def __init__(self, dispatcher, devname):
"Constructor. devname - serial port devname"
self.dispatcher = dispatcher
self.stream = RCSerialStream(devname)
self._next_pkt_id = 0
class Host(object):
"Interface to the hardware"
def __init__(self, dispatcher, devname):
"Constructor. devname - serial port devname"
self.dispatcher = dispatcher
self.stream = RCSerialStream(devname)
self._next_pkt_id = 0
def send_raw(self, buf):
"Send raw data without any checksuming and headers"
#print "Sending: %s" % (", ".join(["0x%02x" % a for a in buf]))
buf = ''.join([chr(a) for a in buf])
with self.stream.get_writer() as writer:
writer.write_bytes(buf)
writer.flush()
def flush(self):
self.stream.flush()
def send(self, pkt):
"Immediately pushes packet to the serial port"
buf = [0x5a]
_crc = 0
for data in [len(pkt)] + list(pkt):
if type(data) == str and len(data) == 1:
data = ord(data)
_crc = crc(_crc, data)
buf.append(data)
buf.append(_crc)
self.send_raw(buf)
def loop(self):
"Infinitely reads serial input and parses packets"
with self.stream.get_reader() as reader:
while True:
# waiting for preamble
while True:
data = ord(reader.read_bytes(1))
if data == 0x5a:
break
# reading packet length
_crc = 0
pktlen = ord(reader.read_bytes(1))
_crc = crc(_crc, pktlen)
# reading packet data
if pktlen > 0:
data = []
for d in reader.read_bytes(pktlen):
d = ord(d)
data.append(d)
_crc = crc(_crc, d)
# reading CRC
_crc = crc(_crc, ord(reader.read_bytes(1)))
# checking CRC
if _crc == 0:
#print "Packet received successfully: %s" % (", ".join(["0x%02x" % d for d in data]))
self.dispatcher.receive(data)
def available(self):
"Check whether host is available"
req = HostEchoRequest()
try:
return self.dispatcher.request(req, timeout=3)
except TimeoutError:
return False
def calibrate_baudrate(self):
"Perform baud rate calibration"
req = BaudRateCalibrationRequest()
try:
return self.dispatcher.request(req, timeout=3)
except TimeoutError:
raise BaudRateCalibrationError()
def next_pkt_id(self):
self._next_pkt_id = (self._next_pkt_id + 1) % 256
return self._next_pkt_id
