Difference between revisions of "CAN IDs"

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Line 61:		Line 61:
		+
		+
		+	{| border="1"
		+	|+ '''Table 2: Quality-Bit Mapping'''
		+	! Quality level !! Bit setting
		+	|-
		+	| High || 00
		+	|-
		+	| Medium-high || 01
		+	|-
		+	| Medium-low || 10
		+	|-
		+	| Low || 11
		+	|}
		+
		+
		+	{| border="1"
		+	|+ '''Table 3: Select Jumper Source IDs'''
		+	! ID !! Description
		+	|-
		+	| 0x1 || Original PWM Signals (From Transmitter)
		+	|-
		+	| 0x2 || Generated PWM Signals (From Car)
		+	|}
		+
		+
		+	{| border="1"
		+	|+ '''Table 4: PWM CAN Message format'''
		+	! Quality !! Orientation !! Value
		+	|-
		+	| 31-30 || 29 || 28-0
		+	|}

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Revision as of 10:51, 18 February 2009

This document describes the messages used to transport sensor and actuator information over the ConceptCar CAN Bus. All information regarding the CAN Messages such as IDs, data width, payload and semantics are defined in this document.

CAN IDs and Description

In this section the CAN IDs used by the concept car are defined and a brief description of them is given. Later on the semantics of each message is defined.

Table 1: CAN ID Definition

CAN ID	Identifier	Description
0x08	CANid_WheelSpeedFL	Wheel speed average
0x09	CANid_WheelSpeedFR	Wheel speed average
0x0a	CANid_WheelSpeedRL	Wheel speed average
0x0b	CANid_WheelSpeedRR	Wheel speed average
0x0d	CANid_Voltage	Board supply voltage
0x0e	CANid_ResetCounter	Reset logger counter
0x10	CANid_Inertial_X	Inertial System acceleration X axis
0x11	CANid_Inertial_Y	Inertial System acceleration Y axis
0x12	CANid_Inertial_Yaw	Inertial System yaw rate
0x20	CANid_SelectJumper	Select between original or generated
0x22	CANid_Steering	PWM signal for steering (transmitter signal)
0x25	CANid_Throttle	PWM signal for throttle (transmitter signal)
0x32	CANid_Steering_new	PWM signal for steering (generated)
0x35	CANid_Throttle_new	PWM signal for throttle (generated)
0x400	CANid_ErrorController	Controller error 5 (Table 5)
0x402	CANid_EmergencyKey	Emergency key pressed (Table 6)

Semantics of CAN Messages

In this section the semantics of each CAN Message is described. Some of the messages have special quality descriptors attached to them, which are also described here. The first important definition about the CAN Messages is their size. All of the CAN Messages going over the ConceptCar CAN Bus are 32bit long. While this is not unchangeable, it is necessary to change the code to allow messages bigger than 32bits.

CANid_WheelSpeedXX

Information about wheel speed coming from the wheel speed sensors. The wheel speed is calculated using the time interval between two measures done by the speed sensor. Messages informing the vehicle speed are sent every 20ms. If no measurement is accomplished during the 20ms time slot, no speed information is available. For this reason the semantic of the messages and measurements are defined. A quality descriptor is inserted into the message to describe the quality of the information provided by the message payload, so listeners of this messages can decide what to do with the information. The speed is calculated using the average of measures obtained within the 20ms time slot. When several readings occur during the time slot, the value 2 is said to have a high quality. If the time between measures take longer than 20ms, the quality of the information is decayed and follows equation 1.

Table 2: Quality-Bit Mapping

Quality level	Bit setting
High	00
Medium-high	01
Medium-low	10
Low	11

Table 3: Select Jumper Source IDs

ID	Description
0x1	Original PWM Signals (From Transmitter)
0x2	Generated PWM Signals (From Car)

Table 4: PWM CAN Message format

Quality	Orientation	Value
31-30	29	28-0

CAN Controller Error Messages

Table 5: Controller Error Messages

ID	Identifier	Description
0x1	ErrorType_PulseOutOfBounds	Indicates too short or too long PWM pulses
0x2	ErrorType_PWMFrequency	Indicates a wrong PWM frequency
0x4	ErrorType_NoSignal	Indicates lack of signal (low is longer than 18ms)
0x8	ErrorType_ActorEnteredError	-

CAN Emergency Key Messages

Table 6: Emergency Key Mapping

Button	Bits
1	0x01(001)
2	0x02(010)
3	0x04(100)