New skill for building legacy hardware cicuit mockups

2026-02-23 20:05:12 +00:00 · 2026-01-18 23:16:45 -05:00
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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/>
+
+---