Revision as of 17:11, 29 December 2020

Introduction

TireX is a powerful and versatile multi-zone tire temperature sensor designed for motorsports applications.

Features

High Performance

TireX can be configured to report up to 16 temperature zones, supporting sample rates up to 64Hz via CAN bus with the powerful embedded 32 bit processor.

Rugged and Compact

TireX features a rugged, low profile design with a wide field of view for space constrained environments.

Flexible Setup

Temperature zones and sensor calibration is customizable by the end user
Sensor position can be assigned to provide consistent data reporting between left and right sides of vehicle.
CAN bus can be set for 1MB or 500K (default is 1MB)

Specifications

Specifications are preliminary and subject to change

Feature	Description
Sensor type	Thermal array
Sensor Resolution	16 x 12 (196 pixels)
Object temperature range	0 - 127.5C (tire temperature mode) / 0 - 255C (full frame mode)
Field of view	110 x 75 degrees
Accuracy	1C
Temperature zones (tire)	1 / 2 / 4 / 8 / 16
Sample rate	0.5 - 64Hz (Tire temperature mode) 0.5 - 10Hz (Full frame mode)
Processing Engine	32 bit
Configurable positions	4 (Left-Front, Right-Front, Left-Rear, Right-Rear); Reversible orientation
Emissivity	Configurable (0.95 default)
Ambient temperature compensation	Automatic (adjustable offset)
Electrical
Interface	CAN 2.0
Supply voltage	6 - 12v
Power	200mW
Harness	M8 4P Male, 250mm length
CAN bus
CAN baud rate	500K and 1M, jumper configurable (1M default)
Address space	4 separate address spaces (configurable via jumper)
Termination	No Termination (configurable via jumper)
Physical / Environmental
Construction	CNC aluminum
Dimensions	64 x 46 x 12.5mm
Weight	10 grams
Operating temperature	-40 - 85C
IP rating	IP65

Dimensions / Mounting

Mounting Distance

TireX has a wide aspect ratio of 110 degrees, so you can use some trigonometry to calculate the distance. Here are some examples:

205 width = 71mm
225 width = 79mm
235 width = 82mm
245 width = 85mm
255 width = 89mm
275 width = 96mm
315 width = 110mm

Here's a convenient online calculator

Tip: you can mount TireX at a further distance if you use the middle channels. Example:

if only using 8 channel, you can mount 2x the distance
If only using 4 channels, you can mout 4x the distance

Note: 4 channels is often the resolution of choice to reduce the bulk of data generated, and gives perfectly adequate results for determining tire performance.

Electrical / CAN connection

Connection is provided by a standard industrial M8 4P male plug. Pigtails and connectors are available from Autosport Labs, or 3rd parties.

Pin	Connecton
Pin 1	CAN Low
Pin 2	Voltage supply (6-14v)
Pin 3	CAN High
Pin 4	Ground

Zone Configuration

Up to 16 configurable temperature zones

TireX can be configured to report up to 16 temperature zones across the sensor's entire field of vision.

When configured for 2 or more zones, temperature for zones are reported in the order of inside through outside edge.

Zones	Coverage
1	Averaged across the entire field of vision
2	Each zone averaged across 1/2 the field of vision
4	Each zone averaged across 1/4 the field of vision
8	Each zone averaged across 1/8 the field of vision

Reversible orientation based on sensor position

TireX zones are reversed based on the configured sensor position (left vs right side) to allow identical physical sensor mounting orientation between sides.

CAN bus protocol

Overview

The CAN bus API provides the configuration, control and sensor broadcast interface for TireX

Conventions

Formula

Conversion formulas are expressed as converting the CAN encoded value to real-world value.

Example:
- Encoded value in CAN message: 95
- Formula: A / 100
- Real-world value: 0.95

Data encoding

Endian

16 and 32 bit values are encoded as little endian.

Single and mulit-byte values

Value	Symbol Reference
8 Bit values	A
16 bit values	A (low byte) / B (high byte)
32 Bit values	A (low byte) / B / C / D (high byte)

CAN Baud rate

1M and 500K rates are supported.

1M is enabled by default; cut the jumper labeled BAUD on the bottom of TireX to enable 500K rate.

CAN base ID

A configured TireX sensor will have a CAN base address that is a combination of the Main Base ID + Position Offset based on the installed position of the sensor on the vehicle. This combination creates a final Sensor Base ID.

All broadcast and configuration CAN messages is offset from the final calculated Sensor Base ID.

Default Main Base ID

Default Main CAN base ID is 0xA100 (41216)

Adjusting Main Base ID

The base address is determined by the state of the ADR1 and ADR2 jumpers. By default, the jumpers are closed (bridged); the jumper can be opened by cutting the trace between the pads. To re-close the jumper, add a small amount of solder to bridge the gap between the pads you want to close.

Note: In the vast majority of the cases you can use the default Main Base ID of 0xA100.

