TODO

• Optimize measurements so all the data is stored ONLY in system variable.
• Add second IMU
• Add filtering to IMU data
• Add depth sensing
• Test control loops
• Add packet for telemetry setup
• Allow multiple telemetry links
• Add tasks stats to system variables
• Reorganize control loop so info about used PID controlers, variables etc can be stored in configuration file
• Implementation of EKF

Comunication protocol

Each message sended from and to TCM must follow protocol described in this section. The bit order is LSB first.

Packet structure

Byte name	value/length
Header 0	0x69
Header 1	0x68
Payload length	byte
Message type	byte
Payload	0 - 500
Checksum MSB	byte
Checksum LSB	byte

Checksum calculation

Cheksum is 16-bit CRC-CCITT. It is calculated with following function:

uint16_t calculateChecksum(uint8_t* data_p, uint16_t length)
{
    uint8_t x;
    uint16_t crc = 0xFFFF;

    while (length--){
        x = crc >> 8 ^ *data_p++;
        x ^= x>>4;
        crc = (crc << 8) ^ ((uint16_t)(x << 12)) ^ ((uint16_t)(x <<5)) ^ ((uint16_t)x);
    }
    return crc;
}

Message types

They are few types of message that you can send or receive with TCM. If the payload is not described it means that it length is 0.

Message types to TCM

Type	value
Request	0x0
Service	0x1
Control	0x2

Request message

User can request data from TCM.

Type	value	Service mode required
PID	0x0	No
Control matrix	0x1	Yes
Data	0x2	No

Service message

These messages are used to test, set, load and save new settings.

Type	value	Service mode required
Enter service mode	0x0	No
Reboot	0x1	Yes
Enable direct thrusters ctrl	0x2	Yes
Disable direct thrusters ctrl	0x3	Yes
Direct motors ctrl	0x4	Yes
Direct motors ctrl via matrix	0x5	Yes
Save settings	0x6	Yes
Load settings from flash	0x7	Yes
New PID values	0x8	No

Control message

The only option to control the boat is using sticks. Stick values are float big endian. It is possible but not mandatory to send up to 16 stick commands in one message.

For now sticks are corresponding to the control inputs as follow:

- stick 0 - roll
- stick 1 - pitch
- stick 2 - yaw
- stick 3 - vertical
- stick 4 - forward
- stick 5 - enable thrusters

Example message for commanding the sticks:

Byte name	value/length
Header 0	0x69
Header 1	0x68
Payload length (20) MSB	byte
Payload length (20) LSB	byte
0x2 - ctrl msg	byte
stick 0	4 bytes (float)
stick 1	4 bytes (float)
stick 2	4 bytes (float)
stick 3	4 bytes (float)
stick 4	4 bytes (float)

|Checksum MSB|byte| |Checksum LSB|byte|

Message types from TCM

Type	value
PID	0x3
Control matrix	0x4
Heart beat	0x5
Service confirm	0x6
Telemetry	0x7
Variable	0x8

PID

Heart beat

TCM is sending heart beat packet twice a second.

Service confirm

After each service message received TCM is responding with this packet.

Telemetry

Compiling

• Copy following lines to install vcpkg:

  • linux: '. <(curl https://aka.ms/vcpkg-init.sh -L)'
  • windows: 'iex (iwr -useb https://aka.ms/vcpkg-init.ps1)'

• Clone TMC code from github

• Open TMC folder with VSCode

• Install Embeded Tools extension

• Install CMake Tools extension

• in terminal type vcpkg activate

Thats it.