Teensy 4.1 Serial RX/TX Send & Receive with Nextion Display

[Peterschnecke]

Hi everyone,

I've got a problem, trying to get my Teensy 4.1 and my Nextion NX8048K070-011C Display to communicate.

The Nextion Display gets programmed with a GUI. In this GUI is a debug Mode, that virtualizes the Display on the PC. This virtual Display can use the USB-Serial Port of the Teensy to communicate with it.
The virtual software display can communicate flawlessly with the Teensy via the USB serial interface.

But when I try to use the actual hardware display, the serial communication between display and Teensy does not work.

The display is powered by a USB powerbank with 5V.
The TX and RX are connected to port 0 and 1 with Serial1 or to 7 and 8 with Serial2.

If I'm not mistaken both the Display and the Teensy use 3,3V on the Serial Connection

https://nextion.tech/datasheets/nx8048k070/#6

String BefehlENDE = String (char(0xff)) + String (char(0xff)) + String (char(0xff));       // This is the "EndOfCommand" so that the Display knows the Command ended
char Befehl;                                                                                                     // Variable that takes the Display input
#define HWSERIAL Serial2                                                                                   // Serial=SoftwareUSB  Serial1=Pin0&1  Serial2=7&8



void setup() {
  HWSERIAL.begin(9600);                       // Serial with 9600 Baud
  }

void loop() {
 while(HWSERIAL.available() < 1){}         
  Befehl = HWSERIAL.read();
 if( Befehl == 'A')
 {
  HWSERIAL.print("AusgabeTXT.txt=\"AN\"");         //If Display sends an 'A' , Send Command to print "AN" in the Textbox
  HWSERIAL.print(BefehlENDE);
 }
  if( Befehl == 'U')
 {
  HWSERIAL.print("AusgabeTXT.txt=\"AUS\"");       //If Display sends an 'U' , Send Command to print "AUS" in the Textbox
  HWSERIAL.print(BefehlENDE);
 }
  if( Befehl == 'N')
 {
  HWSERIAL.print("ZahlIN.val=0");                       //If Display sends an 'N' , Send Command to set the Number variable to 0
  HWSERIAL.print(BefehlENDE);
 }
  if( Befehl == '5')
 {
  HWSERIAL.print("ZahlIN.val=ZahlIN.val+5");        //If Display sends an 5 , Send Command to add +5 to the Number variable
  HWSERIAL.print(BefehlENDE);
 }
 }

I guess it is some kind of Hardware Problem, as it works when it's virtualized and uses the USB-Serial of the Teensy?


Thanks in advance

 

[BriComp]

I have written a library to communicate with the Nextion.
It has most of the I/O conditions covered but is in reality a skeleton Library which is intended to be expanded by the user.
You can see it here, In includes an example .ino file and an .hmi file.

 

[Peterschnecke]

Thank you for your reply. The Library looks great.

I also figured out my Problem, like stated, it worked in the simulation, but not on the actual device.
I simply misplaced the common ground on the breadboard. Stupid user error. Reconnected the common ground and everything worked.

 

[BriComp]

The Library looks great.

Thanks for that, I was trying to make it as flexible as possible and also easy to use.

I simply misplaced the common ground on the breadboard.

I did a similar thing in the past! Was spending so much time and attention at RX/TX orientation that I completely forgot about the earth return. What made investigation frustrating was that it would work, but intermittently, returning good then bad then good etc.