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#!/usr/bin/env python
import sys
import serial
PACKETRETRY = 3
MAXDATLEN = 128
CRCPOLY = 0x810
CRCINIT = 0xFFFF
TX_ACKTIMEOUT = 3 #sec
RX_BYTETIMEOUT = 1 #sec
STX_header = 0x02
SOH_header = 0x01
ETB_header = 0x17
ETX_header = 0x03
ACK_header = 0x06
NAK_header = 0x15
def crc_initial(c):
crc = 0
c = c << 8
for j in range(8):
if (crc ^ c) & 0x8000:
crc = (crc << 1) ^ CRCPOLY
else:
crc = crc << 1
c = c << 1
crc = crc & 0xFFFF
return crc
crc_table = [ crc_initial(i) for i in range(256) ]
def get_crc(data):
crc = 0
for d in data + [0xff, 0xff]:
if d < 0 or d > 255:
raise ValueError("data value out of bounds")
crc_h = crc >> 8
crc = ((crc << 8) | d) & 0xFFFF
crc = crc ^ crc_table[crc_h]
return [crc >> 8, crc & 0xff]
def check_crc(data):
return get_crc(data[:-2]) == data[-2:]
class LLCP:
def __init__(self, port):
self.packet_id = 0
self.serial = serial.Serial(port, 19200, timeout=0.5)
def _tx_data(self, data):
print("TX %r" % data)
self.serial.write(data)
self.receive_packet()
def receive_packet(self):
packet = []
header = self.serial.read()
if not header:
print("RX timeout")
return []
header = ord(header)
packet.append(header)
if header == SOH_header or \
header == STX_header or \
header == ETB_header or \
header == ETX_header or \
header == ACK_header or \
header == NAK_header:
packet_id = self.serial.read()
if not packet_id:
print("packet_id timeout")
return []
packet_id = ord(packet_id)
packet.append(packet_id)
if header != ACK_header and header != NAK_header:
length = self.serial.read()
if not length:
print("length timeout")
return []
length = ord(length)
if length > MAXDATLEN:
print("length invalid")
return []
packet.append(length)
data = self.serial.read(length)
if len(data) < length:
print("data length too short")
return []
packet.extend(data)
crch, crcl = self.serial.read(2)
if not crch or not crcl:
print("crc timeout")
return []
packet.append(crch)
packet.append(crcl)
if header == SOH_header:
print("SOH")
if header == STX_header:
print("STX")
if header == ETB_header:
print("ETB")
if header == ETX_header:
print("ETX")
if header == ACK_header:
print("ACK")
if header == NAK_header:
print("NAK")
if check_crc(packet):
print("RX CRC Valid")
if header != ACK_header and header != NAK_header:
print("Send ACK")
ack_data = [ACK_header, packet_id]
ack_data.extend(get_crc(ack_data))
self._tx_data(ack_data)
else:
print("RX CRC INVALID")
if header != ACK_header and header != NAK_header:
print("Send NAK")
ack_data = [NAK_header, packet_id]
ack_data.extend(get_crc(ack_data))
self._tx_data(ack_data)
print("RX %r" % packet)
return packet
def transmit(self, message):
self.packet_id += 1
data = []
if len(message) < MAXDATLEN:
data.append(STX_header)
data.append(self.packet_id)
data.append(len(message))
data.extend(message)
data.extend(get_crc(data))
self._tx_data(data)
else:
h = SOH_header
sent_bytes = 0
while sent_bytes < len(message):
message_part = message[sent_bytes:sent_bytes+MAXDATLEN]
data.append(h)
data.append(self.packet_id)
data.append(len(message_part))
data.extend(message_part)
data.extend(get_crc(data))
self._tx_data(data)
sent_bytes += len(message_part)
h = ETB_header
if len(message) - sent_bytes < MAXDATLEN:
h = ETX_header
llcp = LLCP("/dev/ttyUSB0")
LnkRegister = 129
GetComponentList = 39
GetCurrentFrequency = 41
# Send a Link Register On message
print("Send a LnkRegister")
for i in range(4):
llcp.transmit([LnkRegister, 1])
rx = llcp.receive_packet()
print()
if rx:
break
print("Send invalid opcode")
llcp.transmit([78])
llcp.receive_packet()
print()
print("Send GetComponentList")
llcp.transmit([GetComponentList])
llcp.receive_packet()
print()
print("Send GetCurrentFrequency")
llcp.transmit([GetCurrentFrequency])
llcp.receive_packet()
print()
print("Send a LnkRegister Off")
llcp.transmit([LnkRegister, 0])
llcp.receive_packet()
print()
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