CAN Bus protocol

CAN message structure is defined by two main parts: cmd and data.

  1. cmd (8 bits - 1 byte): First byte refers to the Message Type.

    Messages Type are defined as follows:

    Type

    Value

    Description

    t_arbitration

    0

    Arbitration message

    t_version

    1

    Version request / response

    t_pwm_0_3_set

    2

    PWMs 0 to 3

    t_pwm_4_7_set

    3

    PWMs 4 to 7

    4

    Reserved

    t_esc_tm

    5

    Scorpion Tribunus ESC telemetry data

    t_esc_tm2

    6

    Jeti ESC telemetry data

    t_bec_tm1

    7

    Jeti BEC telemetry data 1

    t_bec_tm2

    8

    Jeti BEC telemetry data 2

    t_temp_tm

    9

    Jeti Temperature sensor telemetry data

    t_mcu_cmd

    10

    Lift MCU battery command

    t_pwm_8_11_set

    11

    PWMs 8 to 11

    t_pwm_12_15_set

    12

    PWMs 12 to 15

    t_pwm_16_19_set

    13

    PWMs 16 to 19

    14

    Reserved

    15

    Reserved

    t_cmd_maint

    16

    Command to go to Maintenance Mode

    t_stick_sel

    17

    Command for Stick selection

    t_mcu_tm1

    18

    Lift MCU telemetry data 1

    t_mcu_tm2

    19

    Lift MCU telemetry data 2

Note

All these Message Type are defined as a “Matcher” in the CAN custom messages configuration. For example, for PWMs 0-3, the Message Type will be configured as follows:

../_images/message_type_example.png

Message Type example

  • Value: 2. This is because it is the value for the message for PWMs 0 to 3 (it is indifferent to the PWM number).

  • Bits: 8. This is because the Message Type is an 8-bit message.

  1. data (up to 56 bits - 8 bytes): The following bytes refer to the Message data.

The following examples include complete messages, so each beginning corresponds to Message Type.

Arbitration messages

Status Message

Status message summarizes the status of all autopilots. This message is a producer in the 4x PDI Builder configuration, since it is created from the CAN messages of all three or four autopilots.

Byte

Position

Value

Description

0

0 - 7

0x00

Header

1

0 - 7

0xFF

Status message Header

2

0 - 6

0 - 3

Selected AP (0 = AP1, 1 = AP2, 2 = AP3, 3 = External AP)

7

0 - 1

Arbitration OFF/ON

3

0

0 - 1

AP1 Alive

1

0 - 1

AP2 Alive

2

0 - 1

AP3 Alive

3

0 - 1

External AP Alive

4

0 - 1

AP1 Ready

5

0 - 1

AP2 Ready

6

0 - 1

AP3 Ready

7

0 - 1

External AP Ready

4

0

0 - 1

CBIT. System error. Will fail if any of the below items fail.

1

0 - 1

PBIT. System Boot Ok.

2

0 - 1

PDI Ok. Will fail if there is an error in configuration files.

3

0 - 1

Memory Allocation OK

4

0 - 1

CAN A Ok

5

0 - 1

CAN B Ok

6

0 - 1

CIO Low Task Ok

7

0 - 1

CIO High Task Ok

5

0

0 - 1

Power OK. All power indicators are OK.

1

0 - 1

A Bus Voltage Ok

2

0 - 1

B Bus Voltage Ok

3

0 - 1

Arbiter Voltage Ok

4

0 - 1

AP1 Voltage Ok

5

0 - 1

AP2 Voltage Ok

6

0 - 1

AP3 Voltage Ok

7

0 - 1

Arbiter Mode. 1 = Normal, 0 = Maintenance

Score Message

Score message contains the final score of an specific autopilot. This message is a producer in the 4x PDI Builder configuration, so it is created from the CAN messages of all three or four autopilots.

Byte

Position

Value

Description

0

0 - 7

0x00

Header

1

0 - 7

0 - 3

Autopilot ID (0 = AP1, 1 = AP2, 2 = AP3, 3 = External AP)

2 - 5

0 - 31

0 - 0xFFFF FFFF

Autopilot Arbitration Score

Ready Message

Ready message is sent from Autopilot 1x to Arbiter. It tells whether an Autopilot 1x is ready to fly or not. It is as consumer in the 4x PDI Builder configuration, so it is stored in memory.

Byte

Position

Value

Description

0

0 - 7

0x00

Header

1

0 - 7

0xFF

Ready Message Header

2

0 (1 bit)

0 - 1

Ready/Not Ready

Arbitration Message

Arbitration message tells the arbitration value of a specific variable. It is as consumer in the 4x PDI Builder configuration, since it is stored in memory.

Byte

Position

Value

Description

0

0 - 7

0x00

Header

1

0 - 7

0 - 31

Arbitration Variable Number

2 - 5

0 - 31

0 - 0xFFFF FFFF

Arbitration Variable Value