Added serial communication script

(authored by Carson)

rb_ws/src/buggy/scripts/serial/host_comm.py

@@ -0,0 +1,189 @@
+import struct
+from serial import Serial
+from dataclasses import dataclass
+
+class Crc16:
+    def __init__(self):
+        self.accum = 0
+
+    def update(self, b):
+        if isinstance(b, int):
+            assert(0 <= b < 256)
+
+            crc_table = [
+                0x0000, 0x8005, 0x800F, 0x000A, 0x801B, 0x001E, 0x0014, 0x8011,
+                0x8033, 0x0036, 0x003C, 0x8039, 0x0028, 0x802D, 0x8027, 0x0022,
+                0x8063, 0x0066, 0x006C, 0x8069, 0x0078, 0x807D, 0x8077, 0x0072,
+                0x0050, 0x8055, 0x805F, 0x005A, 0x804B, 0x004E, 0x0044, 0x8041,
+                0x80C3, 0x00C6, 0x00CC, 0x80C9, 0x00D8, 0x80DD, 0x80D7, 0x00D2,
+                0x00F0, 0x80F5, 0x80FF, 0x00FA, 0x80EB, 0x00EE, 0x00E4, 0x80E1,
+                0x00A0, 0x80A5, 0x80AF, 0x00AA, 0x80BB, 0x00BE, 0x00B4, 0x80B1,
+                0x8093, 0x0096, 0x009C, 0x8099, 0x0088, 0x808D, 0x8087, 0x0082,
+                0x8183, 0x0186, 0x018C, 0x8189, 0x0198, 0x819D, 0x8197, 0x0192,
+                0x01B0, 0x81B5, 0x81BF, 0x01BA, 0x81AB, 0x01AE, 0x01A4, 0x81A1,
+                0x01E0, 0x81E5, 0x81EF, 0x01EA, 0x81FB, 0x01FE, 0x01F4, 0x81F1,
+                0x81D3, 0x01D6, 0x01DC, 0x81D9, 0x01C8, 0x81CD, 0x81C7, 0x01C2,
+                0x0140, 0x8145, 0x814F, 0x014A, 0x815B, 0x015E, 0x0154, 0x8151,
+                0x8173, 0x0176, 0x017C, 0x8179, 0x0168, 0x816D, 0x8167, 0x0162,
+                0x8123, 0x0126, 0x012C, 0x8129, 0x0138, 0x813D, 0x8137, 0x0132,
+                0x0110, 0x8115, 0x811F, 0x011A, 0x810B, 0x010E, 0x0104, 0x8101,
+                0x8303, 0x0306, 0x030C, 0x8309, 0x0318, 0x831D, 0x8317, 0x0312,
+                0x0330, 0x8335, 0x833F, 0x033A, 0x832B, 0x032E, 0x0324, 0x8321,
+                0x0360, 0x8365, 0x836F, 0x036A, 0x837B, 0x037E, 0x0374, 0x8371,
+                0x8353, 0x0356, 0x035C, 0x8359, 0x0348, 0x834D, 0x8347, 0x0342,
+                0x03C0, 0x83C5, 0x83CF, 0x03CA, 0x83DB, 0x03DE, 0x03D4, 0x83D1,
+                0x83F3, 0x03F6, 0x03FC, 0x83F9, 0x03E8, 0x83ED, 0x83E7, 0x03E2,
+                0x83A3, 0x03A6, 0x03AC, 0x83A9, 0x03B8, 0x83BD, 0x83B7, 0x03B2,
+                0x0390, 0x8395, 0x839F, 0x039A, 0x838B, 0x038E, 0x0384, 0x8381,
+                0x0280, 0x8285, 0x828F, 0x028A, 0x829B, 0x029E, 0x0294, 0x8291,
+                0x82B3, 0x02B6, 0x02BC, 0x82B9, 0x02A8, 0x82AD, 0x82A7, 0x02A2,
+                0x82E3, 0x02E6, 0x02EC, 0x82E9, 0x02F8, 0x82FD, 0x82F7, 0x02F2,
+                0x02D0, 0x82D5, 0x82DF, 0x02DA, 0x82CB, 0x02CE, 0x02C4, 0x82C1,
+                0x8243, 0x0246, 0x024C, 0x8249, 0x0258, 0x825D, 0x8257, 0x0252,
+                0x0270, 0x8275, 0x827F, 0x027A, 0x826B, 0x026E, 0x0264, 0x8261,
+                0x0220, 0x8225, 0x822F, 0x022A, 0x823B, 0x023E, 0x0234, 0x8231,
+                0x8213, 0x0216, 0x021C, 0x8219, 0x0208, 0x820D, 0x8207, 0x0202
+            ]
+
+            i = ((self.accum >> 8) ^ b) & 0xFF;
+            i %= 256
+            self.accum = ((self.accum << 8) & 0xFF00) ^ crc_table[i];
+        else:
+            for one_byte in b:
+                self.update(one_byte)
+
+SYNC_WORD = b'\xAA\xFF\x00\x55'
+
+MAX_PAYLOAD_LEN = 100
+
+MSG_TYPE_DEBUG    = b'DB'
+MSG_TYPE_ODOMETRY = b'OD'
+MSG_TYPE_STEERING = b'ST'
+MSG_TYPE_BRAKE    = b'BR'
+
+@dataclass
+class Odometry:
+    x: float
+    y: float
+
+class IncompletePacket(Exception):
