YO4HFU |
ISD1760 Voice Keyer & Roger Beep |
SHF Skeeds? Add a "Parrot" Voice Keyer to Your Setup!
Enhance antenna alignment, CQ calling, or rain scatter testing with a "parrot" voice keyer. This device is inspired by the BX-184, with additional features and simplified operation. Best of all, it's free for DIY amateurs!
The project uses ISD1760SYI (SOIC-28 package), ordered directly from NUVOTON (Taiwan). The performance achieved is comparable with similar chip sourced from Aliexpress, even if the appearance of the IC capsule is not identical.
Key Features:
- Built-in electret microphone for recording and bypass mode (feed-through)
- Voice recording up to 60 seconds with an 8KHz sampling rate (optional 40 seconds / 12KHz)
- Multifunctional key for mode selection: BYPASS / PLAY LOOP / BEACON / RECORDING
- Adjustable "beep" tail (50–600ms), enabled/disabled by jumper
- Tone frequency selection: 800Hz / 1000Hz via jumper
- Beacon mode for continuous CW transmission (1 sec. length, 0.5 sec. spacing) — useful for microwave testing, antenna alignment, etc.
- Fixed delay time in PLAY LOOP mode (5 sec. receiving period)
- Open collector output to control radio's PTT
- Arduino IDE compatible, using the ATtiny84 microcontroller and ATTinyCore 2.0 board library
- Free firmware and Arduino sketch provided
- PCB 23 x 26mm
HOW TO USE:
Description of SELECT "PB2" functionality:
PLAY LOOP (short press: 0.5–3 sec) / BEACON (medium press: 3–6 sec) / RECORDING (long press: >6 sec)
1. BYPASS MODE
After powering on, the voice keyer defaults to BYPASS MODE, routing the integrated microphone to the radio's MIC input (feed-through mode). Audio quality remains unaffected by the ISD IC, and only the "beep" tail is active in this mode.
Moreover, the internal AGC circuit provides a pleasant compression effect, making the modulation more punchy.
2. RECORDING MODE
To record your voice message, hold the SELECT key for more than 6 seconds. The extended hold time helps to prevent accidental erasure. LED "Ready to REC" will be activated. If necessary, release and press SELECT again to cancel recording.
Press the PTT key (erasing any previous ISD content), then speak your message. Release PTT to save it; the maximum track length is 60 seconds. During recording, PTT_OUT is disabled, so the radio’s TX will not activate.
The recorded message length is saved in the ATtiny84 EEPROM as a reference for PLAY LOOP mode. LED "Ready to REC" will be deactivated when recording mode is no longer selected.
3. PLAY LOOP MODE
To play the recorded message, press SELECT for 0.5–3 seconds. The PLAY routine activates, enabling PTT_OUT and activating the radio’s TX. After the message finishes, the radio switches to RX mode for 5 seconds to check band activity, then repeats the cycle. Press PTT or SELECT to exit PLAY LOOP mode.
4. BEACON MODE
To activate BEACON MODE, press SELECT for 3–6 seconds. One-second CW tones are generated in a loop with a 0.5-second spacing. PTT_OUT is continuously enabled during BEACON MODE. Press PTT or SELECT to exit.
The "beep" tail is generated after each PLAY message or PTT release. By default, this function is enabled; close J1 to disable it. The default beep and beacon tone frequency is 800Hz, but closing J2 changes it to 1000Hz. Adjust length between 50–600ms using the "AUX" trimmer. MIC and BEEP levels can be adjusted independently; avoid overdriving the radio's microphone input. The SELECT key should be installed on the microphone body, or any other non-essential push button can be repurposed. It can be marked as "PBR".
Just as curiosity, ISD1760 SPI commands:
Power Up = 0x01
Configuration Feed-through Enabled = [0x65, 0xB0, 0x05]
Configuration Feed-through Disabled = [0x65, 0xF0, 0x05]
Play= [0x40, 0x00]
Stop = [0x02, 0x00]
Erase = [0x43, 0x00]
REC = [0x41, 0x00]
Schematic v1
PCB files (Gerber)
ISD1760 prototype PCB bottom
Voice Keyer installed inside MC-43S
Attiny84 firmware vers.6 (hex)
Attiny84 fuse bits
ISD1760 vers.6 sketch - free to be modified
Attiny84 board support, >>Link to ATTinyCore 2.0<<
yo4hfu@2010-2024