1 files changed, 36 insertions, 0 deletions
diff --git a/wasp/drivers/battery.py b/wasp/drivers/battery.py
new file mode 100644
index 0000000..cc1eafb
--- /dev/null
+++ b/wasp/drivers/battery.py
@@ -0,0 +1,36 @@
+# Generic lithium ion battery driver
+
+from machine import Pin, ADC
+
+class Battery(object):
+    def __init__(self, battery, charging, power=None):
+        self._battery = ADC(battery)
+        self._charging = charging
+        self._power = power
+
+    def charging(self):
+        return self._charging.value() 
+
+    def power(self):
+        if self._power:
+            return self._power.value()
+        return self._charging.value()
+
+    def voltage_mv(self):
+        # Assumes a 50/50 voltage divider and a 3.3v power supply
+        raw = self._battery.read_u16()
+        return (2 * 3300 * raw) // 65535
+
+    def level(self):
+        # This is a trivial battery level estimation approach. It is assumes
+        # the discharge from 4v to 3.5v is roughly linear and 4v is 100% and
+        # that 3.5v is 5%. Below 3.5v the voltage will start to drop pretty
+        # sharply to we will drop from 5% to 0% pretty fast... but we'll
+        # live with that for now.
+        mv = self.voltage_mv()
+        level = ((19 * mv) // 100) - 660
+        if level > 100:
+            return 100
+        if level < 0:
+            return 0
+        return level