RF-17 Sensor Hub Modules

Summary

The RF-17 Sensor Modules were the first custom data acquisition modules to be developed on the Ryerson Formula Racing team. The driving force behind the creation of the modules was: to expand the total IO capabilities of the car (restricted by the ECU), reduce wiring harness complexity and mass, and simplify the addition of various automotive sensors.

Expand

The ECU used by RFR is the Megasquirt 3 Pro, which is a reasonably priced and reasonably capable ECU which allows for an easy EFI implementation for the team. However, the ECU is seriously lacking in analog inputs. Most of the inputs are taken up by critical sensors (such as fuel and oil pressure), leaving virtually none for the vast sensor configurations that are useful for R&D. The ECU does have a CAN interface though, which supports many more sensors to be used and logged by the ECU. Therefore, having CAN-connected modules that can interface with the sensors remotely greatly increases the DAQ capabilities of the vehicle.

Reduce

Assuming the ECU could support all of the needed sensors directly, each sensor requires a direct electrical connection to the ECU and/or the power distribution module. Increasing the sensor count therefore has the overhead of more and more wire running all the way back to the ECU. The harness was also split into a front and rear harness at the firewall for modularity and strain-relief purposes, so adding more sensors to the front section would required a high contact-count connector for the harness interface.

CAN bus, on the other hand, requires two wires (a differential pair) for signaling, as well as two wires for power. It is much easier and more cost effective to run these four wires to 4-5 modules than to run 2-4 wires to each sensor.

Simplify

As mentioned before, the ECU supports analog and digital I/O. Any more advanced interfaces, such as UART or I2C cannot be integrated natively. Many of the sensors implemented on the car (e.g. IMU, IR temperature sensors, etc.) only support a higher-level digital interface. Some sort of module would then be required either way in order to use those sensors on the vehicle.

Having generic modules that could be implemented anywhere on the car, with minimal wiring, greatly simplifies the process of adding any arbitrary sensor, as opposed to making a custom module per sensor.

Features

The boards use a dsPIC33EV family microcontroller, programmed in bare-metal C. The boards feature:

• 5 dedicated analog inputs
• I2C breakout with optional buffer
• CAN bus interface
• Breakout of all unused MCU pins
• CAN termination switch
• BOM variant between central module with IMU and wheel module with IR brake temperature sensors

Gallery