Differences between the JackAl and Nextion displays

Most people don’t understand and won’t want to understand the differences between different types of display technologies.

Unfortunately,  the µBITx community has fractured its user base amongst competing screen technologies.   There are many different types of LCD display screens and they are not compatible at all.   

Differences between the Nextion and JackAl displays have been discussed on the BITX20 IO Group list following discussion about whether a Nextion screen used with the KD8CEC firmware could be ported across to the JackAl.  The simple answer is “No”!

Brian N8BDB notes that  it’s not going to be as simple as replacing a driver and rebuilding the application.  The Nextion display works in a very different way than the normal displays most people use for microprocessors like arduino and teensy.

Normally the display is a “dumb” device that just handles displaying the dots.  Software libraries are used to provide basic functionality like drawing lines, boxes, and text.  Touch events are handled completely separately by other libraries.

The Nextion display is the opposite.  The display has it’s own microcontroller, memory, etc. and the arduino communicates with it through a serial interface.  All of the buttons, text, gauges, etc. are prebuilt in the Nextion editor.  The application doesn’t know where they are on the screen.  It just has a name such as “button1” that is associated with a button on a particular screen for instance.  The application just sends a command to the display to change the text of “button1” to “abcd”.  It would require a significant rewrite of the JackAl UI code to make it work with a Nextion display.

The other thing as Jack pointed out is about resolution.  The Nextion displays most people have are much lower resolution than the display used by the JackAl board.  The 2.4″ and 2.8″ Nextion displays are 320×240.  The 5″ Nextion display ($60) is the closest one with similar resolution (800×480) and that is 33% more in price than the display ($40) that JackAl currently uses.  Even the 4.3″ Nextion display is only 480×272.

There are pros and cons of both screen types.  The Nextion costs a bit more per pixel because it has a processor on board, but the demand (in terms of memory and processing power) on the main µBITx is minimal.   The processor and screen communicate using a series of codes.   The Nextion (in theory) can be adapted to have quite different user interfaces for the same functions.  There are, in fact, at least two distinctly different versions of “look and feel” available already.   However, setting up these requires a fairly steep learning curve on the screen management environment.

On the other hand, the JackAl screen (along with all other types of LCD screens) is strongly tied into the firmware of the JackAl teensy processor and amending the “look and feel” of the display requires detailed knowledge of the processor, firmware and the screen programming environment on which the JackAl is built.  It is unlikely that the Nextion will be ported across to the JackAl environment any time soon.  Bite the bullet and buy a new screen!

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