FactoryTest_wMenu, Test 3 LCD (I2C), Should Detect Missing LCD

[ForrestErickson]

Is your feature request related to a problem? Please describe.
A clear and concise description of what the problem is. Ex. I'm always frustrated when [...]

The test 3 passes even when there is no LCD soldered on to the assembly.

Describe the solution you'd like
A clear and concise description of what you want to happen.

The test should report success for the I2C address
The test should report FAIL for the LCD.

[ForrestErickson]

From an AI

AI Overview
While most standard Arduino LCD libraries are designed for writing to the display, reading back data is possible but not commonly done and requires specific hardware connections. The built-in LiquidCrystal library does not support this, but the hd44780 library does, provided the R/W (Read/Write) pin is properly wired to an Arduino I/O pin.
Why Reading is Generally Avoided
Typically, the Arduino code "knows" what it has written to the display, making reading unnecessary. Connecting the R/W pin to ground, which is common in many basic tutorials to force a "write-only" mode, simplifies the wiring but disables the read function.
Using the hd44780 Library for Reading
The hd44780 library, a highly regarded third-party library, provides functions for reading the display's internal memory and status registers.
Hardware Requirements:
You must connect the R/W pin of the LCD to an available digital pin on your Arduino (e.g., pin 10) instead of grounding it.
You must use all the required data pins (e.g., in 4-bit mode, you need RS, Enable, R/W, and 4 data lines, plus power/backlight pins).
Key Library Functions:
status(): Reads the LCD's status register, including the busy flag and the current DDRAM address.
read(): Reads a data byte from the LCD's data register.
Example (Conceptual)
To use the read functions, you first need to configure the library to use the R/W pin. The hd44780 library comes with examples, such as the ReadWrite example, that demonstrate this capability.
cpp
#include <hd44780.h>
#include <hd44780io.h> // Include the correct I/O class header

// Select the I/O class for your connection type (e.g., direct pin connection)
hd44780_pinIO lcd;

void setup() {
// Initialize the LCD with the appropriate function for your I/O class
lcd.begin(16, 2);
lcd.print("Hello, world!");
}

void loop() {
// Example of reading a character from a specific cursor position (DDRAM address)
lcd.setCursor(0, 0); // Set cursor to column 0, row 0

// Reading from the display
byte character = lcd.read();

// You can then process 'character' in your code
}
For detailed instructions and examples specific to your setup (parallel or I2C), refer to the official documentation and examples within the hd44780 library, which can be found in the Arduino Library Manager.

[ForrestErickson]

Another AI To test an I2C LCD display with an Arduino

AI Overview
To test an I2C LCD display with an Arduino, the recommended approach is to use the hd44780 library by Bill Perry, which includes a diagnostic sketch that automatically detects your display's configuration and I2C address. For parallel displays, use the built-in LiquidCrystal library and its "Hello World" example.
Testing an I2C LCD Display
Most modern LCD displays connect via an I2C "backpack" module, which only requires four wires (VCC, GND, SDA, SCL).

1. Install the hd44780 library
   This library is robust and features a diagnostic tool.
   Open the Arduino IDE.
   Go to Sketch > Include Library > Manage Libraries.
   In the search bar, type hd44780.
   Select the library by Bill Perry and click Install.
2. Wire the display
   Connect the I2C backpack pins to your Arduino:
   VCC to +5V
   GND to GND
   SDA to the I2C Data pin on your Arduino (e.g., A4 on Uno/Nano, pin 20 on Mega)
   SCL to the I2C Clock pin on your Arduino (e.g., A5 on Uno/Nano, pin 21 on Mega)
3. Run the diagnostic sketch
   This sketch will verify connectivity and identify the correct I2C address and pin mapping.
   In the Arduino IDE, go to File > Examples > hd44780 > ioClass > hd44780_I2Cexp > I2CexpDiag.
   Upload the I2CexpDiag sketch to your Arduino board.
   Open the Serial Monitor to view the diagnostic results. It will confirm if communication is working and provide the necessary parameters for your main code.
   Adjust the contrast using the potentiometer (usually a small blue cube with a screw) on the I2C backpack if you see a blank screen or solid boxes.