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#!/bin/bash

# gps_diag.sh

# One-shot GPS diagnostic: answers "is the receiver actually getting a fix, or is

# Ragnar failing to parse one?" — the two causes of a permanent "Searching...".

# It briefly stops ragnar/gpsd to read the raw serial port (nothing else can hold

# it open while we sample), captures ~10 s of NMEA, then restarts ragnar. Output

# is deliberately compact so it can be pasted into a chat/issue without the

# terminal pager chopping lines.

# Usage: sudo bash scripts/gps_diag.sh

# Reading the result:

# * GGA fix quality >= 1, or RMC status 'A' -> the receiver HAS a fix. If

# Ragnar still shows "Searching", that is a parsing/plumbing bug worth

# reporting with this output attached.

# * GGA fix quality 0, or RMC status 'V' -> the receiver has NO fix. That

# is antenna/sky view, not software: a cold start needs a clear view of the

# sky and can take several minutes.

# * No sentences at all -> wrong device, wrong baud, or

# something else is holding the port.

set -u

SECONDS_TO_SAMPLE="${1:-10}"

RAW=/tmp/ragnar_nmea.raw

OUT=/tmp/ragnar_gpsdiag.txt

if [ "$(id -u)" -ne 0 ]; then

echo "Run with sudo: sudo bash scripts/gps_diag.sh" >&2

exit 1

# Pick the GPS device: prefer an explicit arg, else the first tty that is not an

# Espressif companion (a Piglet/Huginn ESP32 also shows up as /dev/ttyACM*).

pick_device() {

for dev in /dev/ttyACM* /dev/ttyUSB*; do

[ -e "$dev" ] || continue

# Skip Espressif VID (303a) — that's a companion board, not a GPS.

if udevadm info -q property -n "$dev" 2>/dev/null | grep -qi 'ID_VENDOR_ID=303a'; then

continue

echo "$dev"

return

done

}

GPSDEV="${GPSDEV:-$(pick_device)}"

# What IS this device? A silent /dev/ttyACM0 is very often not a GPS at all —

# an ESP32 companion, an LTE modem, or an Arduino enumerate the same way.

describe_device() {

local dev="$1"

[ -n "$dev" ] || return

udevadm info -q property -n "$dev" 2>/dev/null | grep -E \

| sed 's/^/ /'

}

# Who is holding the port open? Anything still attached explains total silence.

port_holders() {

local dev="$1"

[ -n "$dev" ] || return

if command -v fuser >/dev/null 2>&1; then

fuser -v "$dev" 2>&1 | sed 's/^/ /' | head -8

elif command -v lsof >/dev/null 2>&1; then

lsof "$dev" 2>/dev/null | sed 's/^/ /' | head -8

else

echo " (install psmisc or lsof to check)"

}

# Stop anything holding the serial port, sample, then bring ragnar back up.

systemctl stop ragnar >/dev/null 2>&1

systemctl stop gpsd.socket gpsd >/dev/null 2>&1

sleep 1

: > "$RAW"

# Probe across the common GPS baud rates and keep the best capture. On a CDC-ACM

# device baud is usually a no-op, but ttyUSB bridges (FTDI/PL2303/CP210x) care,

# and a mismatch yields either silence or binary garbage. We score by NMEA

# sentences found, falling back to raw byte count so a receiver stuck in u-blox

# UBX *binary* mode still registers as "talking" — counting lines alone reports

# a chatty binary stream as "0 lines", which is what sent us down this path.

BEST_BAUD=""

BEST_NMEA=0

BEST_BYTES=0

BAUD_REPORT=""

if [ -n "${GPSDEV:-}" ]; then

for baud in 9600 4800 38400 57600 115200; do

stty -F "$GPSDEV" "$baud" raw -echo -crtscts 2>/dev/null || true

tmp=$(mktemp)

timeout 3 cat "$GPSDEV" > "$tmp" 2>/dev/null || true

bytes=$(wc -c < "$tmp" | tr -d ' ')

nmea=$(grep -ac '^\$G' "$tmp" 2>/dev/null || true); nmea=${nmea:-0}

BAUD_REPORT="${BAUD_REPORT} ${baud}: ${bytes} bytes, ${nmea} NMEA sentences\n"

if [ "$nmea" -gt "$BEST_NMEA" ] 2>/dev/null || \

{ [ "$BEST_NMEA" -eq 0 ] 2>/dev/null && [ "$bytes" -gt "$BEST_BYTES" ] 2>/dev/null; }; then

