About

This is a modification of the Traquito Jetpack WSPR tracker firmware that turns the same low-cost jetpack hardware into a mixed-mode HF ground-station beacon. The code is experimental.

Disclaimer: most of the code modifications have been vibe-coded using Claude Code.

About the original code

Source code for the original Traquito Jetpack WSPR tracker — direct link.

That (and this) project relies heavily on picoinf.

This fork — summary of changes

• Mixed-mode sequential slot scheduling — configure an ordered list of up to 24 transmission slots. Each slot independently picks WSPR-2 (2-minute window, Type 1 only), WSPR-2 full grid (Type 1 + Type 3 back-to-back, one row, ~4 min), WSPR-2 compound (Type 2 + Type 3 back-to-back for a /P-style callsign), WSPR-15 (15-minute window), CW (fires immediately after the previous slot ends), IDLE (waits N minutes, no transmission), or REBOOT (resets the device). Slots fire back-to-back; the scheduler computes the next valid UTC-aligned window for each slot's mode so a mixed schedule "just works".
• WSPR full-grid resolution (Type 1 + Type 3) — a "WSPR-2 full grid" slot is a single row that transmits the standard Type 1 message (callsign + 4-char grid) immediately followed, in the same cycle, by the Type 3 message (hashed callsign + 6-character grid) — improving reported position resolution from grid square (~70×100 mi) to subsquare (~3×4 mi). Requires a 6-character grid in configuration. Encoder verified symbol-for-symbol against JTEncode.
• WSPR compound callsigns (Type 2 + Type 3) — a "WSPR-2 compound" slot beacons callsign + a single-character add-on suffix (e.g. SP5FLS/P, SP5FLS/2), which can't fit a Type 1 message. One row transmits a Type 2 message (compound call + power, no grid) immediately followed by a Type 3 message (compound call hashed + 6-char grid), same cycle. Needs the Add-on suffix field set and a 6-character grid. Encoder verified symbol-for-symbol against BD1ES's independent wspr_enc.c. Note: compound-callsign spots only resolve for receivers that caught the Type 2 (same wsprd session) — expect fewer usable spots than a plain base call; only use it if you actually need the suffix. Two-digit suffixes and add-on prefixes are not supported.
• IDLE slot — reserves a configurable wait (1–10080 minutes) on the schedule with no transmission and no radio/GPS activity. Useful for spacing cycles out (e.g. transmit, then go quiet for an hour) without the whole-cycle granularity of txInterval. Software-only — it does not put the microcontroller itself to sleep.
• REBOOT slot — for long-term unattended operation: performs a full MCU reset at a clean cycle boundary, clearing any accumulated software state (heap fragmentation, drift, wedged peripherals' driver state). Must be the last slot. idleMinutes doubles as a minimum uptime — the reboot only fires once the device has been up that long (0 = every cycle, 1440 = at most daily); otherwise the slot is a no-op. Skipped entirely in configuration mode so it never yanks the USB console. After reboot the beacon re-syncs GPS time and realigns the schedule automatically.
• Progress watchdog — beacon mode arms a software deadline every time a cycle is scheduled; if no new cycle gets scheduled within 30 minutes of the previous cycle's end, the device resets itself. Complements the 7-second hardware watchdog (which catches hard hangs) by catching "event loop alive but scheduler wedged" failures. The reset reason (power-on / watchdog / software reset) is logged at every boot.
• I2C bus recovery — runs at every boot before the transmitter's I2C bus is initialized. If the Si5351 was reset mid-transaction while holding the data line low (a state a plain MCU reset can't clear, since the chip itself isn't power-cycled), this manually clocks the bus free per the I2C-bus spec's standard recovery procedure. A no-op (single pin read) on every normal boot.
• CW beacon mode — CW slots auto-generate a K5RWK/B-style beacon message (VVV DE {call}/B {grid} × 3) for Reverse Beacon Network spotting. Per-slot frequency (Hz) and WPM are configurable. Fast Si5351 output-enable keying keeps transitions in ~50 µs.
• Per-slot UTC alignment — the scheduler always lands WSPR transmissions on the correct boundary for the slot's mode (even minutes for WSPR-2, multiples of 15 for WSPR-15). CW slots fire immediately with no alignment gap.

