The number of IoT devices currently around the globe is constantly growing, with a current estimated number of internet enabled devices to be around 26 billion. Microcontrollers of the past did not typically (if at all) have internet capabilities due to the complexity of IP, the lack of internet infrastructure, and their cost to implement in designs. However, the constant falling cost of silicon and the improvements in microcontroller technology now regularly sees powerful CPU cores with large memories and many peripherals that can easily handle complex tasks while costing no more than a few dollars. Projects that would normally require large PCBs, heavy batteries, and expensive processors can now be made to fit on a piece of silicon no bigger than a grain of rice powered by a battery that would fit on a dime. One such example of this achievement of miniaturization would the SensorTile produced by ST.
The SensorTile is an incredibly small IoT device that incorporates a microcontroller, Bluetooth transceiver, and an array of sensors, all on one miniature PCB. The heart of the SensorTile is the STM32L476, which is a 32-bit ARM core that is clocked at 80MHz, 1MB of FLASH, and 128KB of SRAM. The SensorTile sensors include multiple accelerometers, gyroscopes, barometer, and microphone, while also having external connectors for multiple busses, including GPIO, SPI, I2S, USB, UART, PDM, and ADC.
The SensorTile module itself is incredibly small, measuring just 13.5mm x 13.5mm (which would typically be difficult to prototype). However, the SensorTile kit also includes a shield that the SensorTile can be inserted into, expanding the minute I/O contacts to 2.54mm pitch connectors. The shield also includes additional connectors and hardware, including an audio DAC, USB port, STM32 Nucleo, Arduino Uno R3, and SWD connector.
One of the biggest advantages of the SensorTile kit is that it can be programmed with the Digi-Key IoT Studio environment. This means that all the onboard sensors can be accessed with ease, using the tile-based software while mobile apps can interact with the SensorTile to perform almost any task imaginable. While the SensorTile itself does not have Wi-Fi capabilities, it can still be connected to the cloud via a Bluetooth link (with a Bluetooth-enabled smartphone acting as a bridge between the cloud and the device). While this may seem like a disadvantage to some makers, it does have some advantages, with one example being that the SensorTile can be powered by small Li-Ion batteries (such as the provided 100mAh battery).
The size of the SensorTile makes it a strong candidate for applications that have size and weight constraints, such as remote installation and drones. But one application where the SensorTile really excels is wearable technologies: the SensorTile can quickly prototype wearable projects such as sports watches and body monitors that can relay information about the wearer to a nearby Bluetooth enabled device.
For viewing a project based on using the sensor tile as a wearable platform, see this project post.
The SensorTile is an impressive feat of technology with a powerful microcontroller, integrated sensors, and connectivity, yet fitting onto a PCB smaller than a penny. But thanks to the Digi-Key IoT Studio, the SensorTile becomes an even more practical IoT prototyping platform for both makers and engineers who want to develop products for a rapidly growing industry.