primozcigler · December 19, 2020 21:46 · Dec 19, 2020
diff --git a/libela-elsi-g-325-weight.py b/libela-elsi-g-325-weight.py
@@ -0,0 +1,77 @@
+import serial
+
+"""
+Tehtnica: Libela Elsi G 325 (https://www.libela-elsi.si/en/retail-scales/retail-scales-without-printer/)
+Protokol: TISA-4 (0)
+
+https://pypi.org/project/pyserial/
+https://pyserial.readthedocs.io/en/latest/shortintro.html
+
+Podatki za povezavo s tehtnice: 9600 8 N 1
+baudrate = 9600
+bytesize = 8
+partiy = N
+stopbits = 1
+"""
+
+PORT = '/dev/cu.UC-232AC'
+
+def checksum(bytes_string):
+  """
+  https://stackoverflow.com/questions/26517869/creating-xor-checksum-of-all-bytes-in-hex-string-in-python
+  """
+  cs = 0
+
+  for el in bytes_string:
+    cs ^= el
+
+  return bytes([cs])
+
+def fixed_5_bytes_price(price_as_string):
+  price = round(float(price_as_string), 2)
+
+  decimals = str(round(price % 1, 2))[2:4].encode()
+  integers = str(int(price))[0:3].encode()
+
+  return integers.rjust(3, b'0') + decimals.ljust(2, b'0')
+
+def prepare_outgoing_data():
+  start = b'98'
+
+  price = input("Vpiši ceno izdelka (npr '4.2' za 4,2 €/kg): ")
+  price = fixed_5_bytes_price(price) # '4.2' -> b'00420'
+
+  cs = checksum(start + price)
+
+  return start + price + cs + b'\x0D\x0A'
+
+def display_incoming_data(in_data):
+  data_str = in_data.decode()
+
+  s = "Masa v mirovanju: {}".format("DA" if data_str[2] == "0" else "NE")
+  w = "Izmerjena masa: {:.3f} kg".format(int(data_str[3:8]) / 1000)
+  e = "Znesek OK: {}".format("DA" if data_str[8] == "0" else "NE")
+  i = "Znesek: {:.2f} €".format(int(data_str[9:15]) / 100)
+
+  print(s, w, e, i, sep = "\n")
+
+
+# init
+pos_to_weight = prepare_outgoing_data()
+# print(pos_to_weight)
+
+# open serial port
+ser = serial.Serial(PORT, timeout = 1, write_timeout = 1)
+
+# print data on the just created and opened serial device
+# print(ser)
+
+# send data
+ser.write(pos_to_weight)
+
+response = ser.read_until(b'\r\n')
+#print(response)
+display_incoming_data(response)
+
+# close the connection
+ser.close()