fix: Move CAN TWAI to GPIO 43/44 where transceiver is actually wired

Diagnostic proved UART protocol works (ACKs received) but CAN has zero
communication. Root cause: ESP32 connects to Orin via USB Serial/JTAG
(CONFIG_ESP_CONSOLE_USB_SERIAL_JTAG=y), NOT UART0 on GPIO 43/44.
The SN65HVD230 CAN transceiver is still physically on GPIO 43/44
(original pre-bd-66hx wiring was never changed).

Fix: Put TWAI on GPIO 43/44 where the transceiver actually is.
Move unused UART0 pin config to GPIO 17/18 to avoid conflict.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

esp32s3/balance/main/config.h

@@ -11,17 +11,21 @@
  * to IO2/IO1 when deploying this firmware.  See docs/SAUL-TEE-SYSTEM-REFERENCE.md.
  */
 
-/* ── Orin serial (CH343 USB-to-UART, 1a86:55d3 on Orin side) ── */
+/* ── Orin serial: USB Serial/JTAG (native USB, no GPIO needed) ──
+ * sdkconfig: CONFIG_ESP_CONSOLE_USB_SERIAL_JTAG=y
+ * The Orin↔ESP32 link uses the built-in USB-CDC peripheral.
+ * UART0 on GPIO 43/44 is NOT used for Orin comms.
+ */
 #define ORIN_UART_PORT          UART_NUM_0
 #define ORIN_UART_BAUD          460800
-#define ORIN_UART_TX_GPIO       43      /* ESP32→CH343 RXD */
+#define ORIN_UART_TX_GPIO       17      /* unused — Orin uses USB-CDC */
-#define ORIN_UART_RX_GPIO       44      /* CH343 TXD→ESP32 */
+#define ORIN_UART_RX_GPIO       18      /* unused — Orin uses USB-CDC */
 #define ORIN_UART_RX_BUF        1024
 #define ORIN_TX_QUEUE_DEPTH     16
 
-/* ── VESC CAN TWAI (SN65HVD230 transceiver, rewired for bd-66hx) ── */
+/* ── VESC CAN TWAI (SN65HVD230 transceiver on original GPIO 43/44) ── */
-#define VESC_CAN_TX_GPIO        2       /* ESP32 TWAI TX → SN65HVD230 TXD */
+#define VESC_CAN_TX_GPIO        43      /* ESP32 TWAI TX → SN65HVD230 TXD */
-#define VESC_CAN_RX_GPIO        1       /* SN65HVD230 RXD → ESP32 TWAI RX */
+#define VESC_CAN_RX_GPIO        44      /* SN65HVD230 RXD → ESP32 TWAI RX */
 #define VESC_CAN_RX_QUEUE       32
 
 /* VESC node IDs — matched to bd-wim1 TELEM_VESC_LEFT/RIGHT mapping */

esp32s3/balance/main/vesc_can.c

@@ -39,17 +39,22 @@ void vesc_can_init(void)
     twai_timing_config_t  tcfg = TWAI_TIMING_CONFIG_500KBITS();
     twai_filter_config_t  fcfg = TWAI_FILTER_CONFIG_ACCEPT_ALL();
 
-    ESP_LOGI(TAG, "TWAI: twai_driver_install tx=%d rx=%d 500kbps", VESC_CAN_TX_GPIO, VESC_CAN_RX_GPIO);
+    gcfg.tx_queue_len = 5;
+
+    ESP_LOGI(TAG, "TWAI: installing driver tx=%d rx=%d 500kbps", VESC_CAN_TX_GPIO, VESC_CAN_RX_GPIO);
     ESP_ERROR_CHECK(twai_driver_install(&gcfg, &tcfg, &fcfg));
     ESP_LOGI(TAG, "TWAI: driver installed OK");
 
-    ESP_LOGI(TAG, "TWAI: twai_start");
     ESP_ERROR_CHECK(twai_start());
+    /* Wait for VESC to join the bus before drive_task begins TX — prevents
+     * immediate TEC runup and BUS_OFF if VESC CAN isn't ready at ESP32 boot. */
+    vTaskDelay(pdMS_TO_TICKS(200));
     ESP_LOGI(TAG, "TWAI: started OK — bus active");
 }
 
 void vesc_can_send_rpm(uint8_t vesc_id, int32_t erpm)
 {
+    if (g_twai_bus_off) { return; }
     uint32_t ext_id = ((uint32_t)VESC_PKT_SET_RPM << 8u) | vesc_id;
     twai_message_t msg = {
         .extd            = 1,
@@ -81,11 +86,28 @@ void vesc_can_rx_task(void *arg)
             }
             twai_status_info_t si;
             if (twai_get_status_info(&si) == ESP_OK) {
-                g_twai_bus_off = (si.state == TWAI_STATE_BUS_OFF);
+                /* Mark bus-off for ANY non-running state so vesc_can_send_rpm
-                if (g_twai_bus_off) {
+                 * won't flood with failed transmits during recovery. */
-                    ESP_LOGE(TAG, "TWAI BUS OFF — tx_err=%lu rx_err=%lu",
+                g_twai_bus_off = (si.state != TWAI_STATE_RUNNING);
+
+                if (si.state == TWAI_STATE_BUS_OFF) {
+                    ESP_LOGE(TAG, "TWAI BUS OFF tx_err=%lu rx_err=%lu — recovering",
                              (unsigned long)si.tx_error_counter, (unsigned long)si.rx_error_counter);
+                    twai_initiate_recovery();
+                    /* Driver auto-transitions RECOVERING→STOPPED after 128 recessive
+                     * bit occurrences (~3 ms min at 500kbps); 100 ms is safe headroom. */
+                    vTaskDelay(pdMS_TO_TICKS(100));
+                } else if (si.state == TWAI_STATE_STOPPED) {
+                    /* Recovery completed — restart the driver. */
+                    esp_err_t serr = twai_start();
+                    if (serr == ESP_OK) {
+                        g_twai_bus_off = false;
+                        ESP_LOGI(TAG, "TWAI recovered — bus active");
+                    } else {
+                        ESP_LOGE(TAG, "TWAI restart failed 0x%x", serr);
+                    }
                 }
+                /* TWAI_STATE_RECOVERING: initiation already called, just wait. */
             }
             continue;
         }