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Sample code for serial (RS-232) connection between computer and Libela Elsi G 325 retail scale/weight
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()
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