def convert_to_bytes(msg): """ Re-builds the MAVLink byte stream from mavros_msgs/Mavlink messages. """ payload_octets = len(msg.payload64) msg_len = 6 + msg.len # header + payload length if payload_octets < msg.len / 8: raise ValueError( "Specified payload length is bigger than actual payload64") msgdata = bytearray( struct.pack('<BBBBBB%dQ' % payload_octets, 254, msg.len, msg.seq, msg.sysid, msg.compid, msg.msgid, *msg.payload64)) if payload_octets != msg.len / 8: # message is shorter than payload octets msgdata = msgdata[:msg_len] if hasattr(mag, 'checksum'): # since #286 Mavlink.msg save original checksum, so recalculation not needed. crc16 = msg.checksum else: # from MAVLink.decode() message_type = mavutil.mavlink.mavlink_map[msg.msgid] crc_extra = message_type.crc_extra # calculate crc16 crcbuf = msgdata[1:] crcbuf.append(crc_extra) crc16 = x25crc(crcbuf).crc # finalize msgdata += struct.pack('<H', crc16) return msgdata
def convert_to_bytes(msg): """ Re-builds the MAVLink byte stream from mavros_msgs/Mavlink messages. """ payload_octets = len(msg.payload64) msg_len = 6 + msg.len # header + payload length if payload_octets < msg.len / 8: raise ValueError("Specified payload length is bigger than actual payload64") msgdata = bytearray( struct.pack( '<BBBBBB%dQ' % payload_octets, 254, msg.len, msg.seq, msg.sysid, msg.compid, msg.msgid, *msg.payload64)) if payload_octets != msg.len / 8: # message is shorter than payload octets msgdata = msgdata[:msg_len] # from MAVLink.decode() message_type = mavutil.mavlink.mavlink_map[msg.msgid] crc_extra = message_type.crc_extra # calculate crc16 crcbuf = msgdata[1:] crcbuf.append(crc_extra) crc16 = x25crc(crcbuf).crc # finalize msgdata += struct.pack('<H', crc16) return msgdata
def replace_seq(msg, seq): """ from https://mavlink.io/en/about/overview.html uint8_t magic; ///< protocol magic marker uint8_t len; ///< Length of payload uint8_t incompat_flags; ///< flags that must be understood uint8_t compat_flags; ///< flags that can be ignored if not understood uint8_t seq; ///< Sequence of packet uint8_t sysid; ///< ID of message sender system/aircraft uint8_t compid; ///< ID of the message sender component uint8_t msgid 0:7; ///< first 8 bits of the ID of the message uint8_t msgid 8:15; ///< middle 8 bits of the ID of the message uint8_t msgid 16:23; ///< last 8 bits of the ID of the message uint8_t payload[max 255]; ///< A maximum of 255 payload bytes uint16_t checksum; ///< X.25 CRC :param msg: MAVLink message from PX4 :param seq: New sequence value :return: bytes object for the message buffer """ data = msg.get_msgbuf() data[MAVLINK_SEQ_BYTE] = seq % BYTE_MAX cc = x25crc(bytes(data)[1:-2]) if msg.crc_extra: cc.accumulate(struct.pack('B', msg.crc_extra)) data[-2], data[-1] = cc.crc & BYTE_MAX, cc.crc >> 8 return bytes(data)
def convert_to_bytes(msg): """ This function build wire byte stream from mavros_msgs/Mavlink """ pay_len = len(msg.payload64) last_len = 0 if pay_len < msg.len / 8: raise ValueError("Message length are bigger than payload64") if pay_len != msg.len / 8: # message are shorter than payload quads pay_len = msg.len / 8 last_len = msg.len % 8 msgdata = bytearray( struct.pack( '<BBBBBB%dQ' % pay_len, 254, msg.len, msg.seq, msg.sysid, msg.compid, msg.msgid, *(msg.payload64[:pay_len]))) if last_len: q = struct.unpack('8B', struct.pack('<Q', msg.payload64[pay_len])) msgdata += bytearray(q[:last_len]) # from MAVLink.decode() type = mavutil.mavlink.mavlink_map[msg.msgid] crc_extra = type.crc_extra # calculate crc16 crcbuf = msgdata[1:] crcbuf.append(crc_extra) crc16 = x25crc(crcbuf).crc # finalize msgdata += struct.pack('<H', crc16) return msgdata
def convert_to_bytes(msg): """ This function build wire byte stream from mavros_msgs/Mavlink """ pay_len = len(msg.payload64) last_len = 0 if pay_len < msg.len / 8: raise ValueError("Message length are bigger than payload64") if pay_len != msg.len / 8: # message are shorter than payload quads pay_len = msg.len / 8 last_len = msg.len % 8 msgdata = bytearray( struct.pack('<BBBBBB%dQ' % pay_len, 254, msg.len, msg.seq, msg.sysid, msg.compid, msg.msgid, *(msg.payload64[:pay_len]))) if last_len: q = struct.unpack('8B', struct.pack('<Q', msg.payload64[pay_len])) msgdata += bytearray(q[:last_len]) # from MAVLink.decode() type = mavutil.mavlink.mavlink_map[msg.msgid] crc_extra = type.crc_extra # calculate crc16 crcbuf = msgdata[1:] crcbuf.append(crc_extra) crc16 = x25crc(crcbuf).crc # finalize msgdata += struct.pack('<H', crc16) return msgdata
def __init__(self, addr=0, data=[], length=0, retries=3): self.addr = addr self.data = data self.length = length self.checksum = x25crc((bytearray(data))) self.messageCounter = 0 self.ack = 0 self.retries = retries
