We created already a universal communication class in the last two episodes (Part 7 here and Part 8 here). It allows us with a little less than 60 lines of code in a separate .h file to handle one or even multiple Nextion HMIs connected to our MCU (Arduino or whatsoever), optionally using a second serial port for debugging each. And we can use this classes' cmdWrite() method to send commands to each of our connected Nextion HMIs without caring about the terminator which is automatically added. With this "Multiple Nextion HMIs on one Arduino", we went already beyond most existing libraries.Since, depending on our MCU and its number of serial ports, our class has alternatively to deal with HardwareSerial, SoftwareSerial, AltSoftSerial, USBSerial, we learned that the GNU C++11 compiler which is used by the Arduino IDE is a bit (in fact, very very) finicky about the type of passed object references (Serial, Serial1, Serial2, etc.) when it comes to construct depending objects like our NexComm class, we had the occasion to learn about template classes. We will need this knowledge later.

Hooray... this is the 30th edition of the NEXTION Sunday blog! But to our big surprise, it was the one published last week, talking about wrapping the Nextion communication functionality in a simple C++ class which had the double number of readers than other blog episodes during the first 7 days. Obviously, there are many people interested in having a simple .h file accompanying their main .ino (or .c or .cpp) file instead of linking a highly complex, heavy and specialized library. Enough motivation to move on!

Over the last weeks, we have seen how a few lines of Python or C++ (Arduino) code allowed us to fully control our Nextion HMI and how we could catch events happening there on the MCU (Arduino) side. Now, these were simple examples and if you remember well from episode 4, our code was compact and worked well, but this was for only one component on a single page. Also, episode 6 gave us the opportunity to "listen" to generic Touch Press and Touch Release events, but that's far from covering the full list of data which the Nextion HMI can send back to the MCU.Time to make things more flexible and to de-clutter our Arduino Sketches. You may naturally use the official Nextion Library, but if you are like me and you want to understand how things work and you want to remain in control of every.single.byte, you are cordially invited to read this and the coming episodes and follow the idea of modularizing our elementary functions and to wrap them up in a few classes. I don't know yet where this will end, but odds are good that we end up with a simple, flexible, and compact miniature edition of a Nextion library which we will fully understand since we have written it ourselves, and which at the same time overcomes some restrictions of the actual library.

Over the last blog episodes we have made our Arduino talk to the Nextion HMI. We even managed to build a simple digital volt meter using just an Arduino and a Nextion. But up to now, we never cared about what the Nextion HMI would have to tell to the Arduino. So, let's attack things from the other side today, and capture the data sent by the Nextion!

In the last episode, we saw how the Arduino could basically send commands over to the Nextion, and we used that for displaying some funny animated texts. Before we move on, it will be needed to look critically back on our code and eliminate some "not so optimal" things. But we will end up with a simple digital volt meter today, and I guess it's worth it.

As promised in last Sunday's blog episode, where we controlled our Nextion HMI directly from our PC using the Python3 command window, we are now up for a few episodes where we'll see in detail, how to hook up and program an Arduino. Over the next weeks, we'll see step by step how to make an Arduino talking to a Nextion, without using a prefabricated library, just by using the well documented ASCII command format. At the same time, this approach allows us to review some basics of the Arduino C/C++ dialect.