From 2e630cef014bcc48eb8ae885b25b62a80facaedf Mon Sep 17 00:00:00 2001
From: Tom Keffer <tkeffer>
Date: Sat, 14 Sep 2013 01:23:57 +0000
Subject: [PATCH] For WMR9x8 stations, wind chill is now retrieved from the
 console rather than calculated in software. Thank you user Peter Ferencz!

---
 TODO.txt                    |  2 ++
 bin/weewx/drivers/wmr9x8.py | 22 +++++++++++-----------
 docs/changes.txt            |  6 ++++--
 3 files changed, 17 insertions(+), 13 deletions(-)

diff --git a/TODO.txt b/TODO.txt
index beb84d2e..bab928ba 100644
--- a/TODO.txt
+++ b/TODO.txt
@@ -1,2 +1,4 @@
 TODO before the next release:
 
+Can wind chill be retrieved from the hardware for the WMR918
+(as well as WMR9x8)?
diff --git a/bin/weewx/drivers/wmr9x8.py b/bin/weewx/drivers/wmr9x8.py
index 904609bd..a9ff2772 100644
--- a/bin/weewx/drivers/wmr9x8.py
+++ b/bin/weewx/drivers/wmr9x8.py
@@ -244,8 +244,17 @@ class WMR9x8(weewx.abstractstation.AbstractStation):
         windGustSpeed = ((gust10th/10.0) + gust1 + (gust10*10)) * 3.6
         if windGustSpeed >= _record['windSpeed']:
             _record['windGust'] = windGustSpeed
-        # Save the wind record to be used for windchill and heat index
-        self.last_wind_record = _record
+
+        # Bit 1 of chillstatus is on if there is no wind chill data;
+        # Bit 2 is on if it has overflowed. Check them both:
+        if chillstatus & 0x6 == 0:
+            chill = chill1 + (10*chill10)
+            if chillstatus & 0x8:
+                chill = -chill
+            _record['windchill'] = chill
+        else:
+            _record['windchill'] = None
+        
         return _record
 
     @wmr9x8_registerpackettype(typecode=0x01, size=16)
@@ -297,15 +306,6 @@ class WMR9x8(weewx.abstractstation.AbstractStation):
                 _record['dewpoint']  = dew
             if dewunder and not tempoverunder:
                 _record['dewpoint']  = weewx.wxformulas.dewpointC(temp, hum)
-            # The WMR does not provide wind information in a temperature packet,
-            # so we have to use old wind data to calculate wind chill, provided
-            # it isn't too old and has gone stale. If no wind data has been seen
-            # yet, then this will raise an AttributeError exception.
-            try:
-                if _record['dateTime'] - self.last_wind_record['dateTime'] <= self.stale_wind:
-                    _record['windchill'] = weewx.wxformulas.windchillC(temp, self.last_wind_record['windSpeed'])
-            except AttributeError:
-                pass
         else:
             # If additional temperature sensors exist (channel>=2), then
             # use observation types 'extraTemp1', 'extraTemp2', etc.
diff --git a/docs/changes.txt b/docs/changes.txt
index f3526715..08f9d92a 100644
--- a/docs/changes.txt
+++ b/docs/changes.txt
@@ -8,12 +8,14 @@ In particular, set the environment variable LANG to your locale, and
 then weewx date and number formatting will follow local conventions.
 Details in a new section in the Customization Guide.
 
-Added aggregate type "minmax" and "maxmin", thanks to user Gary Roderick.
-Thanks, Gary!
+Added aggregate type "minmax" and "maxmin". Thank you user Gary Roderick!
 
 WMR100, Vantage, FineOffset, and WS28xx drivers now emit a null wind
 direction when the wind speed is zero.
 
+For WMR9x8 stations, wind chill is now retrieved from the console
+rather than calculated in software. Thank you user Peter Ferencz!
+
 The LOOP value for daily ET on Vantages was too high by a factor of 10. 
 This has been corrected.