[esp32_can] Add listen-only mode to esp32_can component (#13084)

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

esphome/components/esp32_can/canbus.py

@@ -19,6 +19,7 @@ from esphome.components.esp32 import (
 import esphome.config_validation as cv
 from esphome.const import (
     CONF_ID,
+    CONF_MODE,
     CONF_RX_PIN,
     CONF_RX_QUEUE_LEN,
     CONF_TX_PIN,
@@ -33,6 +34,13 @@ CONF_TX_ENQUEUE_TIMEOUT = "tx_enqueue_timeout"
 esp32_can_ns = cg.esphome_ns.namespace("esp32_can")
 esp32_can = esp32_can_ns.class_("ESP32Can", CanbusComponent)
 
+# Mode options - consistent with MCP2515 component
+CanMode = esp32_can_ns.enum("CanMode")
+CAN_MODES = {
+    "NORMAL": CanMode.CAN_MODE_NORMAL,
+    "LISTENONLY": CanMode.CAN_MODE_LISTEN_ONLY,
+}
+
 # Currently the driver only supports a subset of the bit rates defined in canbus
 # The supported bit rates differ between ESP32 variants.
 # See ESP-IDF Programming Guide --> API Reference --> Two-Wire Automotive Interface (TWAI)
@@ -95,6 +103,7 @@ CONFIG_SCHEMA = canbus.CANBUS_SCHEMA.extend(
         cv.Optional(CONF_BIT_RATE, default="125KBPS"): validate_bit_rate,
         cv.Required(CONF_RX_PIN): pins.internal_gpio_input_pin_number,
         cv.Required(CONF_TX_PIN): pins.internal_gpio_output_pin_number,
+        cv.Optional(CONF_MODE, default="NORMAL"): cv.enum(CAN_MODES, upper=True),
         cv.Optional(CONF_RX_QUEUE_LEN): cv.uint32_t,
         cv.Optional(CONF_TX_QUEUE_LEN): cv.uint32_t,
         cv.Optional(CONF_TX_ENQUEUE_TIMEOUT): cv.positive_time_period_milliseconds,
@@ -117,6 +126,7 @@ async def to_code(config):
 
     cg.add(var.set_rx(config[CONF_RX_PIN]))
     cg.add(var.set_tx(config[CONF_TX_PIN]))
+    cg.add(var.set_mode(config[CONF_MODE]))
     if (rx_queue_len := config.get(CONF_RX_QUEUE_LEN)) is not None:
         cg.add(var.set_rx_queue_len(rx_queue_len))
     if (tx_queue_len := config.get(CONF_TX_QUEUE_LEN)) is not None:

esphome/components/esp32_can/esp32_can.cpp

@@ -75,8 +75,15 @@ bool ESP32Can::setup_internal() {
     return false;
   }
 
+  // Select TWAI mode based on configuration
+  twai_mode_t twai_mode = (this->mode_ == CAN_MODE_LISTEN_ONLY) ? TWAI_MODE_LISTEN_ONLY : TWAI_MODE_NORMAL;
+
+  if (this->mode_ == CAN_MODE_LISTEN_ONLY) {
+    ESP_LOGI(TAG, "CAN bus configured in LISTEN_ONLY mode (passive, no ACKs)");
+  }
+
   twai_general_config_t g_config =
-      TWAI_GENERAL_CONFIG_DEFAULT((gpio_num_t) this->tx_, (gpio_num_t) this->rx_, TWAI_MODE_NORMAL);
+      TWAI_GENERAL_CONFIG_DEFAULT((gpio_num_t) this->tx_, (gpio_num_t) this->rx_, twai_mode);
   g_config.controller_id = next_twai_ctrl_num++;
   if (this->tx_queue_len_.has_value()) {
     g_config.tx_queue_len = this->tx_queue_len_.value();
@@ -111,6 +118,12 @@ bool ESP32Can::setup_internal() {
 }
 
 canbus::Error ESP32Can::send_message(struct canbus::CanFrame *frame) {
+  // In listen-only mode, we cannot transmit
+  if (this->mode_ == CAN_MODE_LISTEN_ONLY) {
+    ESP_LOGW(TAG, "Cannot send messages in LISTEN_ONLY mode");
+    return canbus::ERROR_FAIL;
+  }
+
   if (this->twai_handle_ == nullptr) {
     // not setup yet or setup failed
     return canbus::ERROR_FAIL;

esphome/components/esp32_can/esp32_can.h

@@ -10,10 +10,16 @@
 namespace esphome {
 namespace esp32_can {
 
+enum CanMode : uint8_t {
+  CAN_MODE_NORMAL = 0,
+  CAN_MODE_LISTEN_ONLY = 1,
+};
+
 class ESP32Can : public canbus::Canbus {
  public:
   void set_rx(int rx) { rx_ = rx; }
   void set_tx(int tx) { tx_ = tx; }
+  void set_mode(CanMode mode) { mode_ = mode; }
   void set_tx_queue_len(uint32_t tx_queue_len) { this->tx_queue_len_ = tx_queue_len; }
   void set_rx_queue_len(uint32_t rx_queue_len) { this->rx_queue_len_ = rx_queue_len; }
   void set_tx_enqueue_timeout_ms(uint32_t tx_enqueue_timeout_ms) {
@@ -28,6 +34,7 @@ class ESP32Can : public canbus::Canbus {
 
   int rx_{-1};
   int tx_{-1};
+  CanMode mode_{CAN_MODE_NORMAL};
   TickType_t tx_enqueue_timeout_ticks_{};
   optional<uint32_t> tx_queue_len_{};
   optional<uint32_t> rx_queue_len_{};

tests/components/esp32_can/common.yaml

@@ -18,6 +18,7 @@ canbus:
     tx_pin: ${tx_pin}
     can_id: 4
     bit_rate: 50kbps
+    mode: NORMAL
     on_frame:
       - can_id: 500
         then:

tests/components/esp32_can/test.esp32-c6-idf.yaml

@@ -12,17 +12,7 @@ esphome:
           canbus_id: esp32_internal_can
           can_id: 0x100
           data: [0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08]
-      - canbus.send:
-          # Extended ID explicit
-          canbus_id: esp32_internal_can_2
-          use_extended_id: true
-          can_id: 0x100
-          data: [0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08]
-      - canbus.send:
-          # Standard ID by default
-          canbus_id: esp32_internal_can_2
-          can_id: 0x100
-          data: [0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08]
+      # Note: esp32_internal_can_2 uses LISTENONLY mode, so no send actions
 
 canbus:
   - platform: esp32_can
@@ -31,6 +21,7 @@ canbus:
     tx_pin: GPIO7
     can_id: 4
     bit_rate: 50kbps
+    mode: NORMAL
     on_frame:
       - can_id: 500
         then:
@@ -62,6 +53,7 @@ canbus:
     tx_pin: GPIO9
     can_id: 4
     bit_rate: 50kbps
+    mode: LISTENONLY
     on_frame:
       - can_id: 500
         then: