iMet-1/4 XDATA decoding, add initial detection of iMet1 vs iMet4 sondes.

auto_rx/auto_rx.py

@@ -497,7 +497,7 @@ def telemetry_filter(telemetry):
     if "sats" in telemetry:
         if telemetry["sats"] < 4:
             logging.warning(
-                "Sonde %s can only see %d SVs - discarding position as bad."
+                "Sonde %s can only see %d GNSS sats - discarding position as bad."
                 % (telemetry["id"], telemetry["sats"])
             )
             return False

auto_rx/autorx/__init__.py

@@ -17,7 +17,7 @@
 # MINOR - New sonde type support, other fairly big changes that may result in telemetry or config file incompatability issus.
 # PATCH - Small changes, or minor feature additions.
 
-__version__ = "1.5.8"
+__version__ = "1.5.9-beta1"
 
 
 # Global Variables

auto_rx/autorx/decode.py

@@ -209,6 +209,12 @@ def __init__(
         # This should hopefully handle a few iMets on the same frequency in a graceful manner.
         self.imet_max_ids = 4
         self.imet_id = []
+        # iMet-1 and iMet-4 sondes behave differently.
+        # iMet-1 sondes increment the frame counter *twice* each second, imet-4 only once per second.
+        # We need to detect this to be able to calculate a start time, and hence generate a serial number.
+        self.imet_type = None
+        self.imet_prev_time = None
+        self.imet_prev_frame = None
 
         # This will become our decoder thread.
         self.decoder = None
@@ -1307,7 +1313,7 @@ def handle_decoder_line(self, data):
             # We append -Ozone to the sonde type field to indicate this.
             # TODO: Decode device ID from aux field to indicate what the aux payload actually is?
             if "aux" in _telemetry:
-                _telemetry["type"] += "-Ozone"
+               _telemetry["type"] += "-Ozone"
 
             # iMet Specific actions
             if self.sonde_type == "IMET":
@@ -1321,9 +1327,44 @@ def handle_decoder_line(self, data):
                 # Fix up the time.
                 _telemetry["datetime_dt"] = fix_datetime(_telemetry["datetime"])
 
+
+                # An attempt at detecting iMet-1 vs iMet-4 sondes based on how the frame count increments
+                # compared to the time.
+                # Note that this is going to break horribly if an iMet-1 and an iMet-4 are on the same frequency,
+                # or if there are multiple iMet-4's in the air when this is performed. I don't have a nice
+                # solution to that second problem.
+                # This may also break when running in UDP mode for long periods.
+                if self.imet_type is None:
+                    if self.imet_prev_frame is None:
+                        self.imet_prev_frame = _telemetry['frame']
+                        self.imet_prev_time = _telemetry["datetime_dt"]
+                        self.log_info("Waiting for additional frames to determine iMet type (1 or 4)")
+                        return False
+                    else:
+                        # Calculate and compare frame vs time deltas.
+                        _time_delta = (_telemetry["datetime_dt"] - self.imet_prev_time).total_seconds()
+                        _frame_delta = _telemetry['frame'] - self.imet_prev_frame
+
+                        if _time_delta == _frame_delta//2:
+                            # Frame counter increments at twice the rate of the time counter = iMet-1
+                            self.log_info("iMet sonde is most likely an iMet-1")
+                            self.imet_type = "iMet-1"
+                        elif _time_delta == _frame_delta:
+                            # Frame counter increments at the same rate as the time counter = iMet-4
+                            self.log_info("iMet sonde is most likely an iMet-4")
+                            self.imet_type = "iMet-4"
+                        else:
+                            # Some other case (possibly 2 sondes on the same frequency?)
+                            # Assume iMet-4...
+                            self.log_info("iMet sonde is most likely an iMet-4 (less confidence)")
+                            self.imet_type = "iMet-4"
+                else:
+                    _telemetry['subtype'] = self.imet_type
+
+
                 # Generate a unique ID based on the power-on time and frequency, as iMet sonde telemetry is painful
                 # and doesn't send any ID. 
-                _new_imet_id = imet_unique_id(_telemetry)
+                _new_imet_id = imet_unique_id(_telemetry, imet1=(self.imet_type=="iMet-1"))
 
                 # If we have seen this ID before, keep using it.
                 if _new_imet_id in self.imet_id:

auto_rx/autorx/sonde_specific.py

@@ -51,7 +51,7 @@ def fix_datetime(datetime_str, local_dt_str=None):
 #
 
 
-def imet_unique_id(telemetry, custom="SONDE"):
+def imet_unique_id(telemetry, custom="SONDE", imet1=False):
     """
 	Generate a 'unique' imet radiosonde ID based on the power-on time, frequency, and an optional location code.
 	This requires the following fields be present in the telemetry dict:
@@ -62,8 +62,16 @@ def imet_unique_id(telemetry, custom="SONDE"):
 
     _imet_dt = telemetry["datetime_dt"]
 
+    if imet1:
+        # iMet-1 sondes increment their frame counter TWICE every second, so we need to
+        # compensate for this to be able to determine a power-on time.
+        _frame = telemetry["frame"]//2
+    else:
+        # iMet-4 sondes increment the frame counter once per second.
+        _frame = telemetry["frame"]
+
     # Determine power on time: Current time -  number of frames (one frame per second)
-    _power_on_time = _imet_dt - datetime.timedelta(seconds=telemetry["frame"])
+    _power_on_time = _imet_dt - datetime.timedelta(seconds=_frame)
 
     # Round frequency to the nearest 100 kHz (iMet sondes only have 100 kHz frequency steps)
     _freq = round(telemetry["freq_float"] * 10.0) / 10.0

auto_rx/autorx/sondehub.py

@@ -192,7 +192,10 @@ def reformat_data(self, telemetry):
 
         elif telemetry["type"] == "IMET":
             _output["manufacturer"] = "Intermet Systems"
-            _output["type"] = "iMet-4"
+            if "subtype" in telemetry:
+                _output["type"] = telemetry['subtype']
+            else:
+                _output["type"] = "iMet-4"
             _output["serial"] = telemetry["id"].split("-")[1]
 
         elif telemetry["type"] == "IMET5":