In the early days of Internet of Things devices, we set out to design a custom solution for one of our customers. Though the customer cannot be revealed, the Internet of Things Platform we designed is a solution which support the end use and can be scaled when necessary. The Internet of Things Sensors on board measure a multitude of activity and report back on a schedule. At the time of the original design, a Single Board, Off The Shelf Solution was not available driving this One-Off Hardware and Software Solution.
Core Blocks of this Design
Microchip Low Power, High Performance PIC18F46J50 MCU: this MCU is the workhorse of the design. Here is the datasheet if interested. The types of I/O port configurations used in this design include:
- RS-232 Comm Port UART I/O
- UART Control to WI-FI Module
- LED Status drivers
- Input Switch status
- Thermocouple A/D
This MCU is programmed to wake for a few milliseconds each hour and perform a specific task. The battery on board is able to stay charged for 4+ months.
To insure an Internet of Things Platform that would be supported in the future, the Digi-International WI/FI Xbee module was selected. This module is easily configured and is very robust. It even has extra I/O and A/D which can be accessed directly if needed. Here is the datasheet if interested.
The Core Internet of Things Sensors piece to this design is a thermocouple and an internal to the MCU a temperature sensor. The thermocouple has a discrete circuit around it to minimize noise as well.
The embedded software running on this Internet of Things Platform is written in C and compiled using Microchip’s toolset. Loading of the software is through Microchip tools as well. The core functionality of this software is to wakeup on either an event or on a preset time, read inputs, make decisions on the readings, set different outputs based on the readings and then push all data to the cloud prior to going back to sleep.
Internet of Things Monitoring Software this software, at the time of the design release, was Etherios. From a cloud based service, each sensor can be queried for sensor readings. Also, the data-set is such that custom database work can done if desired.
Here is an image of the final circuit board before population, during a test fit of the enclosure. Custom Metal Enclosures were designed by Rigid Concepts. Customer branding and final configurations not shown.