ADR2 Jumper	ADR1 Jumper	Address
Closed	Closed	0xA100 (41216)
Closed	Open	0xB100 (45312)
Open	Closed	0xC100 (49408)
Open	Open	0xD100 (53504)

Opening the jumper ADR1 will add (0x1000) 4096 to the base ID
Opening the jumper ADR2 will add (0x2000) 8192 to the base ID
Opening both jumpers ADR1 and ADR2 will add (0x3000) 12288 to the base ID.

Sensor Position Offset

The sensor position will offset the Main Base ID by the position of the sensor as defined in the table, to set the final Sensor Base ID.

Position ID	Sensor Position	Offset
0	Left-Front	0x0 (0)
1	Right-Front	0x100 (256)
2	Left-Rear	0x200 (512)
3	Right-Rear	0x300 (768)

Example: default base address (0xA100)

Sensor Position	Final Sensor Base ID
Left-Front	0xA100
Right-Front	0xA200
Left-Rear	0xA300
Right-Rear	0xA400

Note: Single sensor kits are configured as left-front tire position. This can be changed by sending the appropriate configuration message.

CAN Messages

The announcement message is broadcast by TireX once per second for 10 seconds upon power up.

Announcement

CAN ID: Sensor Base ID + 0

Offset	What	Data Type	Formula	Value
0	Sample Rate	unsigned	A * 1	0.5 - 64Hz (0 = 0.5Hz)
1	Temperature Zones	unsigned	A * 1	Number of configured temperature zones (1 / 2 / 4 / 8 / 16)
2	Sensor Position	Unsigned	A * 1	Configured sensor position (0=Left-Front / 1=Right-Front / 2=Left-Rear / 3=Right-Rear)
3	Reserved
4	Reserved
5	Major Version	unsigned	A * 1	Firmware Major Version Number
6	Minor Version	unsigned	A * 1	Firmware Minor Version Number
7	Patch Version	unsigned	A * 1	Firmware Patch version number

Statistics

Broadcast by TireX every 10 seconds.

CAN ID: Sensor Base ID + 2

Offset	What	Data Type	Formula	Value
0	Sensor Ambient Temperature	unsigned	A * 1	0 - 255C
1	Reserved
2	Reserved
3	Reserved
4	Reserved
5	Major Version	unsigned	A * 1	Firmware Major Version Number
6	Minor Version	unsigned	A * 1	Firmware Minor Version Number
7	Patch Version	unsigned	A * 1	Firmware Patch version number

Configuration Preferences

This message is broadcasted to TireX to configure the sensor's preferences. The settings are persisted in TireX's flash memory.

CAN ID: Sensor Base ID + 3

Note: To read the current settings, broadcast a message with this CAN ID with no data (data length of 0) - TireX will reply with the current configuration.

Offset	What	Data Type	Formula	Value
0	Sample Rate	unsigned	A * 1	Rate to report sensor values ( 0.5 - 64Hz) Valid sample rates: 0 (0.5Hz) / 1 (1Hz) / 2 (2Hz) / 4 (4Hz) / 8 (8Hz) / 16 (16Hz) / 32 (32Hz) / 64 (64Hz). Specifying an invalid value will select the default value of 16
1	Temperature zones	unsigned	A * 1	Number of temperature zones. Valid zones: 1 / 2 / 4 / 8 / 16. Specifying an invalid value will select the default value of 4.
2	Sensor Position	unsigned	A * 1	Location of the sensor on the vehicle. This position adjusts the Sensor Base ID. Valid Positions 0 (Left-Front) / 1 (Right-Front) / 2 (Left-Rear) / 3 (Right-Rear). Specifying an invalid value will select the default value of 0 (Left-Front). Note: The sensor position affects the orientation of the sensor zones. Sensor Position 1 and 3 will report temperature zones left - right; Position 0 and 2 will report temperature zones right - left.
3	Frame mode	unsigned	A * 1	0 = Standard (Tire Temperature) mode; 1 = Full Frame mode
4	Reserved
5	Reserved
6	Reserved
7	Reserved

Calibration Preferences

This message is broadcasted to TireX to configure the sensor's calibration. The settings are persisted in TireX's flash memory.

TireX is calibrated at the factory and normally these values will not need to be changed.

CAN ID: Sensor Base ID + 4

Note: To read the current settings, broadcast a message with this CAN ID with no data (data length of 0) - TireX will reply with the current configuration.

Offset	What	Data Type	Formula	Value
0	Emissivity	unsigned	A / 100	Emissivity of the target. Default is 0.95
1	Ambient temperature compensation	unsigned	A * 1	Value in C
2	Sensor Resolution	unsigned	16-19	Sensor ADC resolution, in bits
3	Reserved
4	Reserved
5	Reserved
6	Reserved
7	Reserved

Sensor Temperature Value Broadcast

The following messages will contain the temperature values based on the number of temperature zones configured, broadcast at the currently configured sample rate.

Note: The sensor position affects the orientation of the sensor zones:
- Position 1 and 3 will report temperature zones left - right;
- Position 0 and 2 will report temperature zones right - left.