CAN Bus Transceiver

#include "driver/twai.h"

// Define the GPIO pins connected to the CAN G-Mod TX and RX pins
#define CAN_TX_PIN  5  // Connected to CAN G-Mod TX
#define CAN_RX_PIN  4  // Connected to CAN G-Mod RX

void setup() {
  Serial.begin(115200);
  while (!Serial);

  Serial.println("Starting CAN Bus Transceiver Example...");

  // Configure TWAI (CAN) controller at 500 kbps
  twai_general_config_t g_config = TWAI_GENERAL_CONFIG_DEFAULT(
    (gpio_num_t)CAN_TX_PIN, 
    (gpio_num_t)CAN_RX_PIN, 
    TWAI_MODE_NORMAL
  );
  twai_timing_config_t t_config = TWAI_TIMING_CONFIG_500KBITS();
  twai_filter_config_t f_config = TWAI_FILTER_CONFIG_ACCEPT_ALL();

  // Install and start TWAI driver
  if (twai_driver_install(&g_config, &t_config, &f_config) != ESP_OK) {
    Serial.println("Failed to install TWAI driver!");
    return;
  }

  if (twai_start() != ESP_OK) {
    Serial.println("Failed to start TWAI driver!");
    return;
  }

  Serial.println("CAN Driver successfully initialized at 500 kbps.");
}

void loop() {
  // --- 1. Transmit a CAN Message ---
  twai_message_t tx_msg;
  tx_msg.identifier = 0x123;         // Standard 11-bit CAN ID
  tx_msg.flags = TWAI_MSG_FLAG_NONE;
  tx_msg.data_length_code = 4;
  tx_msg.data[0] = 0x10;
  tx_msg.data[1] = 0x20;
  tx_msg.data[2] = 0x30;
  tx_msg.data[3] = 0x40;

  if (twai_transmit(&tx_msg, pdMS_TO_TICKS(100)) == ESP_OK) {
    Serial.println("Sent CAN frame ID: 0x123");
  } else {
    Serial.println("Transmit timed out or bus busy");
  }

  // --- 2. Check for Incoming CAN Messages ---
  twai_message_t rx_msg;
  if (twai_receive(&rx_msg, pdMS_TO_TICKS(500)) == ESP_OK) {
    Serial.printf("Received Frame from 0x%03X [DLC %d]: ", rx_msg.identifier, rx_msg.data_length_code);
    for (int i = 0; i < rx_msg.data_length_code; i++) {
      Serial.printf("0x%02X ", rx_msg.data[i]);
    }
    Serial.println();
  }

  delay(1000);
}