2026-10-12 23:55:15 +02:00
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# Arduino Nano: flipdot driver
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PlatformIO environment: `nano`
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The Nano is connected directly to the Brose panel electronics. It keeps an 84 × 19 frame
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buffer and takes drawing commands over serial (115200 baud). It has no clock or network
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logic.
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## Behaviour
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2026-10-13 00:00:56 +02:00
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- **Boot:** the Nano flips the whole display on and then off, then prints the time a full
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redraw took.
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2026-10-12 23:55:15 +02:00
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- **`display()`:** compares the new buffer with the last one that was shown and strobes
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only the dots that changed.
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- **Every 2 minutes** (`REFRESH_TIME`) it forces a full redraw to fix dots that got stuck.
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- **Flip pulse length** (µs) is set with the `T` command and stored in EEPROM, so it is
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kept after a reboot.
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## Serial protocol
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Each command is one ASCII line. Coordinates are 2-digit **hex**. Color is `0` (black) or
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`1` (yellow). The ESP32 driver (`ESPSERIAL`) only uses `s`, `S`, `F`, `D` and `T`.
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| Cmd | Format | Meaning |
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|-----|--------|---------|
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| `s` | `sXXYYc` | Set pixel in the buffer |
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| `S` | `SXXYYc` | Set pixel and flip it right away (direct mode) |
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| `F` | `Fc` | Fill the whole buffer |
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| `D` | `D` | Push the buffer to the display (changed dots only) |
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| `P` | `PXXYYcsTEXT` | Print text at (XX,YY), color `c`, size `s`. `\n` in TEXT starts a new line. |
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| `B` | `BXXYYWWHHcHEX...` | Draw a bitmap. WW must be a multiple of 4. Pixel data is one hex digit per 4 pixels. |
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| `R` | `R` | Print the buffer as ASCII art on the serial port |
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| `T` | `Tnnn` | Set the flip pulse length in µs (decimal), stored in EEPROM |
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Example (what the ESP32 sends for one pixel and a refresh):
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```
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s0a051
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D
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```
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## Wiring (default pinout)
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The pins are defined in [lib/BROSE9323/BROSE9323.h](../../lib/BROSE9323/BROSE9323.h).
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If you use the PLCC adapter board, build with `-D FLIPDOT_PLCC_ADAPTER` to switch to its
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pinout.
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| Signal | Nano pin |
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|--------|----------|
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| ENABLE | D7 |
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| ADDR_0 / 1 / 2 (panel select) | D3 / D5 / D6 |
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| COL_DATA | D4 |
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| COL_0 … COL_4 | D8, D10, D9, D11, D12 |
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| ROW_0 … ROW_4 | A3, A4, A2, A0, A1 |
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| ROW_RESET | D13 |
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| ROW_SET | A5 |
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| Serial RX | D0 (from ESP32 TX) |
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