+    pass
+
+class ChecksumMismatch(Exception):
+    pass
+
+class Comms:
+    def __init__(self, path_to_port):
+        self.port = Serial(path_to_port, 1_000_000)
+        self.rx_buffer = b''
+
+    def send_packet_raw(self, msg_type: bytes, payload: bytes):
+        assert(len(msg_type) == 2)
+        assert(len(payload) < MAX_PAYLOAD_LEN)
+
+        checksum = Crc16()
+        def write_and_checksum(data: bytes):
+            nonlocal checksum
+
+            self.port.write(data)
+            checksum.update(data)
+
+        self.port.write(SYNC_WORD)
+        write_and_checksum(msg_type)
+        write_and_checksum(len(payload).to_bytes(2, 'little'))
+        write_and_checksum(payload)
+        self.port.write(checksum.accum.to_bytes(2, 'little'))
+
+    def send_steering(self, angle: float):
+        self.send_packet_raw(MSG_TYPE_STEERING, struct.pack('<d', angle))
+
+    def read_packet_raw(self):
+        self.rx_buffer += self.port.read_all() #type:ignore
+
+        try:
+            return self._try_parse_buffer()
+        except IncompletePacket:
+            return None
+        except ChecksumMismatch:
+            return None
+
+
+    def _try_parse_buffer(self):
+        while True:
+            checksum = Crc16()
+            index = 0
+            def read(count: int):
+                nonlocal index
+
+                if index + count > len(self.rx_buffer):
+                    raise IncompletePacket()
+
+                data = self.rx_buffer[index:][:count]
+                index += count
+                return data
+
+            def read_and_checksum(count: int):
+                nonlocal checksum
+
+                data = read(count)
+                checksum.update(data)
+                return data
+
+            if read(1) != SYNC_WORD[0:1]:
+                self.rx_buffer = self.rx_buffer[1:]
+                continue
+            if read(1) != SYNC_WORD[1:2]:
+                self.rx_buffer = self.rx_buffer[1:]
+                continue
+            if read(1) != SYNC_WORD[2:3]:
+                self.rx_buffer = self.rx_buffer[1:]
+                continue
+            if read(1) != SYNC_WORD[3:4]:
+                self.rx_buffer = self.rx_buffer[1:]
+                continue
+
+            msg_type = read_and_checksum(2)
+            msg_len = int.from_bytes(read_and_checksum(2), 'little')
+
+            if msg_len > MAX_PAYLOAD_LEN:
+                self.rx_buffer = self.rx_buffer[1:]
+                continue
+
+            payload = read_and_checksum(msg_len)
+
+            rx_crc = int.from_bytes(read(2), 'little')
+
+            self.rx_buffer = self.rx_buffer[4 + 3 + 2 + msg_len + 2:]
+
+            if rx_crc != checksum.accum:
+                raise ChecksumMismatch()
+
+            return (msg_type, payload)
+
+    def read_packet(self):
+        packet = self.read_packet_raw()
+        if packet is None:
+            return None
+
+        msg_type, payload = packet
+        if msg_type == MSG_TYPE_ODOMETRY:
+            # Odometry message
+            x, y = struct.unpack('<dd', payload)
+            return Odometry(x, y)
+        else:
+            print(f'Unknown packet type {msg_type}')
+
+
+def main():
+    comms = Comms('/dev/tty.usbserial-1140')
+
+    print('Starting!')
+
+    while True:
+        packet = comms.read_packet()
+        if packet is not None:
+            print(packet)
+            comms.send_steering(1234.5)
+
+if __name__ == '__main__':
+    main()