WSPR-15 is transmitted correctly but rarely decoded in practice. Its 0.18 Hz tone spacing needs the Si5351 reference to stay within a fraction of that over the full ~14.7-minute transmission; a bare crystal (no TCXO) drifts several Hz from self-heating alone during a continuous key-down, and almost no receivers run WSPR-15 and report to wsprnet. Prefer WSPR-2 / WSPR-2 full grid for reliable spots.

• Configurable TX interval — transmit every N cycles (1 = every cycle); a "cycle" is the full sequence of configured slots.
• No JavaScript / no telemetry — the JerryScript VM, per-slot JS, and user-defined telemetry messages have been removed. WSPR transmissions are standard Type 1 (callsign + 4-char grid + power), Type 2 (compound callsign), or Type 3 (hashed callsign + 6-char grid); no telemetry is encoded into the message.
• Ground-station orientation — the device is no longer a balloon tracker. The Maidenhead grid is user-entered in configuration; it is not auto-overwritten from GPS 3D fixes. CW uses the full 6-char grid; WSPR uses the first 4 chars.
• Transmits while USB/serial connected — no need to disconnect for the scheduler to run.
• Less verbose GPS output — raw NMEA GPS_LINE messages suppressed; GPS_FIX_TIME, GPS_FIX_2D, GPS_FIX_3D events still emitted.
• Less frequent temperature reading — polled every 30 seconds instead of every second.
• config.html — local web page to configure the beacon over Web Serial (Chrome/Edge 89+).

Use pre-compiled binaries

Pre-compiled .uf2 binaries are published in releases: https://github.com/filipsPL/TraquitoBeacon/releases/

To flash a .uf2 file:

1. Hold BOOTSEL on the Pico while plugging in USB — it mounts as RPI-RP2.
2. Copy TraquitoJetpack.uf2 to the drive. The device reboots automatically.

Note: This firmware uses a different on-flash configuration layout than older releases. After flashing, send {"type":"REQ_DELETE_CONFIG"} via serial (or click Erase flash config in config.html) to clear stale data, then reconfigure.

How to compile

Requires cmake, gcc-arm-none-eabi, libnewlib-arm-none-eabi, and build-essential.

# Install toolchain (Debian/Ubuntu)
sudo apt install cmake gcc-arm-none-eabi libnewlib-arm-none-eabi build-essential

# Clone and initialise all submodules
git clone <repo-url>
cd TraquitoJetpack
git submodule update --init --recursive

# Build
mkdir build && cd build
cmake ..
make -j$(nproc)

Output: build/src/TraquitoJetpack.uf2

Note: The ext/picoinf submodule contains local patches required for the Debian/Ubuntu toolchain. See Build fixes below if you reset or update the submodule. A patch file capturing all changes is at ext/picoinf.patch — apply with git apply ../../ext/picoinf.patch from inside ext/picoinf/.

Configuration

Via config.html and Web Serial

Open config.html directly in Chrome or Edge (89+). Click Connect, select the Pico's USB serial port, then use the form to read or save configuration. The page shows a live log of GPS fixes, temperature, and transmission events.

Tip

Web Serial requires Chrome/Edge 89+. Firefox is not supported.

Configuration fields:

Field	Description
Callsign	Amateur radio callsign (up to 6 characters)
Add-on suffix	Optional single character (0–9 / A–Z) for a WSPR-2 compound slot, e.g. P → SP5FLS/P; blank = plain callsign
Grid	Maidenhead locator, up to 6 chars (user-entered; not derived from GPS). WSPR uses first 4; CW beacon uses all 6.
Frequency correction	Signed Hz offset to compensate for Si5351 crystal error
TX interval	Number of cycles between active cycles (1 = every cycle)
Slot schedule	Ordered list of slots, each with its own mode (WSPR-2 / WSPR-2 full grid / WSPR-2 compound / WSPR-15 / CW / IDLE / REBOOT), band, channel or frequency, and WPM (or idle duration for IDLE, min uptime for REBOOT)

Slot schedule table — each row is one transmission. The Fires at column previews the minute-within-cycle each slot will run, assuming the cycle starts at :00. Use the ↑↓ buttons to reorder slots and × to remove. The cycle length is shown beneath the table (the schedule repeats indefinitely, UTC-aligned).

