Vision System Serial Protocol

Message, general format

UART messages sent from the Xavier Jetson, our vision platform, to the RoboMaster Type A Board (MCB) will be a string of bytes in the following format:

Starting offset (bytes)	Length (bytes)	Name	Description
0	1	Header	constant 0xA5
1	1	Data Length [0]	length of data to be read in bytes, n. 8 LSB
2	1	Data Length [1]	length of data to be read in bytes, n. 8 MSB
3	2	Sequence Number	byte is incremented each time a message is sent
5	1	Message Type [0]	a user-chosen "type" flag. 8 LSB
6	1	Message Type [1]	a user-chosen "type" flag. 8 MSB
7	n	Data	The actual data sent

Note that optional CRC bytes have been omitted as they are currently note used while communicating with the vision system. They are used only with referee system communication.

For RX, a general message is parsed into a SerialMessage struct upon arrival. For TX, a SerialMessage is constructed and then transmitted. The generic struct is as follows:

struct SerialMessage
{
    uint8_t headByte;                  ///< Use SERIAL_HEAD_BYTE.
    uint16_t length;                   ///< Must be less than SERIAL_RX_BUFF_SIZE.
    uint16_t type;                     ///< The type is specified and interpreted upon arrival.
    uint8_t data[SERIAL_RX_BUFF_SIZE];
    modm::Timestamp messageTimestamp;  ///< The timestamp is in milliseconds.
    uint8_t sequenceNumber;            ///< Increment this for debugging purposes.
};

Below are the specifications for the different type of messages:

---

Turret bearing

This message is sent from the Jetson to the MCB.

Idx	Attribute	Value
1	Data Length [0]	0x05
2	Data Length [1]	0x00
5	Message type [0]	0x01
6	Message type [1]	0x00
7	pitch[0]	MSB of pitch to 1 decimal place * 10
8	pitch[1]	LSB of pitch to 1 decimal place * 10
9	yaw[0]	MSB of yaw to 1 decimal place * 10
10	yaw[0]	LSB of yaw to 1 decimal place * 10
11	has_target	1 if target acquired, 0 otherwise

To send turret bearings to the MCB, take the targeted pitch and yaw angles (in degrees), multiply by 10, then truncate to integers.

Example Message:

Data to be sent: pitch=12.6, yaw=68.0

Multiply pitch by 10 and you get 126, multiply yaw by 10 and you get 690.

Hex Representation of 126 is 0x007E, 680 is 0x02AB

Final Message:

0x69 0x01 0x00 0x04 0x00 0x7E 0x02 0xB2

Turret feedback

This message is sent from the MCB to the Jetson. It, along with the other messages below are interleaved and sent round robin style.

Idx	Attribute	Value
1	Data Length [0]	0x04
2	Data Length [1]	0x00
5	Message type [0]	0x01
6	Message type [1]	0x00
7	pitch[0]	MSB of pitch to 1 decimal place * 10
8	pitch[1]	LSB of pitch to 1 decimal place * 10
9	yaw[0]	MSB of yaw to 1 decimal place * 10
10	yaw[0]	LSB of yaw to 1 decimal place * 10

Turret bearings feedback from the MCB are pitch and yaw angles (in degrees) are multiplied by 10, then truncate to integers.

Telemetry data

This message is sent from the MCB to the Jetson. The telemetry data includes IMU angles, gyro, and accel data, as well as chassis wheel velocity.

Idx	Attribute	Value
1	Data Length [0]	0x1A
2	Data Length [1]	0x00
5	Message type [0]	0x02
6	Message type [1]	0x00
7	x_accel[0]	LSB of x accel to 2 decimal place * 100
8	x_accel[1]	MSB of x accel to 2 decimal place * 100
9	y_accel[0]	LSB of y accel to 2 decimal place * 100
10	y_accel[1]	MSB of y accel to 2 decimal place * 100
11	z_accel[0]	LSB of z accel to 2 decimal place * 100
12	z_accel[1]	MSB of z accel to 2 decimal place * 100
13	imu_roll[0]	LSB of IMU roll calculation to 2 decimal place * 100
14	imu_roll[1]	MSB of IMU roll calculation to 2 decimal place * 100
15	imu_pitch[0]	LSB of IMU pitch calculation to 2 decimal place * 100
16	imu_pitch[1]	MSB of IMU pitch calculation to 2 decimal place * 100
17	imu_yaw[0]	LSB of IMU yaw calculation to 2 decimal place * 100
18	imu_yaw[1]	MSB of IMU yaw calculation to 2 decimal place * 100
19	x_gyro[0]	LSB of x gyro to 2 decimal place * 100
20	x_gyro[1]	MSB of x gyro to 2 decimal place * 100
21	y_gyro[0]	LSB of y gyro to 2 decimal place * 100
22	y_gyro[1]	MSB of y gyro to 2 decimal place * 100
23	z_gyro[0]	LSB of z gyro to 2 decimal place * 100
24	z_gyro[1]	MSB of z gyro to 2 decimal place * 100
25	rightFrontWheelRPM[0],	LSB of the right front wheel's RPM
26	rightFrontWheelRPM[1]	MSB of the right front wheel's RPM
27	leftFrontWheelRPM[0],	LSB of the left front wheel's RPM
28	leftFrontWheelRPM[1]	MSB of the left front wheel's RPM
29	leftBackWheeRPM[0],	LSB of the left back wheel's RPM
30	leftBackWheeRPM[1]	MSB of the left back wheel's RPM
31	rightBackWheelRPM[0]	LSB of the right back wheel's RPM
32	rightBackWheelRPM[1]	MSB of the right back wheel's RPM

Accel data in meters per second squared and gyro data in degrees per second are multiplied by 100, then truncated to a 16 bit integer.

Robot type ID

This message is sent from the MCB to the Jetson.

Idx	Attribute	Value
1	Data Length [0]	0x01
2	Data Length [1]	0x00
5	Message type [0]	0x04
6	Message type [1]	0x00
7	robot_type[0]	Raw robot type, per referee system specification

Auto aim request

This message is sent from the MCB to the Jetson.

This message is used to either request an aim request or cease requesting auto aim requests (see first message). This is the only message not sent every round robin iteration. It is only sent if an aim request has been queued.

Idx	Attribute	Value
1	Data Length [0]	0x01
2	Data Length [1]	0x00
5	Message type [0]	0x05
6	Message type [1]	0x00
7	request_cv[0]	0 for cease request, 1 for new auto aim request