Nowadays, “smart” gadgets, systems, buildings, and even appliances surround and improve our lives. Yet good judgment requires a brain. And an embedded system is inevitably the brain of smart gadgets.
Electronics, especially PCBAs that include microcontrollers on board are called embedded systems. Unlike your PC, laptop, or tablet computer, a microcontroller is often ideal for a single purpose rather than being organized to execute software. Hence, a thorough grasp of microcontrollers’ characteristics is necessary to develop embedded systems properly.
What Purposes Do Microcontrollers Serve?
Interestingly, the term “microprocessing” was formerly often used to describe embedded systems architecture. A microprocessor (MPU), a central processing unit with extra capability that cooperates with other chips to complete the onboard computer, or a microcontroller (MCU). Here, all computing components are on the same chip or IC, can be used as the central processing unit.
A new name was necessary due to the rising popularity of circuit boards, electronics, and systems using these ICs. Furthermore, even if microcontroller technology is improving, the fundamental components—memory, a clock or timer, a CPU, and I/O—remain similar to those of a PC.
ROM (EPROM, EEPROM) with executables preloaded to carry out particular functions is frequently part of microcontrollers. Nevertheless, flash or erasable memory is increasingly helpful since it enables off-board and in-circuit programming/debugging. It provides the bus with external data and power TX/RX capabilities.
Key Microcontroller Features
The properties of the parts help solid design choose the most suitable microcontroller for your particular needs out of the many varieties available.
Central Processing Unit (CPU)
The CPU does the math, keeps track of data, and sends control signals based on the programmer’s writing. The designer can’t see all the complicated wiring required to make the CPU work. Nowadays, with software like C, writing code for microcontrollers is usually pretty easy.
Memory
Flash memory is like a permanent notebook for a microcontroller, holding all the instructions it needs to do its job. RAM is like a scratchpad for short-term notes, but those notes get wiped away when the power’s cut. And the CPU’s internal registers are like its own little notebook for jotting down notes it needs to keep track of.
Support Circuitry
Because their main job is not to operate, monitor, or connect with external components, the many functional blocks that microcontrollers integrate cannot be categorized as peripherals. Yet, they are crucial since they facilitate the device’s internal functionality, streamline implementation, and advance the development process.
Debug circuitry enables the programmer to see the microcontroller as it executes commands closely. This is a crucial—and occasionally required—method of finding faults and improving firmware performance.
A very useful feature of microcontroller operation is interrupts. The CPU responds to interrupts by quickly executing a specified set of instructions in response to external or internal hardware-based events.
C-coded microcontroller programs fall into functions. First, a program’s execution is “vectored” by an interrupt to an interrupt service routine (ISR). Then, once the ISR has finished, the processor returns to the function running when the interrupt occurs.
The primary function of a microcontroller’s internal oscillator is frequently to generate a clock signal for the CPU and peripherals. A clock-generation module might be a peripheral if designed to provide signals utilized outside the device. Although internal oscillators usually have low accuracy, they are a useful and effective way to streamline the design and reduce board space in applications that accept this low precision.
Several kinds of power-supply circuits can be part of microcontrollers. For example, supervisor modules can put the processor in a stable reset state when the supply voltage is insufficient to support dependable operation. In addition, integrated voltage regulators enable on-chip generation of the necessary supply voltages. As a result, the device’s current inactive consumption can greatly decrease using power-management components.
Real-Time Clock (RTC)
Even when the system is off, real-time clocks (RTCs) built into microcontrollers may maintain track of the time and date. The RTC is a battery-operated clock that may be helpful for scheduling, alarms, and time stamping.
What Microcontroller to Choose for Your Application and How to Select It
Knowing the device you’ll use is necessary before designing an MCU-based product. However, suppose you don’t already have extensive knowledge in this area. In that case, it’s a good idea to focus on one device and branch out after gaining some solid experience. The skills and techniques in designing microcontroller-based systems are undoubtedly not specific to one part number or manufacturer.
Evaluation Hardware
A thoughtfully constructed, reasonably priced development board may benefit everyone, from amateurs to experienced engineers. Moreover, this is often the easiest and most reliable approach to assessing a microcontroller and becoming acquainted with its functional specifications and programming interface. Therefore, look for a reasonable cost evaluation board once you’ve reduced your search to a few potential part numbers.
Cost and Package Size
As their significance varies widely from one application to another, including these criteria in a particular step of the part-selection process is challenging. For example, when designing prototypes or systems that will never come in large quantities, engineers may have enough board space and be able to ignore package size considerations fully.
On the other hand, most electronic items must be either extremely tiny and affordable or very small or both. Therefore, you must always know pricing and package size while filtering out parts based on your essential criteria and favorite manufacturers.
Critical Parameters
Choose the most critical and specific criteria for choosing a microcontroller. They include internal oscillators, clock rates over 10 MHz, enough Flash and RAM, general-purpose timers, or built-in debugging modules. DACs are less frequent than analog-to-analog converters, which are more popular. Devices that support high processor frequencies should have priority if an ADC with an abnormally high resolution or sampling rate is necessary. For example, the C8051F060 from Silicon Labs includes two integrated ADCs. They can convert 16-bit data at one million samples per second.
Data transfer between an embedded device and a Computer requires the use of the USB interface. High-performance 32-bit MCUs from STMicroelectronics and Microchip run at 120 MHz. On the other hand, Silicon Labs provides two 8-bit families that operate at 100 MHz. Pay attention to microcontrollers with a USB module if you’re seeking a simple, portable way to add a USB connection to your system. In addition, it is advantageous to have a microcontroller especially designed to accommodate capacitive touch sensing, an increasingly common user interface. Prioritize this functionality while choosing parts since capacitive touch sensors are still uncommon in microcontrollers.
Choosing a Manufacturer
There are a lot of semiconductor firms that provide microcontrollers for sale. Nonetheless, it would be best if you began with a producer giving their microcontroller category much attention. As a result, you will have full access to a wealth of valuable design materials, such as app notes, example code, a top-notch integrated development environment (IDE), practical programming tools, and so on.
Additionally, you can more easily fine-tune your element selection based on each application’s requirements when working with manufacturers with larger MCUs. You can select a new part number without going through the significant changes brought on by switching from one manufacturer to another.
