feat(firmware): BNO085 node, concentrador y listener PGN 127237

AR_electronics — AR-Autopilot Project

Tarea #3 — firmware/ar_bno085_node_v1/
  Nodo compacto ESP32+CAN lee heading y yaw rate del BNO085 via I2C
  y los publica en el backbone NMEA 2000 como PGN 127250+127251 a 10 Hz.

Tarea #4 — firmware/ar_concentrador_v1/
  Gateway NMEA2000<->NMEA0183 con 4 puertos OUT (UART1 TX broadcast)
  y 4 puertos IN (UART2 RX comandos). Parsea sentencias $PARP, gestiona
  autoridad de mando entre estaciones con timeout 10s y override del puente.
  Reenvía comandos autopilot como PGN 127237 al backbone.

Tarea #5 — nmea2000_consumer (ar_autopilot_v1)
  Listener PGN 127237 entrante desde concentrador:
  HeadingControlSnapshot, HandleHeadingControl() con filtro source address,
  nmea2000_htc() publico, ventana stale 3s para comandos externos.

firmware/ar_concentrador_v1/src/protocols/nmea0183_parser.cpp

@@ -0,0 +1,93 @@
+// =============================================================================
+//  protocols/nmea0183_parser.cpp -- $PARP sentence parser
+// =============================================================================
+
+#include "nmea0183_parser.h"
+
+#include <cstring>
+#include <cstdio>
+#include <cstdlib>
+#include <Arduino.h>
+
+namespace arconcentrador::protocols {
+
+// ---------------------------------------------------------------------------
+uint8_t nmea_checksum(const char* sentence) {
+    // Find content between '$' and '*'
+    const char* start = strchr(sentence, '$');
+    if (!start) return 0xFF;
+    start++;  // skip '$'
+    const char* end = strchr(start, '*');
+    if (!end) return 0xFF;
+    uint8_t crc = 0;
+    for (const char* p = start; p < end; ++p) crc ^= (uint8_t)*p;
+    return crc;
+}
+
+// ---------------------------------------------------------------------------
+ParpCommand parp_parse(const char* sentence) {
+    ParpCommand result{};
+    result.valid = false;
+
+    // Must start with $PARP,
+    if (strncmp(sentence, "$PARP,", 6) != 0) return result;
+
+    // Validate checksum
+    const char* star = strchr(sentence, '*');
+    if (!star || strlen(star) < 3) return result;
+    const uint8_t recv_crc  = (uint8_t)strtoul(star + 1, nullptr, 16);
+    const uint8_t calc_crc  = nmea_checksum(sentence);
+    if (recv_crc != calc_crc) {
+        Serial.printf("[PARSER] checksum error: recv=%02X calc=%02X\n",
+                      recv_crc, calc_crc);
+        return result;
+    }
+
+    // Copy body between "$PARP," and '*'
+    char body[128];
+    const char* body_start = sentence + 6;
+    const size_t body_len  = (size_t)(star - body_start);
+    if (body_len == 0 || body_len >= sizeof(body)) return result;
+    memcpy(body, body_start, body_len);
+    body[body_len] = '\0';
+
+    // Tokenize: CMD,VALUE,STATION_ID
+    char* saveptr = nullptr;
+    const char* tok_cmd = strtok_r(body, ",", &saveptr);
+    const char* tok_val = strtok_r(nullptr, ",", &saveptr);
+    const char* tok_sta = strtok_r(nullptr, ",", &saveptr);
+
+    if (!tok_cmd || !tok_val || !tok_sta) return result;
+
+    strncpy(result.cmd, tok_cmd, sizeof(result.cmd) - 1);
+    result.value      = (float)atof(tok_val);
+    result.station_id = (uint8_t)atoi(tok_sta);
+
+    if (result.station_id < 1 || result.station_id > 4) return result;
+
+    result.valid = true;
+    return result;
+}
+
+// ---------------------------------------------------------------------------
+static char s_line_buf[256];
+static size_t s_line_len = 0;
+
+bool parp_feed(char c, ParpCommand& out) {
+    if (c == '$') {
+        // Start of new sentence — reset buffer.
+        s_line_len = 0;
+    }
+    if (s_line_len < sizeof(s_line_buf) - 1) {
+        s_line_buf[s_line_len++] = c;
+    }
+    if (c == '\n') {
+        s_line_buf[s_line_len] = '\0';
+        s_line_len = 0;
+        out = parp_parse(s_line_buf);
+        return out.valid;
+    }
+    return false;
+}
+
+}  // namespace arconcentrador::protocols