How do I wire my LCD screen to my NPK sensor where the data from the NPK sensor shows up on the LCD screen? I already have a wiring diagram but i don't know how to connect my LCD to the NPK sensor
For development I would not connect the RS485 module to the Uno hardware serial (pins 0 and 1). I would use a software serial port for the RS-485 and keep the hardware serial for program upload, program debugging and monitoring program output.
You can receive the data from the sensor through the rs-485 and then using the lcd.print function to send data to the LCD and lcd.setCursor to position the data. A LCD tutorial
My favorite LCD library is the hd44780 library. It includes a class for the 4 pin interface. The library is available through the IDE library managers. How to install an Arduino library. Use the hd44780_pinIO class
Once that you have installed the library here is the path to the documentation and example code for the pin IO class.
To add to the advice already given, you need a common ground connection between your NPK sensor and your UNO.
I would suggest you get your NPK sensor code working first. Output the NPK values to the serial port with standard print statements.
Once you have that going, introduce your LCD into the mix and adjust the print statements accordingly.
If you get stuck with your NPK sensor, then search the forums for NPK as there have been many discussions in the past.
If not in pin 0 and 1, where would you suggest putting the R0 and DI of the rs485?
Any 2 free pins can be used as RX and TX. Treat a software serial port the same as a hardware port except limited to half-duplex and maximum 38400 baud (Uno). The SoftwareSerial library comes with the IDE and there are other software serial libraries available.
Search for "Arduino SoftwareSerial tutorial" to learn how to use serial.
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