BEST_BAUD="$baud"; BEST_NMEA="$nmea"; BEST_BYTES="$bytes"

cp "$tmp" "$RAW"

rm -f "$tmp"

done

# Longer capture at whichever baud looked best, for the fix verdict.

if [ "$BEST_NMEA" -gt 0 ] 2>/dev/null; then

stty -F "$GPSDEV" "$BEST_BAUD" raw -echo -crtscts 2>/dev/null || true

timeout "$SECONDS_TO_SAMPLE" cat "$GPSDEV" > "$RAW" 2>/dev/null || true

systemctl start ragnar >/dev/null 2>&1

{

echo "=== Ragnar GPS diagnostic ==="

echo "commit : $(git -C "$(dirname "$0")/.." log --oneline -1 2>/dev/null || echo unknown)"

echo "gps device: ${GPSDEV:-NONE FOUND}"

echo "tty list : $(ls /dev/ttyACM* /dev/ttyUSB* 2>/dev/null | tr '\n' ' ' || echo none)"

echo "sampled : $(wc -c < "$RAW" | tr -d ' ') bytes, $(wc -l < "$RAW") lines"

echo "--- device identity ---"

describe_device "${GPSDEV:-}"

echo

echo "--- baud probe (bytes / NMEA sentences per rate) ---"

printf "%b" "${BAUD_REPORT:- (no device probed)\n}"

echo

if [ ! -s "$RAW" ]; then

echo "NO DATA on ${GPSDEV:-<no device>} at any baud rate — the port is"

echo "open but the device sends nothing at all."

echo

echo "--- who is holding the port ---"

port_holders "${GPSDEV:-}"

echo

echo "Most likely, in order:"

echo " 1. This is NOT a GPS. Check 'device identity' above — an ESP32"

echo " companion, LTE modem or Arduino also enumerates as ttyACM0."

echo " A u-blox/GPS puck usually names itself in ID_VENDOR/ID_MODEL."

echo " 2. The receiver has no power / no antenna connection. Many pucks"

echo " show a blinking LED only once they are transmitting."

echo " 3. It needs DTR asserted before it will talk. Test with:"

echo " sudo stty -F ${GPSDEV:-/dev/ttyACM0} 9600 raw -echo"

echo " sudo cat ${GPSDEV:-/dev/ttyACM0}"

echo " 4. Wrong tty — if several are listed above, retry pinning one:"

echo " sudo GPSDEV=/dev/ttyUSB0 bash scripts/gps_diag.sh"

exit 0

# Bytes arrived but no NMEA: binary mode or wrong baud. Show the raw bytes —

# UBX frames start b5 62, garbage looks like random high bytes.

if [ "$BEST_NMEA" -eq 0 ] 2>/dev/null; then

echo "DATA IS ARRIVING (${BEST_BYTES} bytes at ${BEST_BAUD} baud) BUT NO NMEA."

echo

echo "--- first bytes (hex) ---"

head -c 128 "$RAW" | od -A x -t x1z | head -8

echo

echo "If frames start with 'b5 62' the receiver is in u-blox UBX BINARY"

echo "mode and must be switched to NMEA (u-center, or a UBX-CFG-PRT"

echo "message). If the bytes look random, the baud rate is wrong."

exit 0

echo "--- sentence types seen ---"

awk -F, '/^\$/ {print $1}' "$RAW" | sort | uniq -c | sort -rn | head -12

echo

echo "--- sample GGA (field 6 = fix quality: 0=no fix, 1=GPS, 2=DGPS) ---"

grep -m3 'GGA' "$RAW" || echo "(no GGA sentences)"

echo

echo "--- sample RMC (field 2 = status: A=valid fix, V=void) ---"

grep -m3 'RMC' "$RAW" || echo "(no RMC sentences)"

echo

# Machine-readable verdict so the answer doesn't depend on eyeballing fields.

gga_fix=$(awk -F, '/GGA/ && $7 ~ /^[0-9]+$/ {if ($7+0 > m) m=$7+0} END {print m+0}' "$RAW")

# grep -c exits 1 when the count is 0, so guard with `|| true` rather than a

# `|| echo 0` fallback — the latter appends a second line to the count.

rmc_a=$(grep -c 'RMC,[^,]*,A,' "$RAW" 2>/dev/null || true)

rmc_a=${rmc_a:-0}

echo "--- verdict ---"

echo "best GGA fix quality : $gga_fix"

echo "RMC sentences w/ 'A' : $rmc_a"

if [ "$gga_fix" -ge 1 ] 2>/dev/null || [ "$rmc_a" -ge 1 ] 2>/dev/null; then

echo "RECEIVER HAS A FIX. If Ragnar still shows 'Searching', it is a"

echo "software/parsing issue — report this output."

else

echo "RECEIVER HAS NO FIX (searching). This is antenna / sky view, not"

echo "software. Give it a clear view of the sky; a cold start can take"

echo "several minutes."

} 2>&1 | tee "$OUT"

echo

echo "Saved to $OUT — paste that file's contents to share the result."

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