moved reference voltage from xbee_api.py. This way we keep

this package dealing with protocol level, without need to know specifics of actual schematics, like Vref.
vpyshnenko · Mar 9, 2013 · f4100f3 · f4100f3
1 parent d6104d2
commit f4100f3
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Showing 2 changed files with 10 additions and 15 deletions.
diff --git a/data_collector.py b/data_collector.py
@@ -25,19 +25,24 @@
 logger = None
 global_lock = lockfile.FileLock(LOCK_FILE)
 
+VREF = 1235 #LM385-1.2
+
 def cleanup():
     if global_lock.is_locked():
         global_lock.release()
 
-
 def usage():
     print """
 %s [-s /dev/ttyUSB0]
 
 -s port -- use serial port <port>. Default is /dev/ttyUSB0
+-c -- output packet log to console
 
 """  % sys.argv[0]
 
+def get_adc_v(pkt, adc_idx):
+    "Retruns ADC value in volts"
+    return float(pkt.get_adc(adc_idx)/pkt.num_samples * VREF / 1024)
 
 def main():
     global logger
@@ -94,9 +99,9 @@ def main():
             pkt = pkt_reader.next()
 
             try:
-                adc0 = float(pkt.get_adc(0))
-                adc1 = float(pkt.get_adc(1))
-                temp_C = tmp36.get_t_from_adc(adc1)
+                adc0 = float(get_adc_v(pkt,0))
+                adc1 = float(get_adc_v(pkt,1))
+                temp_C = tmp36.get_t_from_adc(adc0)
 
                 time_now = time.time()
                 report = 'packet_size={0} adc0={1:.3f} mV adc1={2:.3f} mV T={3:.1f} C'.format(
@@ -118,6 +123,5 @@ def main():
     except serial.SerialException,e:
         print e
 
-
 if __name__ == '__main__':
     main()
diff --git a/xbee_api.py b/xbee_api.py
@@ -5,9 +5,6 @@
 
 logger = logging.getLogger('default')
 
-# Vref = 2500.0  # MCP1525
-Vref = 2048   # LM4040D20  (actually measured 2036.4 mV, 0.5% difference)
-
 # Sample packet:
 # 7e 0 e 83 56 78 3f 0 1 7 0 1 0 3 ff 3 ff 62 
 # 
@@ -116,8 +113,6 @@ def decode_packet(self, frame, length):
             self.d_channels_data = [0 for x in range(0,9)]
             self.a_channels_data = [0 for x in range(0,8)]
 
-            adc_data = [0.0 for x in range(0,8)]
-
             frame_byte = 8
             for n in range(0, self.num_samples):
                 if self.have_d_channels:
@@ -126,14 +121,10 @@ def decode_packet(self, frame, length):
 
                 for adc_idx in range(0, len(self.a_channels_enabled)):
                     if self.a_channels_enabled[adc_idx]:
-                        adc_data[adc_idx] += self.a_data(
+                        self.a_channels_data[adc_idx] += self.a_data(
                             frame[frame_byte], frame[frame_byte+1])
                         frame_byte += 2
 
-            # store ADC channel data in mV
-            for adc_idx in range(0, len(self.a_channels_enabled)):
-                self.a_channels_data[adc_idx] = (
-                    float(adc_data[adc_idx]) / self.num_samples * Vref / 1024)
         except IndexError:
             logger.error('Invalid XBee API frame: "{0}"'.format(frame))