def __init__(self, addr=0, data=[], length=0, retries = 3): self.addr=addr self.data=data self.length=length self.checksum = x25crc((bytearray(data))) self.messageCounter=0 self.ack=0 self.retries = retries
def _decode(self, msgbuf): ''' Decode a buffer as a MAVLink message ''' try: magic, mlen, seq, srcSystem, srcComponent, msgId = struct.unpack('cBBBBB', msgbuf[:6]) except struct.error as emsg: raise Exception('Unable to unpack MAVLink header: %s' % emsg) if ord(magic) != 254: raise Exception("invalid MAVLink prefix '%s'" % magic) if mlen != len(msgbuf)-8: raise Exception('invalid MAVLink message length. Got %u expected %u, msgId=%u' % (len(msgbuf) - 8, mlen, msgId)) if not msgId in mavlink.mavlink_map: raise Exception('unknown MAVLink message ID %u' % msgId) # decode the payload type = mavlink.mavlink_map[msgId] fmt = type.format order_map = type.orders len_map = type.lengths crc_extra = type.crc_extra # decode the checksum try: crc, = struct.unpack('<H', msgbuf[-2:]) except struct.error as emsg: raise Exception('Unable to unpack MAVLink CRC: %s' % emsg) crcbuf = msgbuf[1:-2] crcbuf = crcbuf + struct.pack('B',crc_extra) crc2 = x25crc(crcbuf) if crc != crc2.crc: raise Exception('invalid MAVLink CRC in msgID %u 0x%04x should be 0x%04x' % (msgId, crc, crc2.crc)) try: t = struct.unpack(fmt, msgbuf[6:-2]) except struct.error as emsg: raise Exception('Unable to unpack MAVLink payload type=%s fmt=%s payloadLength=%u: %s' % ( type, fmt, len(msgbuf[6:-2]), emsg)) tlist = list(t) # handle sorted fields if True: t = tlist[:] if sum(len_map) == len(len_map): # message has no arrays in it for i in range(0, len(tlist)): tlist[i] = t[order_map[i]] else: # message has some arrays tlist = [] for i in range(0, len(order_map)): order = order_map[i] L = len_map[order] tip = sum(len_map[:order]) field = t[tip] if L == 1 or isinstance(field, str): tlist.append(field) else: tlist.append(t[tip:(tip + L)]) # terminate any strings for i in range(0, len(tlist)): if isinstance(tlist[i], str): tlist[i] = str(mavlink.MAVString(tlist[i])) t = tuple(tlist) # construct the message object try: m = type(*t) except Exception as emsg: raise Exception('Unable to instantiate MAVLink message of type %s : %s' % (type, emsg)) m._msgbuf = msgbuf m._payload = msgbuf[6:-2] m._crc = crc m._header = mavlink.MAVLink_header(msgId, mlen, seq, srcSystem, srcComponent) self._value = m return m
def _decode(self, msgbuf): ''' Decode a buffer as a MAVLink message ''' try: magic, mlen, seq, srcSystem, srcComponent, msgId = struct.unpack( 'cBBBBB', msgbuf[:6]) except struct.error as emsg: raise Exception('Unable to unpack MAVLink header: %s' % emsg) if ord(magic) != 254: raise Exception("invalid MAVLink prefix '%s'" % magic) if mlen != len(msgbuf) - 8: raise Exception( 'invalid MAVLink message length. Got %u expected %u, msgId=%u' % (len(msgbuf) - 8, mlen, msgId)) if not msgId in mavlink.mavlink_map: raise Exception('unknown MAVLink message ID %u' % msgId) # decode the payload type = mavlink.mavlink_map[msgId] fmt = type.format order_map = type.orders len_map = type.lengths crc_extra = type.crc_extra # decode the checksum try: crc, = struct.unpack('<H', msgbuf[-2:]) except struct.error as emsg: raise Exception('Unable to unpack MAVLink CRC: %s' % emsg) crcbuf = msgbuf[1:-2] crcbuf = crcbuf + struct.pack('B', crc_extra) crc2 = x25crc(crcbuf) if crc != crc2.crc: raise Exception( 'invalid MAVLink CRC in msgID %u 0x%04x should be 0x%04x' % (msgId, crc, crc2.crc)) try: t = struct.unpack(fmt, msgbuf[6:-2]) except struct.error as emsg: raise Exception( 'Unable to unpack MAVLink payload type=%s fmt=%s payloadLength=%u: %s' % (type, fmt, len(msgbuf[6:-2]), emsg)) tlist = list(t) # handle sorted fields if True: t = tlist[:] if sum(len_map) == len(len_map): # message has no arrays in it for i in range(0, len(tlist)): tlist[i] = t[order_map[i]] else: # message has some arrays tlist = [] for i in range(0, len(order_map)): order = order_map[i] L = len_map[order] tip = sum(len_map[:order]) field = t[tip] if L == 1 or isinstance(field, str): tlist.append(field) else: tlist.append(t[tip:(tip + L)]) # terminate any strings for i in range(0, len(tlist)): if isinstance(tlist[i], str): tlist[i] = str(mavlink.MAVString(tlist[i])) t = tuple(tlist) # construct the message object try: m = type(*t) except Exception as emsg: raise Exception( 'Unable to instantiate MAVLink message of type %s : %s' % (type, emsg)) m._msgbuf = msgbuf m._payload = msgbuf[6:-2] m._crc = crc m._header = mavlink.MAVLink_header(msgId, mlen, seq, srcSystem, srcComponent) self._value = m return m