Via serial

Open a serial console:

tio --map INLCRNL,ODELBS --timestamp -e -b 115200 /dev/ttyACM0

Send JSON commands, e.g.:

{
  "type":"REQ_SET_CONFIG",
  "callsign":"SP5FLS",
  "correction":0,
  "grid":"IO85XW",
  "txInterval":1,
  "slots":[
    {"mode":0,"band":"20m","channel":414},
    {"mode":0,"band":"10m","channel":414},
    {"mode":1,"band":"20m","channel":5},
    {"mode":5,"band":"20m","channel":509},
    {"mode":2,"band":"20m","frequencyHz":14025000,"wpm":18},
    {"mode":3,"idleMinutes":30},
    {"mode":4,"idleMinutes":1440}
  ]
}

mode: 0 = WSPR-2, 1 = WSPR-15, 2 = CW, 3 = IDLE, 4 = REBOOT, 5 = WSPR-2 full grid (Type 1+3), 6 = WSPR-2 compound (Type 2+3).

For CW slots: frequencyHz is the exact transmit frequency in Hz; wpm is the keying speed (5–40). band is informational only (used for hardware filter selection).

For WSPR slots: channel selects the sub-band frequency via WsprChannelMap; frequencyHz and wpm are ignored.

For WSPR-2 full-grid slots (mode: 5): same band/channel as WSPR-2. This one configured slot fires a Type 1 message (callsign + 4-char grid) then, immediately after in the same cycle, a Type 3 message (hashed callsign + full 6-character grid) — ~4 minutes total. The configured grid must be 6 characters.

For WSPR-2 compound slots (mode: 6): same band/channel as WSPR-2. Set callsignSuffix at the top level to a single character (0–9 or A–Z); this one configured slot fires a Type 2 message ({callsign}/{callsignSuffix} + power, no grid) then, immediately after in the same cycle, a Type 3 message (that compound call hashed + the 6-character grid). Both a 1-character callsignSuffix and a 6-character grid are required.

For IDLE slots: idleMinutes (1–10080) is how long the scheduler waits before the next slot; no transmission occurs and band/channel/frequencyHz/wpm are ignored. This is a software wait only — the MCU is not put to sleep.

For REBOOT slots: idleMinutes (0–10080) is the minimum uptime in minutes before the reboot actually fires — below it the slot is a no-op and the cycle continues (0 = reboot every cycle, 1440 = at most daily). Must be the last slot and cannot be the only slot. Ignored in configuration mode (USB console stays up). All other fields are ignored.

Operational details

Scheduling

The scheduler is sequential and mode-aware. The user provides an ordered list of slots; the scheduler:

1. Waits for the next UTC window valid for slot 1's mode (even minute for WSPR-2, multiple of 15 for WSPR-15; immediate for CW/IDLE/REBOOT).
2. After slot N's transmission (or idle wait) ends, fires slot N+1 at the next valid UTC window for its mode — WSPR-to-WSPR may introduce a gap; CW/IDLE/REBOOT fire instantly.
3. When the last slot's transmission is actually over (a WSPR send finishes ~7 s before its 2-minute window closes), the cycle ends. The next cycle starts at the next valid UTC alignment for slot 1's mode — including a window that starts exactly where the last slot's window closes, so all-WSPR cycles chain back-to-back with no skipped window (e.g. three WSPR-2 slots repeat on a clean 6-minute period). Exception: when a GPS time resync is in progress at cycle end, a start window less than ~95 s away is deferred by one alignment period so the GPS gets time to lock.

The radio is warmed up (~30 s) before each slot when there is enough idle time; it is powered off after each slot and again at cycle end.

The TX interval setting skips N−1 complete cycles between active cycles.

Open question / known nuance: with very short cycles (e.g. 2 × WSPR-2 = 4 min total) txInterval=15 effectively means "transmit once an hour" — the unit is cycles, not minutes.

CW beacon

CW slots transmit the K5RWK/B-style beacon message:

VVV DE {call}/B {grid} {call}/B {grid} {call}/B {grid}

The message is auto-generated from the configured callsign and grid. At 18 WPM the full message takes approximately 20 seconds. CW Skimmer's optimal range is 15–40 WPM; the /B suffix puts spots in RBN's beacon-classified feed.

