From 5665ccff52319a80a0ede6db5f85a37929d06af0 Mon Sep 17 00:00:00 2001
From: Pierrick C <arofarn@arofarn.info>
Date: Thu, 2 Aug 2018 00:11:57 +0200
Subject: [PATCH] Add function to measure Vbat with some simple filter (mean of
 n samples, 10 by default)

---
 circuitpython/main.py | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/circuitpython/main.py b/circuitpython/main.py
index a0660f5..de15027 100644
--- a/circuitpython/main.py
+++ b/circuitpython/main.py
@@ -68,15 +68,10 @@ class Data:
         #Data from Feather board
         self.data['SYS'] = {'time': {'val': datetime_format.format(*clock.datetime[0:6]),
                                      'unit': '' },
-                            'v_bat': {'val': vbat.value*0.000100708,
+                            'v_bat': {'val': measure_vbat(),
                                       'unit': 'V' },
                             'CPU_temp': {'val': microcontroller.cpu.temperature,
                                          'unit': '°C' }}
-        # Note about v_bat calculation :
-        # 0.000100708 = 2*3.3/65536 with
-        #  2 : voltage is divided by 2
-        #  3.3 : Vref = 3.3V
-        #  65536 : 16bit ADC
 
         #Data from BME280
         self.data['BME280'] = {'temp': { 'val': round(bme280.temperature, 1), 'unit': '°C' },
@@ -197,6 +192,20 @@ def set_clock_from_GPS():
             clock.datetime = gps_datetime   #Trust GPS if there is a bias
             print("New date/time : " + datetime_format.format(*clock.datetime[0:6]))
 
+def measure_vbat(samples=10, timestep=0.01):
+    """Measure Vbattery as the mean of n samples with timestep second between
+    each measurement"""
+    # Note about v_bat calculation :
+    # 0.000100708 = 2*3.3/65536 with
+    #  2 : voltage is divided by 2
+    #  3.3 : Vref = 3.3V
+    #  65536 : 16bit ADC
+    v = 0
+    for i in range(samples):
+        v = v + vbat.value
+        time.sleep(timestep)
+    return v/samples*0.000100708
+
 #########
 # Setup #
 #########