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CAD with backoff process

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Ricardo Guzman (Richonguzman)
2026-06-10 00:25:27 -04:00
parent a97757c0b2
commit 9898e123d2
1 changed files with 24 additions and 30 deletions
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src/lora_utils.cpp
+24 -30
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@@ -27,10 +27,8 @@
#include "display.h"
#include "utils.h"
//
#define DIFS_SLOTS 2 // Number of secuential CAD slots to consider a free channel to Tx
int BO_MAX = 4; // Max Backoff
//
extern Configuration Config;
extern NetworkManager *networkManager;
@@ -65,6 +63,9 @@ bool transmitFlag = true;
int rssi, freqError;
float snr;
#define DIFS_SLOTS 2 // Number of secuential CAD slots to consider a free channel to Tx
int backoffMax = 4; // Max Backoff value (number of CAD slots to wait before Tx)
namespace LoRa_Utils {
@@ -170,19 +171,11 @@ namespace LoRa_Utils {
radio.setBandwidth(signalBandwidth);
}
//
bool doCAD() { // Checks for CAD (Channel Activity Detection)
int state = radio.scanChannel();
if (state == RADIOLIB_LORA_DETECTED) {
return true;
} else if (state == RADIOLIB_CHANNEL_FREE) {
return false;
} else { // CAD failed, return true for safety
return true;
}
bool doCAD() { // CAD (Channel Activity Detection)
return radio.scanChannel() != RADIOLIB_CHANNEL_FREE; // false=channel free | true=RADIOLIB_LORA_DETECTED or CAD failed
}
bool doDIFS() { // DIFS (Distributed Inter-Frame Space) Return True = channel free
bool doDIFS() {
for (uint8_t i = DIFS_SLOTS; i > 0; i--) {
if (doCAD()) return false;
}
@@ -191,12 +184,20 @@ namespace LoRa_Utils {
void waitForDIFS() {
while (!doDIFS()) {
//
Serial.println("DIFS failed, retry");
//
Serial.println("CAD/DIFS failed, retry...");
}
}
void doBEB() {
int backoffCounter = random(1, backoffMax + 1);
while (backoffCounter > 0) {
if (doCAD()) {
waitForDIFS(); // busy channel: freeze backoff and restart DIFS
} else {
backoffCounter--;
}
}
}
//
void sendNewPacket(const String& newPacket) {
if (!Config.loramodule.txActive) return;
@@ -211,17 +212,10 @@ namespace LoRa_Utils {
if (Config.digi.ecoMode != 1) digitalWrite(INTERNAL_LED_PIN, HIGH); // disabled in Ultra Eco Mode
#endif
//
#ifdef HAS_SX1262
if (Config.loramodule.cadActive) {
//
Serial.println("checking for DIFS");
//
waitForDIFS();
//
}
#endif
//
if (Config.loramodule.cadActive) {
waitForDIFS(); // DIFS (Distributed Inter-Frame Space)
doBEB(); // BEB (Binary Exponential Backoff)
}
int state = radio.transmit("\x3c\xff\x01" + newPacket);
transmitFlag = true;