battery level reading

shared/q1.py

@@ -4,7 +4,7 @@
 #
 # NOTE: Lots of hardware overlap with Mk4, so see mk4.py too!
 #
-import os, sys, pyb, ckcc, version, glob
+import os, sys, pyb, ckcc, version, glob, uctypes
 
 def init0():
     # called very early
@@ -19,4 +19,47 @@ def init0():
     from scanner import QRScanner
     glob.SCAN = QRScanner()
 
+    # XXX do not ship like this XXX
+    ckcc.vcp_enabled(True)
+    print("REPL enabled")
+
+    try:
+        setup_adc()
+        print('Batt volt: %s' % get_batt_level())
+    except BaseException as exc:
+        sys.print_exception(exc)
+
+def setup_adc():
+    # configure VREF source as internap 2.5v 
+    VREF_LAYOUT = {
+        "CSR": 0 | uctypes.UINT32,
+        "CCR": 4 | uctypes.UINT32,
+    }
+    VREFBUF_CSR = 0x40010030
+
+    vref = uctypes.struct(VREFBUF_CSR, VREF_LAYOUT)
+    vref.CSR = 0x01     # VRS=0, HIZ=0, ENVR=1
+
+    # could delay here until reads back as 0x9 (VRR==1)
+    # but no need 
+
+def get_batt_level():
+    # return voltage from batteries, as a float
+    # - will only work on battery power, else return None
+    try:
+        from machine import ADC, Pin
+    except ImportError:
+        # simulator
+        return 2.99
+
+    if Pin('NOT_BATTERY')() == 1:
+        # not getting power from batteries, so don't know level
+        return None
+
+    adc = ADC(Pin('VIN_SENSE'))
+    avg = sum(adc.read_u16() for i in range(10)) / 10.0
+
+    return round((avg / 65535.0) * 2.5 * 2, 2)
+    
+
 # EOF