Handle INIT messages and add set_init_handler() callback

CMRI.cpp

@@ -35,6 +35,8 @@ CMRI::CMRI(unsigned int address, unsigned int input_bits, unsigned int output_bi
 	// set state
 , _rx_buffer((char *) malloc(_rx_length))
 , _tx_buffer((char *) malloc(_tx_length))
+, _rx_data_len(0)
+, _init_handler(nullptr)
 
 , _serial(serial_class)
 
@@ -55,6 +57,11 @@ void CMRI::set_address(unsigned int address)
 	_address = address;
 }
 
+void CMRI::set_init_handler(void (*handler)(const uint8_t *, int))
+{
+	_init_handler = handler;
+}
+
 // reads in serial data, decodes packets
 // automatically responds to POLL requests
 // returns packet type so if we got a SET request you know to update your outputs
@@ -72,19 +79,23 @@ bool CMRI::process()
 
 bool CMRI::process_char(char c)
 {
-	// if it's a SET that's fine do nothing
-	// if it's an INIT that's also fine, we don't really care
-	// if it's a GET, well, do nothing since it must be someone else replying
-	// if it's a POLL then reply straight away with our data
-	switch (_decode(c))
+	// if it's a SET, update the output buffer
+	// if it's an INIT, the payload was consumed and the sketch can handle it
+	// if it's a GET, ignore — must be another node replying
+	// if it's a POLL, reply straight away with our input data
+	unsigned char ret = _decode(c);
+	switch (ret)
 	{
 		case POLL:
 			transmit();
 			return true;
-		
+
 		case SET:
+		case INIT:
+			if (ret == INIT && _init_handler)
+				_init_handler((const uint8_t *)_rx_buffer, _rx_data_len);
 			return true;
-		
+
 		default:
 			return false;
 	}
@@ -192,8 +203,11 @@ uint8_t CMRI::_decode(uint8_t c)
 			break;
 
 		case DECODE_CMD:
+            _rx_packet_type = c;
 			if (c == SET)
 				_mode = DECODE_DATA;
+            else if (c == INIT)
+     			_mode = DECODE_DATA;
 			else if (c == POLL)
 				goto POSTAMBLE_POLL;
 			else
@@ -241,8 +255,10 @@ uint8_t CMRI::_decode(uint8_t c)
 	return NOOP;
 
 POSTAMBLE_SET:
+		_rx_data_len = _rx_index;
 		_mode = PREAMBLE_1;
-		return SET;
+		_rx_index = 0;
+		return _rx_packet_type;
 
 POSTAMBLE_POLL:
 		_mode = PREAMBLE_1;

CMRI.h

@@ -34,6 +34,7 @@ class CMRI
 	public:
 		CMRI(unsigned int address = 0, unsigned int input_bits = 24, unsigned int output_bits = 48, Stream& serial_class = Serial);
 		void set_address(unsigned int address);
+		void set_init_handler(void (*handler)(const uint8_t *data, int len));
 
 		bool process();
 		bool process_char(char c);
@@ -66,6 +67,8 @@ class CMRI
 		char	_rx_packet_type;
 		char* _rx_buffer;
 		char* _tx_buffer;
+		int   _rx_data_len;
+		void (*_init_handler)(const uint8_t *, int);
 
 		Stream& _serial;
 

examples/init_handler/init_handler.ino

@@ -0,0 +1,72 @@
+/**
+ * C/MRI INIT handler example
+ * ===========================
+ * Demonstrates how to register an INIT callback to inspect the
+ * configuration payload sent by JMRI at startup.
+ *
+ * The INIT message body follows NMRA LCS-9.10.1:
+ *   byte 0:   NDP (Node Definition Parameter)
+ *   bytes 1-2: DLH/DLL (transmit delay, high & low bytes)
+ *   bytes 3+:  node-type-specific options
+ *
+ * The transmit delay is computed as (DLH * 256 + DLL) * 10 microseconds.
+ * This example reads the delay and prints the configuration to Serial.
+ *
+ * To set up in JMRI:
+ * 1: Create a new C/MRI connection (Serial, 9600 baud)
+ * 2: Configure a node with address 0 — JMRI sends an INIT at startup
+ * 3: Open Tools > Tables > Lights and add a light at address 1
+ * 4: Open the C/MRI Monitor to watch the INIT message
+ *    Raw format: [41 49 43 00 0A ...] = UA 'A', cmd 'I', NDP='C', DL=10
+ */
+
+#include <CMRI.h>
+
+CMRI cmri; // defaults to a SMINI with address 0
+
+// ---------------------------------------------------------------------------
+// INIT handler callback
+// Called automatically when an INIT ('I') packet is received.
+// data  – pointer to the raw INIT payload bytes
+// len   – number of bytes in the payload
+// ---------------------------------------------------------------------------
+void on_init(const uint8_t *data, int len) {
+  Serial.print(F("INIT received ("));
+
+  if (len >= 1) {
+    Serial.print(F("NDP="));
+    Serial.write(data[0]);
+    Serial.print(F(" "));
+  }
+
+  if (len >= 3) {
+    int delay_us = (data[1] * 256 + data[2]) * 10;
+    Serial.print(F("DL="));
+    Serial.print(delay_us);
+    Serial.print(F("us "));
+  }
+
+  if (len > 3) {
+    Serial.print(F("options="));
+    for (int i = 3; i < len; i++) {
+      if (i > 3) Serial.print(F(" "));
+      if (data[i] < 16) Serial.print(F("0"));
+      Serial.print(data[i], HEX);
+    }
+    Serial.print(F(" "));
+  }
+
+  Serial.print(len);
+  Serial.println(F(" bytes"));
+}
+
+void setup() {
+  Serial.begin(9600, SERIAL_8N2);
+  cmri.set_init_handler(on_init);
+  pinMode(13, OUTPUT);
+}
+
+void loop() {
+  cmri.process();
+  digitalWrite(13, cmri.get_bit(0));
+}