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# 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.
---
## 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 |
---
## 3. Display Variants
The FIT0127 designation is commonly associated with **16x2 character LCD modules**.
| Variant | Characters |
| ------- | ------------------- |
| FIT0127 | 16 columns x 2 rows |
---
## 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 (-) |
---
## 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 |
---
## 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
---
## 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
---
## 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
---
## 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 |
---
## 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
```
---
## 11. Timing Characteristics (Typical)
| Operation | Time |
| ------------------ | -------- |
| Enable pulse width | ≥ 450 ns |
| Command execution | ~37 µs |
| Clear / Home | ~1.52 ms |
---
## 12. Typical System Integration (6502 Example)
```text
RS  VIA output
E  VIA output
D4-D7  VIA Port B
R/W  Grounded (write-only)
```
---
## 13. Contrast and Backlight Control
* Contrast adjusted via potentiometer on VO pin
* Backlight may require series resistor
* PWM dimming supported via external control
---
## 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 |
---
## 15. Common Use Cases
* Status displays
* Debug output for SBCs
* User interfaces for embedded systems
* Retrocomputer front panels
---
## 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/>
---