def __unpack_header(self, data):
pay_len = len(data) - 4
ncmd, length, cmd_data = struct.unpack('!bb%ds' % pay_len,
check_crc(data))
if pay_len != length:
raise LengthError("Wrong command length")
return ncmd, length, cmd_data
def __unpack_header(self, data):
pay_len = len(data) - 4
ncmd, length, cmd_data = struct.unpack('!bb%ds' % pay_len,
check_crc(data))
if pay_len != length:
raise LengthError("Wrong command length")
return ncmd, length, cmd_data
def test_check_crc(self):
packets = [
bytearray([0x00, 0x61, 0x61]),
bytearray([0x02, 0xbc, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67]),
]
for packet in packets:
assert check_crc(packet) == packet[2:]
self.assertRaises(CRCError, check_crc, bytearray([0x00, 0x61, 0x62]))
def send_command(self, cmd, ret_fmt):
"""Build a command packet, send it to the openDAQ and process the
response
Args:
cmd: Command ID
ret_fmt: Payload format using python 'struct' format characters
Returns:
Command ID and arguments of the response
Raises:
LengthError: The legth of the response is not the expected
"""
if self.measuring:
self.stop()
# Add 'command' and 'length' fields to the format string
fmt = '!BB' + ret_fmt
ret_len = 2 + struct.calcsize(fmt)
packet = crc(cmd) + cmd
self.ser.write(packet)
ret = self.ser.read(ret_len)
if self.debug:
print 'Command: ',
for c in packet:
print '%02X' % ord(c),
print
print 'Response: ',
for c in ret:
print '%02X' % ord(c),
print
if ret == NAK:
raise IOError("NAK response received")
data = struct.unpack(fmt, check_crc(ret))
if len(ret) != ret_len:
raise LengthError("Bad packet length %d (it should be %d)" %
(len(ret), ret_len))
if data[1] != ret_len-4:
raise LengthError("Bad body length %d (it should be %d)" %
(ret_len-4, data[1]))
# Strip 'command' and 'length' values from returned data
return data[2:]
def send_command(self, command, ret_fmt):
"""Build a command packet, send it to the openDAQ and process the
response
Args:
cmd: Command string
ret_fmt: Payload format of the response using python
'struct' format characters
Returns:
Command ID and arguments of the response
Raises:
LengthError: The legth of the response is not the expected
"""
fmt = '!BB' + ret_fmt
ret_len = 2 + struct.calcsize(fmt)
self.ser.write(command)
ret = self.ser.read(ret_len)
if self.debug:
print 'Command: ',
for c in command:
print '%02X' % ord(c),
print
print 'Response: ',
for c in ret:
print '%02X' % ord(c),
print
if ret == NAK:
raise IOError("NAK response received")
data = struct.unpack(fmt, check_crc(ret))
if len(ret) != ret_len:
raise LengthError("Bad packet length %d (it should be %d)" %
(len(ret), ret_len))
if data[1] != ret_len - 4:
raise LengthError("Bad body length %d (it should be %d)" %
(ret_len - 4, data[1]))
# Strip 'command' and 'length' values from returned data
return data[2:]
def test_check_crc(self):
assert check_crc('\x00\x61' + 'a') == 'a'
assert check_crc('\x02\xbc' + 'abcdefg') == 'abcdefg'
self.assertRaises(CRCError, check_crc, '\x00a' + 'b')
def test_check_crc(self):
assert check_crc('\x00\x61' + 'a') == 'a'
assert check_crc('\x02\xbc' + 'abcdefg') == 'abcdefg'
self.assertRaises(CRCError, check_crc, '\x00a' + 'b')
