Electronic Circuit Design With Think Radio
Think Radio is able to undertake circuit design across a wide variety of areas (medical applications, research tools, architectural, entertainment and live event sector, even children’s toys!), however Think Radio specialises in the Internet of Things (IoT).
What is the Internet of Things (IoT)?
The definition tends to be somewhat fluid, but usually an IoT device is considered to be almost anything other than a computer/tablet/phone that interacts with it’s environment (e.g. sensor, actuator) and communicates with other devices as part of that function. Is it gadget? Does it have some sort of communication ability? Then it might be considered an IoT device.
What is a microcontroller?
We have all heard of microprocessors. A microcontroller is a microprocessor with both memory (non-volatile flash memory and RAM) and commonly used peripherals all built into the same chip. These are things like the Serial Peripheral Interface (SPI), Inter Integrated Circuit (I2C, but also known as 2 Wire Interface), and, in the case of Nordic Semiconductor chips, a very capable radio.
At the heart of all but the simplest devices is some form of microprocessor capable of running code developed on a computer, compiled and then downloaded to the target device (a cross-compiler).
A large proportion of those devices use ARM processors, to maximise computing-power per unit energy (MIPS per mW), and maximise computing-power per unit cost (MIPS per $). A microcontroller contains both the microprocessor and other electronics commonly needed in such devices, and very often represent the best value for money solution.
If your device also requires radio communications (and perhaps even if it does not), then the Nordic Semiconductor range of microcontrollers are the head-and-shoulders market leader. Not only in value and performance terms, but also (in sharp contrast to their competitors) they have built industry-leading customer support, which, for smaller companies, really can be the difference between success and failure.
For these reasons Think Radio favours Nordic Semiconductor based development, and can pass on the considerable cost-savings of a very well-supported and reliable environment to customers.
Starting with one of the simplest, LED’s. Basic LED’s have become so inexpensive there’s almost no reason not to fit them to products. Higher performance LED’s offer an amazing range of capabilities, from ‘long throw’ devices designed for road signage, through to the photographic ‘flash bulbs’ used on phones. Multicolour Red/Green/Blue (RGB) LED’s are widely used, which can produce almost any colour by varying the proportions of each of the primary colours (for some shades of white, particularly ‘cool’ whites, a dedicated white LED is better).
Higher performance LED’s may require some attention to designing cooling (heatsinks), power supplies, battery conservation, and recharging (be careful selecting these, it’s a very competitive market, and some manufacturers are not above representing their devices as rather more capable than they actually are).
USB still very much has its place, in spite of the ascendancy of wireless devices. A product with a serial interface and an FTDI chip is still the ubiquitous solution that can be relied upon to work with any modern Windows PC, Apple Mac (or Linux), with no need to install new software (also see the section on Bootloaders for why USB interfaces are still important).
What are GPIO, SPI, I2C/TWI, PWM, ADC’s and DAC’s etc?
So we have a microcontroller, we have radio (or USB) communication to the outside world, but for our device to do something useful it needs sensors and transducers to interact with the world immediately around it.
The simplest form of interaction is buttons, and for that we have General Purpose Input/Output (GPIO). Microcontrollers are often able to support 40 or more (and, if necessary, even more than that, by using ‘bus expanders’). Still, the fewer the buttons, the less likely the user is to press the wrong ones. There’s an argument for completely button free devices, if possible!
GPIO’s are also useful for simple single-colour LED’s, which can be directly connected. In extremis, a technique called “bit bashing” can be used to make a software equivalent of other interfaces from spare GPIO, if the desired interface is unavailable.
More sophisticated peripherals, such as LCD screens, that need to quickly shift large amounts of data from (or to) to the microcontroller often make use of the Serial Peripheral Interface (SPI). Bit rates of up to 8MHz enable screens to be updated with no visible lag, which tends to be very important for games.
Another widely used interface is Inter-Integrated Circuit (I2C), also known as the ‘Two Wire Interface’ (TWI) offers reliable simplicity, and ease of use, at lower data rates. Many, many manufacturers offer peripherals with I2C interfaces, or SPI, or both.
To control electric motors Pulse Width Modulation (PWM) is also in widespread use. PWM also has huge application in precisely controlling the colour and brightness of RGB LED’s.
ADC / DAC
Finally Analog to Digital Converters (ADC’s) and Digital to Analog Converters (DAC’s) are widely used to interface with microphones and speakers respectively (and a whole host of other analog devices such as temperature sensing, light level sensing etc.).
What is important? In most cases, it’s responsiveness. Bright screens, rich colour and high resolution are all possible, and look very good in photography, but in the user’s hands the device must respond instantly, and that demands excellent design.
A poor choice of screen (or a lack of firmware sophistication) may also result in significant power consumption, which may then entail larger batteries, or user-frustration from short battery life. Well thought out display support very much defines the ‘character’ of the device, and consequently user satisfaction.
Accelerometers, in good design, can be quite magical, waking the device the moment it is touched, detecting device orientation, and even in warranty claims so that any history of severe impacts can be recorded. Accelerometers are so inexpensive that, in may cases, it’s worth designing in support to facilitate second-generation products.
Hall effect devices detect magnetism, and make for delightful interactions such as opening a snap-case also powering-on the device (Hall effect devices also make perfect never-wear-out switches, hence their use in flight-critical systems in aviation).
Touch sensors may also be a great solution. For all but the most trivial applications they involve quite a bit of engineering effort, and ideally specific support chips.