A character LCD shows letters and numbers line by line. This guide explains how to use an HD44780-compatible character LCD fitted with a PCF8574 I²C adapter module with the built-in Iclcd…() functions on ILOGICS industrial Arduino products. You do not need to add ILIB.h, CLCD.h, Wire.h, or an LCD object to your sketch.

Check the connections in the order below, enter your LCD's actual I²C address and number of columns and rows, then upload the example. The address 0x27 and the size 20 × 4 are example values on this page, not values shared by every LCD. A 16 × 4 LCD is outside the scope of this guide, because rows 3 and 4 do not match the positions the built-in functions calculate.

1. Install the ILOGICS Arduino SDK as described in Getting Started with Arduino IDE, and select the board and port for your product.
2. With the power off, connect the product's I²C terminals to the LCD adapter module. See your MPINO or MPAINO product page for the terminal location and power output rating.

On MPINO-16A8R, take +5V and GND from the POWER terminal. Its +5V output is limited to 100 mA, so first check the LCD's current, including the backlight.

The figure shows the part of the MPAINO CPU module I²C wiring diagram needed for the LCD. The diagram and terminal information come from the MPAINO-16A16R product page.

On the MPAINO CPU module, SDA is D20 and SCL is D21. Numeric pin numbers on MPINO differ by model, so do not apply these values to MPINO. Follow the actual SDA and SCL terminals and the product page. While using I²C, do not use the same SDA and SCL as external interrupt or encoder inputs.

Initialize the LCD with IclcdBegin(address, columns, rows) before using output functions. address is the 7-bit I²C address of the LCD adapter module, columns is the number of characters per line, and rows is the number of lines. The accepted argument range is 1~40 columns and 1~4 rows. This does not mean that every LCD size has supported row addresses. In the current core, the start addresses of rows 3 and 4 are fixed at 0x14 and 0x54, which do not match rows 3 and 4 of a 16 × 4 LCD. IclcdBegin() returns false if the address, size, or device number is invalid, or if a required I²C transfer gets no response.

Every function returns success or failure as a bool. To tell up to four LCDs apart, use device numbers 0~3. If omitted, the device number is 0. Each device must first be started with its own address using IclcdBegin(address, columns, rows, backlight, device). The default for backlight is true.

In IclcdPrint(), the second argument for a string is the device number. For an integer, the second argument is the base (BIN, OCT, DEC, HEX, or 2~36). For a real number, it is the number of decimal places (0~10). In these two forms the device number is the third argument. For example, IclcdPrint(“SUB”, 1) writes a string to device 1, and IclcdPrint(255, HEX, 1) writes FF to device 1.

This example is for an LCD with I²C address 0x27 and 20 columns × 4 rows. If your LCD has a different address, replace 0x27 with the address you confirmed. For other screen sizes, check the row address limit above and the LCD documentation first, then change the column and row values. Do not use this example on a 16 × 4 LCD. In Arduino IDE, open File → New Sketch, paste the complete code, save it, then select Verify (✓) and Upload (→) in that order.

void setup() {
  Serial.begin(115200);
 
  // Replace these with your LCD adapter's I²C address, columns, and rows.
  if (!IclcdBegin(0x27, 20, 4)) {  // Initialize the LCD and check the I²C response.
    Serial.println(F("LCD connection failed"));
    return;
  }
 
  IclcdSetCursor(0, 0);       // Move to the first position on line 1.
  IclcdPrint(F("ILOGICS"));   // Write text on line 1.
  IclcdSetCursor(0, 1);       // Move to the first position on line 2.
  IclcdPrint(F("LCD READY")); // Write text on line 2.
}
 
void loop() {
}

After uploading, check that ILOGICS appears on line 1 and LCD READY on line 2. If nothing appears, open the Arduino IDE Serial Monitor at 115200 bps and check whether LCD connection failed is printed. That message means you should check the address, wiring, power, or I²C response. true from IclcdBegin() means the I²C transfers got a response. It does not check whether characters are actually visible on the screen.

This sketch tries the address ranges of PCF8574 modules with IclcdBegin() and prints each address that responds. With the LCD connected, upload it and open the Serial Monitor at 115200 bps. Then enter the printed address in the example above. If only Done is printed, no module responded, so check the wiring and power. If Done does not appear either, restart the product with the Serial Monitor open.

void setup() {
  Serial.begin(115200);
  delay(1000);
 
  for (uint8_t address = 0x20; address <= 0x3F; address++) {
    if (address == 0x28) address = 0x38;  // Skip the range PCF8574 modules do not use.
    if (IclcdBegin(address, 20, 4)) {
      Serial.print(F("Response at 0x"));
      Serial.println(address, HEX);
    }
  }
  Serial.println(F("Done"));
}
 
void loop() {
}

These functions use the PCF8574 connection P0 = RS, P1 = R/W, P2 = Enable, P3 = backlight, P4~P7 = LCD D4~D7. If your adapter module uses a different mapping, it may not display correctly even when the I²C address is right. IclcdCommand() changes the screen state directly, so use it only if you know HD44780 commands.

For the arguments and examples of each function, select its name in the table above. For product terminals and power ratings, your MPINO or MPAINO product page takes priority.