Libcanard: Examples, Starters, Tutorials

Applications & Usage Libcanard
2

107-Arduino-UAVCAN is a Arduino library providing a convenient C++ interface for accessing UAVCAN (v1.0-beta) via libcanard. This library works for

  • ArduinoCore-samd: Arduino Zero, MKR 1000, MKR WiFi 1010, Nano 33 IoT, MKR GSM 1400, MKR NB 1500, MKR WAN 1300/1310 :heavy_check_mark:
  • ArduinoCore-mbed: Portenta H7, Nano 33 BLE, Nano RP2040 Connect, Edge Control :heavy_check_mark:
  • arduino-esp32: ESP32 Dev Module, ESP32 Wrover Module, … :heavy_check_mark:

There’s a dedicated thread on this forum for discussing anything related to the library, of course the default GitHub mechanisms of issues and pull requests can also be employed (choose the right medium :wink:).

Here’s a short example of a node publishing a heartbeat using the 107-Arduino-UAVCAN:

/**************************************************************************************
 * INCLUDE
 **************************************************************************************/

#include <SPI.h>

#include <ArduinoUAVCAN.h>
#include <ArduinoMCP2515.h>

/**************************************************************************************
 * CONSTANTS
 **************************************************************************************/

static int const MKRCAN_MCP2515_CS_PIN  = 3;
static int const MKRCAN_MCP2515_INT_PIN = 7;

/**************************************************************************************
 * FUNCTION DECLARATION
 **************************************************************************************/

void spi_select()
{
  digitalWrite(MKRCAN_MCP2515_CS_PIN, LOW);
}

void spi_deselect()
{
  digitalWrite(MKRCAN_MCP2515_CS_PIN, HIGH);
}

uint8_t spi_transfer(uint8_t const data)
{
  return SPI.transfer(data);
}

void onExternalEvent()
{
  mcp2515.onExternalEventHandler();
}

bool transmitCanFrame(uint32_t const id, uint8_t const * data, uint8_t const len)
{
  return mcp2515.transmit(id, data, len);
}

/**************************************************************************************
 * GLOBAL VARIABLES
 **************************************************************************************/

ArduinoMCP2515 mcp2515(spi_select,
                       spi_deselect,
                       spi_transfer,
                       nullptr,
                       nullptr);

ArduinoUAVCAN uavcan(13, micros, transmitCanFrame);

Heartbeat_1_0 hb(0, Heartbeat_1_0::Health::NOMINAL, Heartbeat_1_0::Mode::INITIALIZATION, 0);

/**************************************************************************************
 * SETUP/LOOP
 **************************************************************************************/

void setup()
{
  Serial.begin(9600);
  while(!Serial) { }

  /* Setup SPI access */
  SPI.begin();
  pinMode(MKRCAN_MCP2515_CS_PIN, OUTPUT);
  digitalWrite(MKRCAN_MCP2515_CS_PIN, HIGH);

  /* Attach interrupt handler to register MCP2515 signaled by taking INT low */
  pinMode(MKRCAN_MCP2515_INT_PIN, INPUT_PULLUP);
  attachInterrupt(digitalPinToInterrupt(MKRCAN_MCP2515_INT_PIN), onExternalEvent, FALLING);

  /* Initialize MCP2515 */
  mcp2515.begin();
  mcp2515.setBitRate(CanBitRate::BR_250kBPS);
  mcp2515.setNormalMode();
}

void loop()
{
  /* Update the heartbeat object */
  hb.uptime(millis() / 1000);
  hb.mode(Heartbeat_1_0::Mode::OPERATIONAL);

  /* Publish the heartbeat once/second */
  static unsigned long prev = 0;
  unsigned long const now = millis();
  if(now - prev > 1000) {
    uavcan.publish(hb);
    prev = now;
  }

  /* Transmit all enqeued CAN frames */
  while(uavcan.transmitCanFrame()) { }
}
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