136 Morse Code Keyer
136 : Morse Code Keyer
- Author: Brady Etz
- Description: Convert a keyed CW input to morse tones and 7-segment character output
- GitHub repository
- Open in 3D viewer
- Clock: 12000000 Hz
How it works
Morse Keyer takes a paddle-type dit/dah signal (io[0:1]) and converts it to an auxilliary Morse code output (io[4]) and a buzzer tone (io[5]). The design outputs auxilliary dit/dah signals (io[2:3]) to send to other gear, like a radio. Additionally, it outputs to the demonstration board's seven-segment display (out[7:0]) to reveal the character you just completed as you key.
To use a straight-key input (or press a single button to key Morse code) set in[0] HIGH. For Iambic paddles, set in[0] LOW. To use Iambic keying type A, set in[1] LOW. For Iambic-B, set in[1] HIGH. (https://ag6qr.net/index.php/2017/01/06/iambic-a-or-b-or-does-it-matter/) WPM control is set between 7 WPM and ~100 WPM with in[7:4] via the demo board dip switches. The timing element in this system divides the system clock first with a 512x prescaler, then feeds it into the variable delay below:
| Control [7:4] | WPM | Clocks | Timer Preset |
|---|---|---|---|
| 4'b0000 | 110.3 | 255 | 12'b000011111111 |
| 4'b0001 | 55.0 | 511 | 12'b000111111111 |
| 4'b0010 | 36.7 | 767 | 12'b001011111111 |
| 4'b0011 | 27.5 | 1023 | 12'b001111111111 |
| 4'b0100 | 22.0 | 1279 | 12'b010011111111 |
| 4'b0101 | 18.3 | 1535 | 12'b010111111111 |
| 4'b0110 | 15.7 | 1791 | 12'b011011111111 |
| 4'b0111 | 13.7 | 2047 | 12'b011111111111 |
| 4'b1000 | 12.2 | 2303 | 12'b100011111111 |
| 4'b1001 | 11.0 | 2559 | 12'b100111111111 |
| 4'b1010 | 10.0 | 2815 | 12'b101011111111 |
| 4'b1011 | 9.2 | 3071 | 12'b101111111111 |
| 4'b1100 | 8.5 | 3327 | 12'b110011111111 |
| 4'b1101 | 7.9 | 3583 | 12'b110111111111 |
| 4'b1110 | 7.3 | 3839 | 12'b111011111111 |
| 4'b1111 | 6.9 | 4095 | 12'b111111111111 |
WARNING: The auxilliary Morse output MUST NOT be used as a raw radio TX control for a homemade radio. This is because the keying interface must control the transmitted wave shape to maintain acceptable RF bandwidth. Be a good RF neighbor. Always use the provided keyer inputs for your radio. These are typically provided with a 3.5mm TRS jack, with Sleeve = GND, Ring = Dah, and Tip = Dit/Straight.
Most radio systems use active-low / open-collector signaling to protect systems operating at various supply voltages. Please see the External Hardware section for recommendations.
How to test
Set the input clock frequency to 12 MHz. Set the dip switches (in[7:0]) on the dev board to the desired paddle setup and WPM rate. Attach hardware like that shown in the External Hardware section to use.
External hardware
For the best experience, and to use custom radio hardware and paddles, I recommend assembling a companion PCB affixed the bidirectional PMOD.
A /pcb/ directory accompanies the standard Tiny Tapeout directories with the KiCad files.
Please see the schematic below for a screenshot of the recommended application schematic:
IO
| # | Input | Output | Bidirectional |
|---|---|---|---|
| 0 | Paddle Selection (1 = Iambic) | 7-Seg. Display A | External Dit / Straight In (active-high) |
| 1 | Iambic-A/B Type Selection (1 = B) | 7-Seg. Display B | External Dah In (active-high) |
| 2 | 7-Seg. Display C | Aux. Dit Paddle Out (active-high) | |
| 3 | 7-Seg. Display D | Aux. Dah Paddle Out (active-high) | |
| 4 | WPM Select [0] (LSB) | 7-Seg. Display E | Aux. Morse Out (active-high) |
| 5 | WPM Select [1] | 7-Seg. Display F | Buzzer Tone Out |
| 6 | WPM Select [2] | 7-Seg. Display G | |
| 7 | WPM Select [3] (MSB) | 7-Seg. Display . |