Initial push - gps needs to be implemented in sender

LoRaReceiver/LoRaReceiver.ino

@@ -0,0 +1,101 @@
+#include <SPI.h>
+#include <LoRa.h>
+
+#define SYNC_WORD 0xCE
+#define SENDER_ID 0xAA
+#define SELF_ID 0xAB
+
+#define LORA_SCK 5
+#define LORA_MISO 19
+#define LORA_MOSI 27
+#define LORA_CS 18
+#define LORA_RST 23
+#define LORA_IRQ 26
+#define LORA_FREQ 868E6
+
+void sendMessage(const String& msg) {
+  LoRa.beginPacket();
+  LoRa.write(SYNC_WORD);
+  LoRa.write(SELF_ID);
+  LoRa.write(msg.length());
+  LoRa.print(msg);
+  LoRa.endPacket(true);
+}
+
+bool receiveMessage(String& out) {
+  int packetSize = LoRa.parsePacket();
+  if (!packetSize) return false;
+
+  byte sync = LoRa.read();
+  byte sender = LoRa.read();
+  if (sync != SYNC_WORD || sender != SENDER_ID) {
+    LoRa.flush();
+    return false;
+  }
+
+  byte len = LoRa.read();
+  String data;
+  while (LoRa.available()) data += (char)LoRa.read();
+
+  if (data.length() != len) {
+    out = "ERR: LEN";
+    return true;
+  }
+
+  sendMessage("ACK");
+  out = data;
+  return true;
+}
+
+void printHelp() {
+  Serial.println("g – Standort anfragen\nh – Hilfe");
+}
+
+void handleCommandG(){
+  sendMessage("g");
+  unsigned long t0 = millis();
+  String answer;
+  while (millis() - t0 < 1000) {
+    if (receiveMessage(answer)) {
+      Serial.println(answer);
+      break;
+    }
+    delay(10);
+  }
+  if (millis() - t0 >= 1000) Serial.println("Timeout");
+}
+
+void setup() {
+  Serial.begin(115200);
+  SPI.begin(LORA_SCK, LORA_MISO, LORA_MOSI, LORA_CS);
+  LoRa.setPins(LORA_CS, LORA_RST, LORA_IRQ);
+  if (!LoRa.begin(LORA_FREQ)) {
+    while (true) {
+      Serial.println("Konnte LoRa nicht initialisieren!\nBitte neustarten!");
+      delay(1000);
+    }
+  }
+  LoRa.enableCrc();
+  // LoRa.setSyncWord(SYNC_WORD); // this would have been simpler nevermind
+}
+
+void loop() {
+  if (Serial.available()) {
+    char cmd = Serial.read();
+    switch (cmd) {
+      case 'h':
+        printHelp();
+        break;
+      case 'g':
+        handleCommandG();
+        break;
+      default:
+        printHelp();
+        break;
+    }
+  }
+
+  // passive listening
+  String msg;
+  if (receiveMessage(msg)) Serial.printf("RX: %s\n", msg.c_str());
+}

LoRaSender/LoRaSender.ino

@@ -0,0 +1,89 @@
+#include <SPI.h>
+#include <LoRa.h>
+
+#define SYNC_WORD 0xCE
+#define DEST_ID 0xAB  // receiver
+#define SELF_ID 0xAA  // sender
+
+#define LORA_SCK 5
+#define LORA_MISO 19
+#define LORA_MOSI 27
+#define LORA_CS 18
+#define LORA_RST 23
+#define LORA_IRQ 26
+#define LORA_FREQ 868E6
+
+void sendMessage(const String& msg) {
+  LoRa.beginPacket();
+  LoRa.write(DEST_ID);
+  LoRa.write(SELF_ID);
+  LoRa.write(msg.length());
+  LoRa.print(msg);
+  LoRa.endPacket(true);
+}
+
+bool waitForPacket(unsigned long timeout_ms) {
+  unsigned long t0 = millis();
+  while (millis() - t0 < timeout_ms) {
+    if (LoRa.parsePacket()) return true;
+    delay(5);
+  }
+  return false;  // Timeout
+}
+
+bool getPacket(String& payload, byte& sender) {
+  int size = LoRa.parsePacket();
+  if (!size) return false;
+
+  byte dest = LoRa.read();
+  sender = LoRa.read();
+  byte len = LoRa.read();
+
+  if (dest != SELF_ID && dest != 0xFF) {
+    LoRa.flush();
+    return false;
+  }
+
+  while (LoRa.available()) payload += (char)LoRa.read();
+  return (payload.length() == len);
+}
+
+bool waitForAck(unsigned long timeout_ms = 1000) {
+  if (!waitForPacket(timeout_ms)) return false;
+  String payload;
+  byte snd;
+  if (!getPacket(payload, snd)) return false;
+  return (snd == DEST_ID && payload == "ACK");
+}
+
+String readGpsLine() {
+  return "48.12345,11.56789";
+}
+
+void setup() {
+  Serial.begin(115200);
+
+  SPI.begin(LORA_SCK, LORA_MISO, LORA_MOSI, LORA_CS);
+  LoRa.setPins(LORA_CS, LORA_RST, LORA_IRQ);
+  if (!LoRa.begin(LORA_FREQ))
+    while (true)
+      ;
+
+  LoRa.setSyncWord(SYNC_WORD);
+  LoRa.enableCrc();
+}
+
+void loop() {
+  if (waitForPacket(10)) {
+    String cmd;
+    byte snd;
+    if (!getPacket(cmd, snd)) return;
+
+    if (snd == DEST_ID && cmd == "g") {
+      String gps = readGpsLine();
+      sendMessage(gps);
+
+      if (!waitForAck()) Serial.println("ACK fehlte!");
+    }
+  }
+}