89 lines
1.9 KiB
Python
89 lines
1.9 KiB
Python
import serial
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import binascii
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import struct
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import numpy
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class ProtocolError(Exception):
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pass
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class BedditConnection(object):
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def __init__(self, connection):
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self.connection = connection
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def open_connection(self):
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self.connection.write("OK\n")
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response_to_ok = self.connection.readline()
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if response_to_ok != 'OK\n':
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raise ProtocolError("Got {} after OK".format(repr(response_to_ok)))
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def start_streaming(self):
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self.connection.write("START\n")
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def stop_streaming(self):
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self.connection.write("STOP\n")
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def disconnect(self):
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self.connection.close()
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def _read_packet(self):
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header = self.connection.read(6)
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if len(header) != 6:
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raise ProtocolError()
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packet_number = struct.unpack('I', header[:4])[0]
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payload_length = struct.unpack('H', header[4:])[0]
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payload = self.connection.read(payload_length)
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crc = struct.unpack('I', self.connection.read(4))[0]
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computed_crc = binascii.crc32(header + payload) & 0xffffffff
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if crc != computed_crc:
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raise ProtocolError("Invalid CRC")
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return packet_number, payload
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def read_sample_packet(self):
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packet_number, payload = self._read_packet()
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sample_array = numpy.fromstring(payload, "uint16")
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channel1 = sample_array[0::2]
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channel2 = sample_array[1::2]
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return (packet_number, channel1, channel2)
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def main():
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device = '/dev/cu.Beddit3222-BedditSensor'
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ser = serial.Serial()
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ser.port = device
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ser.open()
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conn = BedditConnection(ser)
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try:
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conn.open_connection()
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conn.start_streaming()
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while True:
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packet_number, channel1, channel2 = conn.read_sample_packet()
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for i in channel1:
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print i
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finally:
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conn.stop_streaming()
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conn.disconnect()
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if __name__ == "__main__":
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main()
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