Another morse decoder
The goal is to be able to decode a morse signal in a -20db snr environment.
This is work in progress.
The input is on the line connector right channel, the one opposite to the earphone plug.
Input sensitivity: lineInLevel(0) = 3.12Vpp max range.
Debug inputs:
- pin 14 sync start
- pin 15 tone
Debug outputs:
- line left channel
- line right channel
The TFT display (320x240, ILI9341) is divided into three zones:
- Top: Decoded Morse text output (3 lines)
- Middle: Menu with 4 function rows + scope bar
- Bottom: Software version
| Row | Function | Parameter Values |
|---|---|---|
| 0 | Out Left | 11 sources: POWER, I_SAMPLES, Q_SAMPLES, PHASE, SUBSAMP, DETECT, UNFILT_P, BESSEL, PRE, INPUT, SIG INT |
| 1 | Out Right | Same 11 sources |
| 2 | Gain | 0.1, 1.0, 10.0 (controls I2S output gain) |
| 3 | Sig Gen | 1.0, 0.0, -1.0, 0.9Hz, 9Hz, 90Hz, 900Hz (internal signal generator) |
| 4 | Marge | Detection threshold, 0.005 increments (calls set_threshold()) |
| 5 | Scope | Button triggers serial CSV output |
A rotary encoder navigates the menu; pushing it enters/exits parameter edit mode.
All-F32 audio path using OpenAudio_ArduinoLibrary:
AudioInputI2S_F32→AudioCoherentDemod4x_F32(9 demodulator outputs)- Signal sources routed through
AudioMixer11_F32(11-input mixer) toAudioOutputI2S_F32 - Additional sources: INPUT (raw Line In), SIG INT (internal signal generator)
- Output gain controlled via
AudioOutputI2S_F32.setGain() AudioCoherentDemodSegmented4x_F32: alternative demodulator using Hann-windowed overlap analysis for cleaner I/Q extraction — same 9-output interface, drop-in compatible
Between the menu and the version line, a 4-trace oscilloscope view shows signal levels vs time:
- Pin 14 sync (green) and Pin 15 tone (cyan): superposed digital traces sharing the same vertical band. A rising edge on pin 14 triggers the sweep.
- Detection (magenta): binary trace from
get_last_detection(). - Power (yellow): analog trace (0.0–1.0) from
get_last_power(). - Sweep rate: 10ms/pixel, 300 pixels wide = 3.0 seconds.
- A 5th menu row controls the scope: pressing the button outputs one sweep of tab-separated serial data (
Time Sync Tone Detect Power).
Connect at 115200 baud. Available commands:
help— list commands, source names, and signal generator modesstatus— show current settings (outputs, gain, siggen, marge)set out<N> <source>— assign source to output 0-1 (e.g.set out0 INPUT)set gain <value>— set output gain (0.1, 1.0, or 10.0)set siggen <mode>— set signal generator mode 0-6set marge <value>— set detection threshold (e.g.set marge 0.3)scope— output next oscilloscope sweep as tab-separated CSV
| Pin | Function | Notes |
|---|---|---|
| 0 | Encoder B | Rotary encoder rotation |
| 1 | TFT RST | ILI9341 display reset |
| 2 | TFT DC | ILI9341 data/command |
| 3 | Encoder A | Rotary encoder rotation |
| 4 | TUNESW | Encoder push button (INPUT_PULLUP) |
| 5 | LED | Signal/tuning indicator |
| 6 | (reserved) | Audio Shield SPI flash MEMCS |
| 7 | I2S RX | Audio Shield SGTL5000 |
| 8 | I2S TX | Audio Shield SGTL5000 |
| 9 | (reserved) | Audio Shield SD card CS |
| 10 | TFT CS | ILI9341 SPI chip select |
| 11 | SPI MOSI | ILI9341 display |
| 12 | SPI MISO | ILI9341 display |
| 13 | SPI SCLK | ILI9341 display |
| 14 | Digital input 1 | Available |
| 15 | Digital input 2 | Available |
| 16 | — | Available |
| 17 | — | Available |
| 18 | I2C SDA | SGTL5000 control (Wire) |
| 19 | I2C SCL | SGTL5000 control (Wire) |
| 20 | I2S LRCLK | Audio Shield SGTL5000 |
| 21 | I2S BCLK | Audio Shield SGTL5000 |
| 22 | — | Available |
| 23 | I2S MCLK | Audio Shield SGTL5000 |
Processing in python seems to work, see below 10WPM @ -20db snr, transmit data is : "ios" (.. --- ...)
