Developing a remote messaging panel based on e-paper technology
01 August 2021
Pervasive Displays_remote messaging
There are many potential use cases in which the ability to deliver simple one-way messages to remote displays is of real value, including home & building automation, digital healthcare & the hospitality sector. In such scenarios, as Alchin Wang, President of e-paper display (EPD) specialist, Pervasive Displays (PDi) explains here, e-paper has certain fundamental attributes that make it an optimal choice for rendering messages of this kind…
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So what might be some of the motivations for a remote display messaging system? Well, many Western economies have ageing populations, and finding ways to permit the elderly to continue to enjoy independent living currently presents a major challenge. Having a straightforward push messaging system would allow relatives or caregivers to send useful messages that provide support. These could be to prompt elderly people to take their medication, or remind them about other activities that they need to do that day. It would also provide a means via which to inform them of upcoming events that they need to be aware of (such as family member birthdays), and let them know when they are expecting a visitor or that they have a hospital appointment to attend.
This sort of solution can be very versatile, with scope for it to be applied to many other use cases. Within an office setting, remote messaging units could be placed on staff desks, providing details of scheduled meetings, showing relevant business news updates, or even regularly delivering motivational quotes. Likewise, wall-mounted versions could display information such as meeting room bookings, showing when the room is next available again. In restaurants, this technology could inform diners of specials for the day, and in hotel rooms, it could provide a subtle way to leave personalised welcoming notes to guests upon their arrival.
Constituent elements of the messaging system
The basic set-up of this system consists of two key elements. There is the remote unit with an e-ink display which receives and displays the messages. An internal clock is integrated into the hardware, so that the date and time is continuously updated. The second element is the cloud-based back-end, supporting the remote unit. This back-end receives the message data, then authenticates and timestamps it, before pushing it onto the remote unit using wireless communication.
Why use e-paper?
The fact that e-paper offers bi-stable operation is a real benefit to such a system. It means that the display only needs power when the image is initially being rendered. After that, it remains the same until a new message is actioned. Not only does this make e-paper technology highly-suited to remote, battery-powered applications, like the ones described
Pervasive Displays_EXT3 launchpad and bridging cable
herein, but it means that operation can continue even if the back-end is exposed to power outage. The remote unit would continue to show the current message, only changing this once power had been restored to the back-end. At that point, any delayed message could be sent out, with the remote unit subsequently comparing it with what was already stored on its non-volatile memory, before amending accordingly.
Other plus points of displays based on EPD technology include the superior readability they provide. The advanced units available from PDi offer high contrast output with 130DPI resolution. Furthermore, they exhibit strong resilience to the effects of direct sunlight. Black-white-red screens offer the additional red colour for prominent messages, with the red colour proving very eye-catching to draw attention to the messaging on the screen.
It should also be noted that e-paper is far less intrusive than other display types, another reason why it is more appropriate for applications of this kind, where the primary objective is to not have a negative impact on the user or the environment in which they are situated. Conventional displays that are constantly emitting light could be off-putting to the elderly, or to restaurant diners, hotel guests and office workers. In a similar way to it being preferable to read an e-book using a Kindle rather than a tablet, e-paper based display units won’t interfere with people’s day-to-day living. It’s just there in the background, for someone to look at when they choose.
Optimised hardware: EXT3 development kit
Using Pervasive Displays’ Extension Kit Gen.3 (EXT3) board and one of its e-paper display modules, accompanied by a host processor board with wireless connectivity, it’s easy to create a remote messaging unit. To keep the power budget to a minimum and given the relatively small data requirements involved, it’s recommended that Bluetooth Low Energy (BLE) technology is relied upon. Under such circumstances, the messaging unit will be able to run for a period of more than a year without the battery needing to be replaced. Another option is LoRa.
The EXT3 provides a highly effective platform for engineers to evaluate the parameters of their project. Using it, they can decide on what items need to be specified – which host microcontroller is going to be most appropriate, which of the EPDs available will be the best fit, what the memory demands will be, and so on. It’s supported by a series of open-source software libraries and application examples to provide engineers with a head-start on their projects. This will enable them to get through the early stages of development quicker and move on to creating working prototypes.
Pervasive Displays_E-paper display EXT3 board
As well as the necessary driver firmware, there is 1MByte flash memory embedded into each EXT3 board, plus slots for adding external memory reserves. It can be used in conjunction with a wide range of different items of processing/development hardware. These include products from the likes of Arduino, Raspberry Pi, Adafruit, and also Texas Instruments LaunchPad boards for fast prototyping. Connection to these boards can be achieved by attaching cabling to the EXT3’s 20-pin header.
PDi offers an extensive array of e-paper display module options. These go all the way from 1.54-inch through to 12.2-inch size formats. If one of the larger sized displays is used in this specific application, then it will be necessary to incorporate an external RAM into the design, so that the frame buffer resource can be accommodated. Displays with black and white or tricolour (black, white and red) can be considered, though use of the latter may prove to be more appropriate – as the additional colour will allow certain messages to be emphasised.
An example project based on the remote messaging unit arrangement described above can be found on Hackster.io. Here, the unit is comprised of an EXT3 board and 3.7-inch tricolour display, along with a Particle Photon board for the processing and providing wireless (Wi-Fi) communication. The back-end/dashboard for this example has been developed using Node-Red, which is an intuitive, visually-based programming platform intended for event-driven IoT applications. This avoids the need for engineers to have to write their own code.
By using EXT3 to evaluate and speed up prototype development time, EPD technology can be incorporated into numerous projects, offering designers a low-power, sunlight readable display option.
Read the full article in EPDT's July 2021 digital issue...
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