Add improved HX711 library by Ralf Lindlein

lib/hx711_heisenberg.py

@@ -0,0 +1,105 @@
+# -*- coding: utf-8 -*-
+# (c) 2017-2018 David Gerber <https://github.com/geda>
+# HX711 library for the LoPy.
+# https://github.com/geda/hx711-lopy
+"""
+Updates
+=======
+(c) 2019 Ralf Lindlein <https://github.com/walterheisenberg>
+License: GNU General Public License, Version 3
+https://github.com/walterheisenberg/hivewatch_esp32/blob/master/lib/hx711lib.py
+
+Setup China-Waage
+=================
+::
+
+    sc = HX711(0, 2)
+    sc.set_scale(11.026667)
+    sc.set_offset(130800.0)
+
+    # Offset without wooden board
+    #sc.set_offset(130748.3)
+
+Notes
+=====
+- Some infos about low-pass filters
+  https://microsoft.public.de.excel.narkive.com/PNakkyeu/tiefpassfilter
+
+- The **time constant** means:
+
+    - Lowers value will yield smoother low-pass filtering.
+    - Use 0.9 to get more responsive values, 0.1 (default) means more filtered.
+
+"""
+from hx711 import HX711
+
+
+class HX711Heisenberg(HX711):
+
+    def __init__(self, dout, pd_sck, gain=128):
+        super().__init__(dout, pd_sck, gain)
+
+        self.time_constant = 0.9
+
+    def set_gain(self, gain):
+        if gain is 128:
+            self.GAIN = 1
+        elif gain is 64:
+            self.GAIN = 3
+        elif gain is 32:
+            self.GAIN = 2
+
+        # v1: Skip first reading.
+        #self.read()
+        #self.filtered = self.read()
+
+        # v2: Take average of three readings.
+        # TODO: Maybe improve this.
+        sum = 0
+        for i in range(3):
+            sum += self.read()
+        self.filtered = sum / 3
+
+        print('Gain & initial value set')
+
+    def read_median(self, times=8):
+        """
+        Acquire multiple readings and return median.
+        """
+        lst = []
+        for i in range(times):
+            lst.append(self.read_average())
+        sortedLst = sorted(lst)
+        #print(sortedLst)
+        lstLen = len(lst)
+        index = (lstLen - 1) // 2
+
+        if (lstLen % 2):
+            return sortedLst[index]
+        else:
+            return (sortedLst[index] + sortedLst[index + 1])/2.0
+
+    def get_avgkg(self, times=3):
+        return round(self.get_value(times) / self.SCALE / 1000, 3)
+
+    def get_lpkg(self):
+        self.filtered += self.time_constant * (self.read() - self.filtered)
+        return round((self.filtered - self.OFFSET) / self.SCALE / 1000, 3)
+
+    def get_medkg(self):
+        return round((self.read_median() - self.OFFSET) / self.SCALE / 1000, 3)
+
+    def tare(self, times=15):
+        sum = self.read_average(times)
+        self.set_offset(sum)
+        print('OFFSET = ' + str(sum))
+
+    def set_scale(self, scale=None):
+        if scale is None:
+            return self.SCALE
+        self.SCALE = scale
+
+    def set_offset(self, offset=None):
+        if offset is None:
+            return self.OFFSET
+        self.OFFSET = offset