# DFRobot FIT0127 LCD Character Display Specification

## 1. Overview

The **DFRobot FIT0127** is a family of **HD44780-compatible character LCD modules** commonly used in embedded systems and hobbyist projects. These displays provide alphanumeric output using a dot-matrix character generator and support both 8-bit and 4-bit parallel interfaces.

FIT0127 modules are frequently paired with microcontrollers and 8-bit CPUs such as the **6502**, **AVR**, **PIC**, and **Arduino** platforms.

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## 2. General Characteristics

| Feature           | Description                                         |
| ----------------- | --------------------------------------------------- |
| Display type      | Character LCD (STN, Yellow-Green backlight typical) |
| Controller        | HD44780 or compatible                               |
| Interface         | Parallel (4-bit or 8-bit)                           |
| Character size    | 5 x 8 dot matrix                                    |
| Operating voltage | 5 V logic (some variants support 3.3 V)             |
| Backlight         | LED (separate power pins)                           |
| Viewing mode      | Transflective                                       |

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## 3. Display Variants

The FIT0127 designation is commonly associated with **16x2 character LCD modules**.

| Variant | Characters          |
| ------- | ------------------- |
| FIT0127 | 16 columns x 2 rows |

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## 4. Pin Configuration

### 4.1 Pinout (Standard 16-pin Header)

| Pin | Name | Description           |
| --: | ---- | --------------------- |
|   1 | VSS  | Ground                |
|   2 | VDD  | +5 V supply           |
|   3 | VO   | Contrast adjust       |
|   4 | RS   | Register Select       |
|   5 | R/W  | Read/Write select     |
|   6 | E    | Enable                |
|   7 | D0   | Data bit 0            |
|   8 | D1   | Data bit 1            |
|   9 | D2   | Data bit 2            |
|  10 | D3   | Data bit 3            |
|  11 | D4   | Data bit 4            |
|  12 | D5   | Data bit 5            |
|  13 | D6   | Data bit 6            |
|  14 | D7   | Data bit 7            |
|  15 | A    | Backlight Anode (+)   |
|  16 | K    | Backlight Cathode (-) |

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## 5. Electrical Characteristics (Typical)

| Parameter           | Value       |
| ------------------- | ----------- |
| Logic voltage (VDD) | 4.5 - 5.5 V |
| Logic current       | ~1-2 mA     |
| Backlight voltage   | ~4.2 V      |
| Backlight current   | 15-30 mA    |

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## 6. Interface Signals

### 6.1 RS (Register Select)

| RS | Function             |
| -- | -------------------- |
| 0  | Instruction register |
| 1  | Data register        |

### 6.2 R/W

| R/W | Operation     |
| --- | ------------- |
| 0   | Write to LCD  |
| 1   | Read from LCD |

### 6.3 Enable (E)

* Data is latched on the **falling edge** of E
* E must be pulsed HIGH  LOW for each transfer

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## 7. Data Bus Operation

### 7.1 8-bit Mode

* Uses D0-D7
* Faster operation

### 7.2 4-bit Mode

* Uses D4-D7 only
* Data transferred in two nibbles (high first)
* Saves I/O pins

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## 8. Internal Memory Map

### 8.1 DDRAM (Display Data RAM)

|   Address | Display Position |
| --------: | ---------------- |
| 0x00-0x0F | Line 1, Col 1-16 |
| 0x40-0x4F | Line 2, Col 1-16 |

### 8.2 CGRAM (Character Generator RAM)

* Supports up to **8 custom characters**
* Each character uses 8 bytes

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## 9. Instruction Set (Summary)

| Instruction | Description            |
| ----------- | ---------------------- |
| 0x01        | Clear display          |
| 0x02        | Return home            |
| 0x04-0x07   | Entry mode set         |
| 0x08-0x0F   | Display on/off control |
| 0x10-0x1F   | Cursor/display shift   |
| 0x20-0x3F   | Function set           |
| 0x40-0x7F   | Set CGRAM address      |
| 0x80-0xFF   | Set DDRAM address      |

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## 10. Initialization Sequence (4-bit Mode)

```text
Wait >15 ms after VDD rises
Function set: 0x33
Function set: 0x32
Function set: 0x28 (4-bit, 2-line)
Display ON/OFF: 0x0C
Entry mode: 0x06
Clear display: 0x01
```

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## 11. Timing Characteristics (Typical)

| Operation          | Time     |
| ------------------ | -------- |
| Enable pulse width | ≥ 450 ns |
| Command execution  | ~37 µs   |
| Clear / Home       | ~1.52 ms |

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## 12. Typical System Integration (6502 Example)

```text
RS   VIA output
E    VIA output
D4-D7  VIA Port B
R/W  Grounded (write-only)
```

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## 13. Contrast and Backlight Control

* Contrast adjusted via potentiometer on VO pin
* Backlight may require series resistor
* PWM dimming supported via external control

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## 14. Absolute Maximum Ratings (Summary)

| Parameter      | Rating                |
| -------------- | --------------------- |
| VDD            | -0.3 V to +6.0 V      |
| Input voltage  | -0.3 V to VDD + 0.3 V |
| Operating temp | -20 °C to +70 °C      |

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## 15. Common Use Cases

* Status displays
* Debug output for SBCs
* User interfaces for embedded systems
* Retrocomputer front panels

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## 16. References

* <https://static6.arrow.com/aropdfconversion/1f68489996f057bb6611f71d5fdb5f60f44faa72/pgurl_58439499065092.pdf>
* <https://cdn.sparkfun.com/assets/9/5/f/7/b/HD44780.pdf>
* <https://predictabledesigns.com/introduction-embedded-electronic-displays/>

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