Recommended CW frequencies for RBN spotting:

Band	Frequency (Hz)	Rationale
30m	10 115 000	CW-only band, best HF skimmer coverage
20m	14 025 000	Dense skimmer coverage in the CW DX window
40m	7 025 000	Strong evening skimmer coverage

Frequency

For WSPR slots, output frequency is derived from each slot's configured band and channel via WsprChannelMap. For CW slots, frequencyHz is used directly. The frequency correction field (Hz) is applied on top of both to compensate for Si5351 crystal inaccuracy.

GPS and grid

• The device waits for a GPS time fix (UTC sync) before scheduling any transmissions. A 3D position fix is not required.
• GPS runs at startup and is shut off once a time fix (and optionally a 3D fix) is acquired. It is briefly re-enabled for a time-only resync whenever the last fix is more than 6 hours old, keeping WSPR window alignment within spec despite MCU crystal drift (~2–3 s/day unsynced).
• The Maidenhead grid used in transmissions is always the user-configured value in flash. GPS-derived position is logged but never overwrites the configured grid.

Config API

Command	Description
REQ_GET_CONFIG	Returns all configuration fields including the slot list
REQ_SET_CONFIG	Sets all configuration fields; the slots array fully replaces the prior list
REQ_DELETE_CONFIG	Erases stored config from flash and resets to defaults. Required after firmware upgrades that change the config struct layout.
REQ_GET_DEVICE_INFO	Returns firmware version and current mode (CONFIG or BEACON)
REQ_WSPR_SEND	One-shot test WSPR transmission: { band, channel, mode, callsign, grid, power }
REQ_RADIO_POWER_ON	Enable TX load switch (Si5351 power)
REQ_RADIO_POWER_OFF	Disable TX load switch
REQ_RADIO_OUTPUT_ENABLE	Enable TX + start RF output
REQ_RADIO_OUTPUT_DISABLE	Stop RF output
REQ_SET_CONFIG_TEMP	Temporary calibration setup (not saved to flash): { band, channel, correction }
REQ_GPS_RESET	Send GPS reset command: { temp: "hot" | "warm" | "cold" }
REQ_GPS_POWER_ON	Power on GPS module
REQ_GPS_POWER_OFF	Power off GPS module (battery remains on)
REQ_GPS_POWER_OFF	Power off GPS module including battery backup

Build fixes for Debian/Ubuntu (gcc-arm-none-eabi 13.2)

The ext/picoinf submodule required local patches to build on a standard Debian/Ubuntu toolchain. These patches are not upstream — reapply them if you reset or update the submodule. The full patch is committed to the repo as ext/picoinf.patch.

Root causes:

• The packaged gcc-arm-none-eabi uses its own internal stdint.h rather than newlib's, so __int64_t_defined is never set, causing PRIu64/SCNu* macros from newlib's inttypes.h to be undefined even after #include <cinttypes>.
• WsprEncoded unit tests were being compiled and cross-linked with the ARM toolchain (missing POSIX syscalls).
• clock_handle_t was renamed to enum clock_index in the pico-sdk version used here.
• Time.h was renamed to TimeClass.h in picoinf.

Files patched:

File	Change
ext/picoinf/CMakeLists.txt	Add __STDC_FORMAT_MACROS compile definition
ext/picoinf/ext/WsprEncoded/CMakeLists.txt	Suppress -Werror=stringop-truncation; skip test/ subdirectory when not top-level project
ext/picoinf/src/App/Log/Log.cpp	Replace PRIu64/PRId64 with %llu/%lld
ext/picoinf/src/App/Utl/UtlString.h	Add #include <cstdint>
ext/picoinf/src/App/Utl/UtlString.cpp	Replace PRIu64 with %llu
ext/picoinf/src/App/Service/TimeClass.cpp	Replace SCNu* macros with %u and explicit casts
ext/picoinf/src/App/Peripheral/Clock.cpp	Replace clock_handle_t with enum clock_index
ext/picoinf/src/WSPR/WSPRMessageTransmitter.h	Add void Key(bool on) for fast CW keying via output_enable toggle