add strict check for header MSB, only toggle the units pin every 2 minutes

Author: brentru

adafruit_dymoscale.py

@@ -133,11 +133,11 @@ def get_scale_data(self):
                 the_byte |= bits[byte_n*8 + bit_n]
             data_bytes[byte_n] = the_byte
         # do some very basic data checking
-        if data_bytes[0] != 3 or data_bytes[1] != 3 or data_bytes[7] != 4:
+        if data_bytes[0] != 3 and data_bytes[0] != 2: # check the MSB (differs between DYMO scale models)
             raise RuntimeError("Bad data capture")
-
-        if data_bytes[8] != 0x1C or data_bytes[9] != 0 or data_bytes[10] \
-        or data_bytes[11] != 0:
+        if data_bytes[1] != 3 or data_bytes[7] != 4 or data_bytes[8] != 0x1C:
+            raise RuntimeError("Bad data capture")
+        if data_bytes[9] != 0 or data_bytes[10] or data_bytes[11] != 0:
             raise RuntimeError("Bad data capture")
         reading = ScaleReading()
         # parse out the data_bytes

examples/dymoscale_simpletest.py

@@ -1,3 +1,4 @@
+import time
 import board
 import digitalio
 import adafruit_dymoscale
@@ -7,13 +8,16 @@
 units_pin.switch_to_output()
 dymo = adafruit_dymoscale.DYMOScale(board.D4, units_pin)
 
+# take a reading of the current time
+time_stamp = time.monotonic()
+
 while True:
     reading = dymo.weight
     text = "{} g".format(reading.weight)
     print(text)
-    # to avoid sleep mode, we'll toggle the units pin.
-    # if we don't want to switch the units on the next read...
-    dymo.toggle_unit_button()
-
-    # if we do want to switch the units on the next read...
-    # dymo.toggle_unit_button(switch_units=True)
+    # to avoid sleep mode, toggle the units pin every 2 mins.
+    if (time.monotonic() - time_stamp) > 120:
+        print('toggling units button...')
+        dymo.toggle_unit_button()
+        # reset the time
+        time_stamp = time.monotonic()