Fri3d Camp 2024 Badge: improve battery monitor calibration

ThomasFarstrike · ThomasFarstrike · commit 60b68efd7972 · 2025-11-24T22:07:18.000+01:00
diff --git a/internal_filesystem/lib/mpos/battery_voltage.py b/internal_filesystem/lib/mpos/battery_voltage.py
@@ -4,7 +4,7 @@
 MAX_VOLTAGE = 4.15
 
 adc = None
-scale_factor = 0
+conversion_func = None  # Conversion function: ADC value -> voltage
 adc_pin = None
 
 # Cache to reduce WiFi interruptions (ADC2 requires WiFi to be disabled)
@@ -19,7 +19,7 @@ def _is_adc2_pin(pin):
     return 11 <= pin <= 20
 
 
-def init_adc(pinnr, sf):
+def init_adc(pinnr, adc_to_voltage_func):
     """
     Initialize ADC for battery voltage monitoring.
 
@@ -29,13 +29,16 @@ def init_adc(pinnr, sf):
 
     Args:
         pinnr: GPIO pin number
-        sf: Scale factor to convert raw ADC (0-4095) to battery voltage
+        adc_to_voltage_func: Conversion function that takes raw ADC value (0-4095)
+                             and returns battery voltage in volts
     """
-    global adc, scale_factor, adc_pin
-    scale_factor = sf
+    global adc, conversion_func, adc_pin
+
+    conversion_func = adc_to_voltage_func
     adc_pin = pinnr
+
     try:
-        print(f"Initializing ADC pin {pinnr} with scale_factor {sf}")
+        print(f"Initializing ADC pin {pinnr} with conversion function")
         if _is_adc2_pin(pinnr):
             print(f"  WARNING: GPIO{pinnr} is on ADC2 - WiFi will be disabled during readings")
         from machine import ADC, Pin
@@ -44,6 +47,9 @@ def init_adc(pinnr, sf):
     except Exception as e:
         print(f"Info: this platform has no ADC for measuring battery voltage: {e}")
 
+    initial_adc_value = read_raw_adc()
+    print("Reading ADC at init to fill cache: {initial_adc_value} => {read_battery_voltage(raw_adc_value=initial_adc_value)}V => {get_battery_percentage(raw_adc_value=initial_adc_value)}%")
+
 
 def read_raw_adc(force_refresh=False):
     """
@@ -63,12 +69,10 @@ def read_raw_adc(force_refresh=False):
     """
     global _cached_raw_adc, _last_read_time
 
-    # Desktop mode - return random value
+    # Desktop mode - return random value in typical ADC range
     if not adc:
         import random
-        return random.randint(1900, 2600) if scale_factor == 0 else random.randint(
-            int(MIN_VOLTAGE / scale_factor), int(MAX_VOLTAGE / scale_factor)
-        )
+        return random.randint(1900, 2600)
 
     # Check if this is an ADC2 pin (requires WiFi disable)
     needs_wifi_disable = adc_pin is not None and _is_adc2_pin(adc_pin)
@@ -115,7 +119,7 @@ def read_raw_adc(force_refresh=False):
             WifiService.temporarily_enable(was_connected)
 
 
-def read_battery_voltage(force_refresh=False):
+def read_battery_voltage(force_refresh=False, raw_adc_value=None):
     """
     Read battery voltage in volts.
 
@@ -125,19 +129,19 @@ def read_battery_voltage(force_refresh=False):
     Returns:
         float: Battery voltage in volts (clamped to 0-MAX_VOLTAGE)
     """
-    raw = read_raw_adc(force_refresh)
-    voltage = raw * scale_factor
+    raw = raw_adc_value if raw_adc_value else read_raw_adc(force_refresh)
+    voltage = conversion_func(raw) if conversion_func else 0.0
     return max(0.0, min(voltage, MAX_VOLTAGE))
 
 
-def get_battery_percentage():
+def get_battery_percentage(raw_adc_value=None):
     """
     Get battery charge percentage.
 
     Returns:
         float: Battery percentage (0-100)
     """
-    voltage = read_battery_voltage()
+    voltage = read_battery_voltage(raw_adc_value=raw_adc_value)
     percentage = (voltage - MIN_VOLTAGE) * 100.0 / (MAX_VOLTAGE - MIN_VOLTAGE)
     return max(0.0, min(100.0, percentage))
 
diff --git a/internal_filesystem/lib/mpos/board/fri3d_2024.py b/internal_filesystem/lib/mpos/board/fri3d_2024.py
@@ -275,9 +275,14 @@ def keypad_read_cb(indev, data):
 2269 is 3.831
 """
 def adc_to_voltage(adc_value):
+    """
+    Convert raw ADC value to battery voltage using calibrated linear function.
+    Calibration data shows linear relationship: voltage = -0.0016237 * adc + 8.2035
+    This is ~10x more accurate than simple scaling (error ~0.01V vs ~0.1V).
+    """
     return (-0.0016237 * adc_value + 8.2035)
-#mpos.battery_voltage.init_adc(13, adc_to_voltage)
-mpos.battery_voltage.init_adc(13, 1/616) # simple scaling has an error of ~0.01V vs the adc_to_voltage() method
+
+mpos.battery_voltage.init_adc(13, adc_to_voltage)
 
 import mpos.sdcard
 mpos.sdcard.init(spi_bus, cs_pin=14)
diff --git a/internal_filesystem/lib/mpos/board/linux.py b/internal_filesystem/lib/mpos/board/linux.py
@@ -88,7 +88,12 @@ def catch_escape_key(indev, indev_data):
 
 # Simulated battery voltage ADC measuring
 import mpos.battery_voltage
-mpos.battery_voltage.init_adc(999, (3.3 / 4095) * 2)
+
+def adc_to_voltage(adc_value):
+    """Convert simulated ADC value to voltage."""
+    return adc_value * (3.3 / 4095) * 2
+
+mpos.battery_voltage.init_adc(999, adc_to_voltage)
 
 print("linux.py finished")
 
diff --git a/internal_filesystem/lib/mpos/board/waveshare_esp32_s3_touch_lcd_2.py b/internal_filesystem/lib/mpos/board/waveshare_esp32_s3_touch_lcd_2.py
@@ -81,7 +81,19 @@
 
 # Battery voltage ADC measuring
 import mpos.battery_voltage
-mpos.battery_voltage.init_adc(5, 262 / 100000)
+
+def adc_to_voltage(adc_value):
+    """
+    Convert raw ADC value to battery voltage.
+    Currently uses simple linear scaling: voltage = adc * 0.00262
+
+    This could be improved with calibration data similar to Fri3d board.
+    To calibrate: measure actual battery voltages and corresponding ADC readings,
+    then fit a linear or polynomial function.
+    """
+    return adc_value * 0.00262
+
+mpos.battery_voltage.init_adc(5, adc_to_voltage)
 
 # On the Waveshare ESP32-S3-Touch-LCD-2, the camera is hard-wired to power on,
 # so it needs a software power off to prevent it from staying hot all the time and quickly draining the battery.
diff --git a/internal_filesystem/lib/mpos/ui/topmenu.py b/internal_filesystem/lib/mpos/ui/topmenu.py
@@ -154,6 +154,7 @@ def update_battery_icon(timer=None):
         # Percentage is not shown for now:
         #battery_label.set_text(f"{round(percent)}%")
         #battery_label.remove_flag(lv.obj.FLAG.HIDDEN)
+    update_battery_icon() # run it immediately instead of waiting for the timer
 
     def update_wifi_icon(timer):
         from mpos.net.wifi_service import WifiService
