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:

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.

2. 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