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CVC Project Overview

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Leina McDermott edited this page Nov 9, 2019 · 5 revisions

What is the CVC?

The CVC is a central computer that primarily determines the vehicle’s powertrain output and monitors its complex safety- critical systems.

Firmware Functional Overview

The CVC firmware is the C program that runs on the STM32F7 microcontroller (MCU), which interfaces with the other hardware on the board to provide the desired functionality of the CVC. The program functions as a state machine that executes the vehicle’s start-up sequence and fault handling. The MCU’s SPI and CAN hardware drivers allow the program to send and receive data to/from the vehicle. The CVC also logs data to an SD card through the SDIO peripheral. The program uses FreeRTOS, an open-source real-time operating system kernel, to schedule tasks and meet its strict timing requirements.

Architecture

The firmware functions on several levels to operate the CVC:

  • Driver Layer: hardware drivers send and receive data to/from the vehicle through the MCU’s peripherals (SPI, CAN, SDIO, I2C, ADC, Timer I/Os)
  • Middleware Layer: implements the FreeRTOS operating system, FatFs file system, and USB on-the-go protocol
  • CVC API: implements CVC-specific functions and provides a layer of abstraction between the driver and middleware layers and the application layer
  • Application: implements user-specific code that may be modified to add or change features

Driver Layer

The CVC requires drivers for the MCU’s SPI, CAN, SDIO, Analog-to-Digital Converter, and timer I/O peripherals. Each peripheral and its purpose is listed below:

Peripheral Purpose
SPI communication between MCU and 12V discrete I/Os
CAN communicate over CAN to send torque commands and monitor data from drive inverter, BMS, engine ECU, and vehicle sensors
SDIO write data to SD card for data logging
I2C communicate with on-board accelerometer
Analog-to-Digital converter receive analog inputs from vehicle sensors
Timer I/O accept pulse-train inputs from wheel-speed sensors; generate PWM output to control servo motor for engine throttle control

ST provides drivers for the STM32F7 MCU in the Hardware Abstraction Layer (HAL) and Low Layer (LL) APIs of the STM32 Cube library.

Middleware Layer

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