Add battery capacity to python API

Documentation/pycardium/power.rst

@@ -32,6 +32,13 @@ in your scripts.
 
    .. versionadded:: 1.4
 
+.. py:function:: read_battery_capacity()
+
+   Calculate the remaining battery capacity in percent.
+
+   Uses 42 logarithmic values from a look-up table to estimate
+   the remaining capacity in percent based on the battery voltage.
+
 .. py:function:: read_chargein_voltage()
 
    Read the charge voltage in V.

pycardium/modules/power.c

@@ -32,6 +32,20 @@ static MP_DEFINE_CONST_FUN_OBJ_0(
 	power_read_battery_current_obj, mp_power_read_battery_current
 );
 
+static mp_obj_t mp_power_read_battery_capacity()
+{
+    float result;
+    int status = epic_read_battery_capacity(&result);
+    if (status < 0) {
+        mp_raise_OSError(-status);
+        return mp_const_none;
+    }
+    return mp_obj_new_float(result);
+}
+static MP_DEFINE_CONST_FUN_OBJ_0(
+    power_read_battery_capacity_obj, mp_power_read_battery_capacity
+);
+
 static mp_obj_t mp_power_read_chargein_voltage()
 {
 	float result;
@@ -94,7 +108,9 @@ static const mp_rom_map_elem_t power_module_globals_table[] = {
 	  MP_ROM_PTR(&power_read_battery_voltage_obj) },
 	{ MP_ROM_QSTR(MP_QSTR_read_battery_current),
 	  MP_ROM_PTR(&power_read_battery_current_obj) },
-	{ MP_ROM_QSTR(MP_QSTR_read_chargein_voltage),
+    { MP_ROM_QSTR(MP_QSTR_read_battery_capacity),
+      MP_ROM_PTR(&power_read_battery_capacity_obj) },
+    { MP_ROM_QSTR(MP_QSTR_read_chargein_voltage),
 	  MP_ROM_PTR(&power_read_chargein_voltage_obj) },
 	{ MP_ROM_QSTR(MP_QSTR_read_chargein_current),
 	  MP_ROM_PTR(&power_read_chargein_current_obj) },

pycardium/modules/qstrdefs.h

@@ -76,6 +76,7 @@ Q(z)
 Q(power)
 Q(read_battery_voltage)
 Q(read_battery_current)
+Q(read_battery_capacity)
 Q(read_chargein_voltage)
 Q(read_chargein_current)
 Q(read_system_voltage)