An integrated and compact Wi-Fi-enabled display module can be used to display and process data from the cloud.
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.
1. This Internet of Displays module incorporates Wi-Fi support.
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.
A more integrated and straightforward approach to graphics-based application development is possible with the Workshop4 environment, which can be downloaded for free from 4D Systems’ website. A 10-pin FPC cable connects the 4D IoD to a 4D gen4 IoD programmer (Fig. 2). The programmer provides all connectivity to the module and the means to power, program, and test the IoD module.
2. A programmer board provides debugging and configuration support without having to incorporate it on the module.
The ESP8266 is a wireless microcontroller that’s widely supported within the Arduino community. As a result, you will find a plethora of open-source projects that leverage the use of its Wi-Fi capabilities, and connect to free data sources such as Weather Underground.
Applying the Module
The 4D IoD series is suitable for a range of Internet of Things (IoT) applications. Consider, for example, an application that connects over Wi-Fi to a data source—Weather Underground—in order to display the current temperature and humidity for a specific location.
Pulling together this application involves three main tasks: designing the way the weather information is presented graphically; using an API to gather data from Weather Underground; and displaying the information.
Prerequisites to starting this project include downloading and installing the Arduino IDE, and installing the ESP8266 community board manager files, the GFX4d library, and the Workshop4 IDE. Full instructions and necessary files are provided in the gen4 IoD datasheet and on 4D Systems’ GitHub page.
3. The Workshop4 IDE can display code (left) and a simulated display (right).
First, let’s tackle the GUI using Workshop4. Having downloaded and installed the latest version, you need to open up a new project and select the gen4 IoD display from the list of available displays. You will see two main window frames
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