Implements MDC-1200 single and double-packet TX as a PPMA external app.
Features:
- Supports PTT ID, Emergency, Radio Check, Stun/Unstun, Call Alert,
Selective Call (1 & 2), Status Request/Response, Remote Monitor, Message
- Auto-fills Arg byte on Op selection
- AFSK FSK modulation: 1800 Hz mark / 1200 Hz space, 1200 baud
- NRZI encoding with Golay FEC per MDC-1200 spec
- Tap-to-edit frequency via keypad
- Default TX gain of 30 dB
- Uses AFSK baseband (same as POCSAG/SAME TX)
- All buffers kept off the stack to avoid hard faults in ext app environment
* mdc_tx: address PR review feedback
- Move MDC helpers into ui::external_app::mdc_tx namespace (drop anonymous namespace)
- Use AFSK_TX_SAMPLERATE macro instead of hardcoded 1536000
- Add #include "modems.hpp" explicitly for AFSK_TX_SAMPLERATE
- Replace n*8/n*16 pixel positions with UI_POS_X/UI_POS_Y macros
- Fix field comments: 'hex bytes' -> 'decimal bytes (0-255)'
- Fix TransmitterView frequency_step: 1750000 -> 12500 (12.5kHz NFM step)
- Fix MDC preamble: replace leading 0x00 bytes with 0xAA
after NRZI encoding stayed 0x00, terminating TX on the first word.
0xAA bytes NRZI-encode to 0xFF (continuous 1800Hz mark tone), which
is the standard MDC-1200 preamble and does not trigger the sentinel.
Sarah Rose
5c2d1d3dfb