10 cheaper than their counterparts, physically smaller, consume less power and can provide an extremely robust microcontroller platform when compared to other microcontrollers such as PICs and Arduinos.
Image: Raspberry Pi A+
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For example, the Model A 1+ computer has only one USB port, no networking capabilities, 512 MB of RAM and a single 32-bit Arm core. The Model B 3+, on the other hand, has four USB ports, Wi-Fi, Ethernet, 1 GB of RAM and four 64-bit 1.4-GHz Arm cores. While the Model A range of computers may be less capable of typical desktop computing (such as word processing and online streaming), they are incredibly useful in scenarios in which complex tasks need to be performed with access to external circuitry via the GPIO and USB. The Model B 3+, meanwhile, is a more powerful and capable system, it carries plenty of additional hardware that may be unnecessary in a final product containing a Pi, and this extra hardware sees an increase in power consumption, weight, physical dimension and price. Therefore, the Model A 1+ and 3+ can be thought of as finalized, field-ready platforms that are used after prototyping with a Model B 3+ that has been developed on a test bench that requires a user to interface with an OS via a mouse, keyboard and display.
Use as a microcontroller
Unless an application requires high-speed GPIO access (such as a signal processor, logic analyzer or bus interface), then the Raspberry Pi A+ has some serious advantages over typical mainstream microcontrollers. To start, the A+ Pi has a 32-bit Arm core clocked at 700 MHz whereas typical microcontrollers such as the Arduino and PIC operate at speeds in the sub-100-MHz range. This huge increase in processing speed along with considerably larger RAM sizes (512 MB in the A+ compared to 16 KB of RAM on a standard micro), allows for operating systems to run alongside user applications and handle complex tasks such as file systems, network access and multi-threaded applications.
But the advantages of an operating system go beyond OS functions; more abstract languages that are easier to program in can be used. One feature typically not seen on microcontrollers is object-oriented programming due to memory structure and size, but a Raspberry Pi A+ being used as a microcontroller can be programmed in languages such as C++, Java and Python, which allows for incredibly complex programs. The use of high-level languages such as Python and Java also significantly reduce time to prototype as such languages often provide many libraries to perform complex functions such as file interactions, socket programming for network communication and even USB interfacing.
While the Model B 3+ is capable of operating as a microcontroller, its increased size with the additional hardware may provide no benefit to the end product. The processing power of the Model B 3+ is also considerably greater than the A+, but if the A+ is perfectly capable of running an end application, then the additional processing power of the Model B 3+ will not only be unneeded but will also increase the power consumption of the product as well as the cost.
Portable applications
Some of the biggest challenges with portable applications (drones, robotics, et al) often involve weight, physical size and power availability. Therefore, if a Raspberry Pi is needed in such an application, then the Model A 1+ would be the optimum choice as it consumes the least amount of energy, is the smallest in dimensions and is the lightest. While the compute modules are lower-power and far lighter, they are also not easy to prototype with and require special boards to interface with, making them prototype-unfriendly.
The Model B 3+, as a comparison, would provide improved processing capabilities, but its larger physical size, nearly double weight (45 g compare to the A 1+ 23 g), and almost 5× higher energy consumption (5.661 W compared to the A 1+ 1-W power consumption) would see it quickly unusable in applications requiring the use of batteries that are also required for motion.
Remote applications
Being able to power the Pi with main electricity is fine, but when the only power source is a solar panel with a battery backup or some other unreliable energy source, then keeping energy consumption at a minimum is paramount. Those same locations that do not provide plentiful amounts of electricity may also have limited connectivity with no access to Ethernet connections to a router or be mounted in a location that is too difficult to obtain physical access to. These applications (such as rural monitoring stations and weather monitoring on sea buoys) could benefit from the Raspberry Pi Model A 1+ with its small size and low power consumption of just 1 W whereas other systems such as the Model B 3+ can consume in an excess of 3 W just in standby mode (before any data processing is done). However, while the Model A 1+ is easy to mount and consumes little power, it has no networking capabilities, which may see the need for a small USB Wi-Fi dongle to allow for remote access (this addition of a Wi-Fi dongle will impact the energy consumption, which could be higher than the Model B 3+). Therefore, if the Model A 1+ is being used in a remote location, then the power consumption of any Wi-Fi adaptor should be determined; otherwise, the Model B 3+ could be beneficial with its built-in Wi-Fi.
Visual processor
While the Model A 1+ is a reduced Raspberry Pi, it still has video-processing capabilities with an HDMI output and camera input. The ability to process image data from a USB webcam or other camera device immediately opens opportunities for the A 1+ to be used in scenarios that require image processing such as drones, robotics and security systems. If combined with high-level programming languages with premade libraries (such as Python and OpenCV), a Pi can easily be made to process neural networks that can recognize objects, provide object avoidance and facial recognition that can be off-grid. This form of processing (also known as edge computing) removes the need for the Pi to be connected to some cloud service to process data and, therefore, provides a lower latency between camera input and resulting output. A drone, for example, could incorporate a Model A 1+ as a visual processor for object avoidance and path finding, all while having a reduced size, weight and power consumption when compared to other Pi computers.
Use as a controller
While the Raspberry Pi Model A 1+ has potential application as a microcontroller, it also has a very real possible application in controller scenarios, which could include graphic terminals, motor control in machinery and home automation. Despite being physically smaller than other Pi computers, the Model A 1+ still has the same standard 40-pin GPIO, which gives it plenty of access to potential signal sources such as limit switches, motor stepping control, alarm signals and other microcontrollers via SPI and I2C. This I/O access can easily be expanded with the use of the single USB port if connected to another external microcontroller, which could offload critical I/O operations from the Pi.
The Model B 3+, by comparison, offers integrated Wi-Fi and additional USB ports, which may make it the better choice in terminal applications, but in scenarios that don’t involve human interfaces such as keyboards and displays, there may be a cost benefit to choosing the Model A 1+.
Image: Raspberry Pi model comparison chart
