CANLIB

All of the subprojects of Waterloo Rocketry's CAN bus project need the ability to communicate over CAN. This repository contains the library that all of them use in order to do so.

At present, this library is primarily only useful for developing new subsystems for Waterloo Rocketry's CAN bus system. However, all of the code is released under GPL, so if you want to adapt any of it for your own project, go nuts.

RocketCAN

RocketCAN is Waterloo Rocketry's project to network several independent electrical systems onboard our rocket together over a CAN bus. The goal is to encourage separation of concerns of different subsystems, and to decrease the complexity of adding additional functionality to the rocket in the future.

For example, several systems onboard the rocket need the ability to communicate with the ground station before and during flight. Instead of equipping every subsystem with its own radio transceiver, we have a single board responsible for all radio communications. All CAN networked systems can send and receive radio data through it.

At present, there are 8 independent systems that can communicate over this CAN bus. The PCB designs for each can be found at this repository. The software, as well as README descriptions for each subsystem are developed in the following independent repositories:

• Radio Subsystem
• Logging Subsystem
• Nitrous Vent Valve Subsystem
• Injector Valve Subsystem
• Sensor Suite Subsystem
• Arming Subsystem
• Oxidizer Fill Sensing Subsystem
• Telemetry Subsystem

Supported Platforms

The canlib library is designed to run on all CAN subsystems. All of those systems run on one of three CAN modules, so those are the three that we currently support:

1. PIC18F26K83: the cheap, low powered 8 bit microcontroller that the majority of the subsystems run on. The platform specific code for this microcontroller is found in pic18f26k83/. It is meant to be compiled with Microchip's XC8 compiler.
2. DSPIC33EP512GP502: A higher powered 16 bit digital signal processing microcontroller that the logging and sensor subsystems run on. The platform specific code for this microcontroller is found in dspic33epxxxgp50x/. It is meant to be compiled with Microchip's XC16 compiler.
3. MCP2515: A standalone CAN module that interfaces with a host microcontroller over SPI. This module should be useable with any microcontroller, as long as it supports SPI. This code is found int mcp2515/, and should be buildable by any compiler.

Minimum Viable Setup

To see a minimum viable program for each of these platforms, look in the tests/ directory. There is a MPLAB project for each platform which contains the required initialization code that needs to be run by any project using canlib on that platform. Each should also show how CAN messages can be sent on that platform.

Utilities

The util/ directory contains some platform independent utilities that may be helpful in some instances. Each utility module is described separately:

timing_util

This module contains some preset can_timing_params for the bitrate that the library is currently running at. At present, all canlib devices run a CAN bit time of 24us (4.16 kHz). To initialize a can_timings_t, call can_generate_timing_params with the frequency that the CAN module is running at. In most instances, this will be the same frequency as the microcontroller core, but can vary depending on project setup. All functions are described in util/timing_util.h.

can_rcv_buffer

This module contains a thread safe ring buffer that can be populated with incoming CAN messages during the CAN ISR, which can later be read out by the application main thread. The module must be initialized with an external memory pool. All functions in this module are described in util/can_rcv_buffer.h.

Timing Functions

Canlib supports a timer module for the pic18f26k83, which allows the use of a millis() function that returns the time in ms since the timer0_init() function is called. In order for this module to run, timer0_handle_interupt() must be called when the timer 0 interupt flag, PIR3bits.TMR0IF is set.

IMPORTANT: The timer0_handle_interupt() function DOES NOT CLEAR the PIR3bits.TMR0IF interupt flag. This is the responsiblity of the top level ISR!

REMINDER: This will take over timer0, do not use timer0 if using this module. All functions in this module are described in pic18f26k83/pic18f26k83_timer.h.