Initial push - gps needs to be implemented in sender

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!");
+    }
+  }
+}