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read_qr_code.py
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import struct
import time
from pimoroni_i2c import PimoroniI2C
# The code reader has the I2C ID of hex 0c, or decimal 12.
TINY_CODE_READER_I2C_ADDRESS = 0x0C
# How long to pause between sensor polls.
TINY_CODE_READER_DELAY = 0.05
TINY_CODE_READER_LENGTH_OFFSET = 0
TINY_CODE_READER_LENGTH_FORMAT = "H"
TINY_CODE_READER_MESSAGE_OFFSET = TINY_CODE_READER_LENGTH_OFFSET + struct.calcsize(TINY_CODE_READER_LENGTH_FORMAT)
TINY_CODE_READER_MESSAGE_SIZE = 254
TINY_CODE_READER_MESSAGE_FORMAT = "B" * TINY_CODE_READER_MESSAGE_SIZE
TINY_CODE_READER_I2C_FORMAT = TINY_CODE_READER_LENGTH_FORMAT + TINY_CODE_READER_MESSAGE_FORMAT
TINY_CODE_READER_I2C_BYTE_COUNT = struct.calcsize(TINY_CODE_READER_I2C_FORMAT)
PINS_BREAKOUT_GARDEN = {"sda": 4, "scl": 5}
i2c = PimoroniI2C(**PINS_BREAKOUT_GARDEN)
def read_qr_code(timeout):
result = None
while timeout > 0.0:
read_data = bytearray(TINY_CODE_READER_I2C_BYTE_COUNT)
try:
i2c.readfrom_into(TINY_CODE_READER_I2C_ADDRESS, read_data)
except Exception as e:
print("Error reading from Tiny Code Reader", e)
return None
message_length, = struct.unpack_from(TINY_CODE_READER_LENGTH_FORMAT, read_data, TINY_CODE_READER_LENGTH_OFFSET)
message_bytes = struct.unpack_from(TINY_CODE_READER_MESSAGE_FORMAT, read_data, TINY_CODE_READER_MESSAGE_OFFSET)
if message_length > 0:
try:
result = bytearray(message_bytes[0:message_length]).decode("utf-8")
break
except:
print("Couldn't decode as UTF 8")
pass
time.sleep(TINY_CODE_READER_DELAY)
timeout -= TINY_CODE_READER_DELAY
return result