As the IoT rapidly gains traction, there’s a clear need for internet-connected sensors that also have a simple display function. Such sensors will highly automate various functions by sending data to the controlling cloud application. Nonetheless, the ability to display information locally is becoming increasingly important in the way that local or field engineers can confirm updated data received from the cloud, or simply confirm that communication and operational functions are normal. This article highlights, using practical examples, a wireless internet-connected display module that achieves the above requirements utilizing a very straightforward, low-cost method.
For the majority of IoT deployments, sensors and actuators will operate wirelessly using either Wi-Fi or Bluetooth. While Wi-Fi is much more power-hungry than Bluetooth, especially the Bluetooth Low Energy profile (BLE), Wi-Fi does have the benefit of being able to communicate over greater distances with a high data-transfer rate. The topology of many IoT deployments includes gateway devices that provide two-way communication with the cloud and a means of batching data collected from Bluetooth-connected local sensors, in addition to some degree of local control function.
For the embedded developer, a number of compact embedded single-board computers feature have Wi-Fi connectivity. Adding a display to the mix can be achieved in a variety of ways, most often using a pre-assembled display module or creating a discrete design.
However, recent developments have seen the launch of a complete Wi-Fi-connected embedded platform that incorporates a touch-sensitive display. An example of such a platform is the gen4 Internet of Displays (IoD) series from 4D Systems. Based around an Expressif ESP8266 Wi-Fi microcontroller, the module offers resistive-touch, 320- × 240-pixel, TFT, 65,000 true-to-life color display sizes of 2.4, 2.8, or 3.2 inches (Fig. 1).
In addition to a micro SD socket for use in data-logging and image-file applications, the module has 512 kB of flash memory for user application code and 128 kB of SRAM, of which 80 kB is available for use. Measuring 78.4 x 44.8 x 7.2 mm (2.4-in. model), the modules can be easily programmed using the popular Arduino IDE. A GFX4d library enables the fast development of graphics-based applications through the use of primitive graphics functions—it’s available for download from 4D Systems’ GitHub page.