Connecting a small display to the NavQPlus to show information such as IP address and link status.
Introduction
This tutorial demonstrates how to write text on SSD1306 OLED display modules using the I2C interface of NavQPlus board.
Items needed
S. No.
Name
Quantity
Hardware procedure
You will need to create a custom cable to connect the OLED 4 pin signals to a JST-GH 6 pin connector to plug into the NavQPlus.
NOTE: An off the shelf cable is not provided, but it is simple to make your own according to the table below.
Connections from SSD1306 OLED to J12 Port on NavQPlus
OLED pin header #
Name
JST-GH 6 Pin number of J12 on NavQPlus
Software procedure
Overview
In this example software, a daemon service polls the desired network interface every one second for its link status and IP address and publishes the same on an OLED display.
Any of the standard network interfaces may be specified when starting the daemon.
Prerequisites
If not already running the standard NavQPlus Ubuntu POC image, then flash the following image on the micro SDcard of NavQPlus: or greater. Click on the desired image and download the "wic.bz2" file. Extract it and flash the resultant ".wic" image on the micro SDcard. More detailed instructions are .
NavQPlus board setup
Install python libraries
On the NavQPlus board, install the python packages and . They are required as prerequisites by our application. They are a driver for the OLED and also a small python imaging library.
Perform the following steps to clone the project and set-up the application.
Review the python code directly in the Git repo here:
Create Daemon
Create a daemon service that will invoke our application in the background, by running the following steps. The command "systemctl start" starts a new instance of the application in the background,, "systemctl status" returns the running status and latest logs of the said instance of the application and "systemctl stop" terminates the said instance of the daemon service.
Rememeber, in order to access the service using "systemctl status" and "systemctl stop" commands, the parameters must be the same as the ones used to start the service. (using "systemctl start").
Otherwise a different instance (the one corresponding to the passed parameters) of the service will be accessed.
In the provided example python code, it does include a check whereby if the Daemon attempts to write to a non existent OLED, then the write command will fail and the daemon will stop itself automatically.
Example 1: 128x32 OLED display
Use the command below to track the "usb0" interface and the resolution of your OLED module is 128×32.
This is the OLED display shown below in the image
Example 2: 128x64 OLED display
Use the command below to track the "usb0" interface and the resolution of your OLED module is 128×64.
This is the OLED display shown below in the image
Stopping the interface
To change interface name, display width and/or display height, or stop the service, run the following "systemctl stop" command,
you may then restart the service using "systemctl start" command using new parameters.
This is relevant to when you want to track a different network interface, or if you want to use an OLED module that has a different resolution than the one you were using before.
Demonstration with Videos
Displaying network and system status
Our application prints the link status and ip address of the specified network every one second on the SSD1306 OLED display. To change the link status of the network interface to UP or DOWN, you may use the following ifconfig commands. Note: when the link status is DOWN, the ip address is shown as NULL.
If the text is not displayed on the OLED screen, please retry after 5-10 seconds.
(YouTube)
Displaying GIF and PNG files
Animations and images could be displayed on the SSD1306 OLED module using the companion repository. Kindly refer the following demonstration video for the same.
In our demonstration we only tested with displaying GIF and PNG files.
