From 3cfbb0cf58c3e85ad3299f3f3a837c85eb70fb0e Mon Sep 17 00:00:00 2001
From: Mark Qvist <mark@unsigned.io>
Date: Fri, 12 Mar 2021 18:48:50 +0100
Subject: [PATCH] Added implicit header mode

---
 Config.h           | 12 +++++++-----
 Framing.h          |  1 +
 RNode_Firmware.ino | 26 ++++++++++++++++++++++----
 Utilities.h        | 17 ++++++++++++++++-
 4 files changed, 46 insertions(+), 10 deletions(-)

diff --git a/Config.h b/Config.h
index 7ae3d00..179ead6 100644
--- a/Config.h
+++ b/Config.h
@@ -4,7 +4,7 @@
 	#define CONFIG_H
 
 	#define MAJ_VERS  0x01
-	#define MIN_VERS  0x10
+	#define MIN_VERS  0x11
 
 	#define MCU_1284P 0x91
 
@@ -61,10 +61,12 @@
 	uint32_t lora_freq = 0;
 
 	// Operational variables
-	bool radio_locked = true;
-	bool radio_online = false;
-	bool hw_ready     = false;
-	bool promisc      = false;
+	bool radio_locked  = true;
+	bool radio_online  = false;
+	bool hw_ready      = false;
+	bool promisc       = false;
+	bool implicit      = false;
+	uint8_t implicit_l = 0;
 
 	uint8_t op_mode   = MODE_HOST;
 	uint8_t model     = 0x00;
diff --git a/Framing.h b/Framing.h
index 80ec1cd..7290167 100644
--- a/Framing.h
+++ b/Framing.h
@@ -16,6 +16,7 @@
 	#define CMD_RADIO_STATE 0x06
 	#define CMD_RADIO_LOCK	0x07
 	#define CMD_DETECT		0x08
+	#define CMD_IMPLICIT	0x09
 	#define CMD_PROMISC		0x0E
 	#define CMD_READY		0x0F
 
diff --git a/RNode_Firmware.ino b/RNode_Firmware.ino
index bca73d7..d7a562e 100644
--- a/RNode_Firmware.ino
+++ b/RNode_Firmware.ino
@@ -58,6 +58,14 @@ void setup() {
   validateStatus();
 }
 
+void lora_receive() {
+  if (!implicit) {
+    LoRa.receive();
+  } else {
+    LoRa.receive(implicit_l);
+  }
+}
+
 bool startRadio() {
   update_radio_lock();
   if (!radio_online) {
@@ -80,7 +88,7 @@ bool startRadio() {
         LoRa.enableCrc();
         LoRa.onReceive(receiveCallback);
 
-        LoRa.receive();
+        lora_receive();
 
         // Flash an info pattern to indicate
         // that the radio is now on
@@ -275,7 +283,7 @@ void transmit(size_t size) {
       LoRa.endPacket();
       led_tx_off();
 
-      LoRa.receive();
+      lora_receive();
     } else {
       // In promiscuous mode, we only send out
       // plain raw LoRa packets with a maximum
@@ -288,7 +296,14 @@ void transmit(size_t size) {
         size = SINGLE_MTU;
       }
 
-      LoRa.beginPacket();
+      // If implicit header mode has been set,
+      // set packet length to payload data length
+      if (!implicit) {
+        LoRa.beginPacket();
+      } else {
+        LoRa.beginPacket(size);
+      }
+
       for (size_t i; i < size; i++) {
         LoRa.write(tbuf[i]);
 
@@ -297,7 +312,7 @@ void transmit(size_t size) {
       LoRa.endPacket();
       led_tx_off();
 
-      LoRa.receive();
+      lora_receive();
     }
   } else {
     kiss_indicate_error(ERROR_TXFAILED);
@@ -435,6 +450,9 @@ void serialCallback(uint8_t sbyte) {
         if (op_mode == MODE_HOST) setCodingRate();
         kiss_indicate_codingrate();
       }
+    } else if (command == CMD_IMPLICIT) {
+      set_implicit_length(sbyte);
+      kiss_indicate_implicit_length();
     } else if (command == CMD_RADIO_STATE) {
       if (sbyte == 0xFF) {
         kiss_indicate_radiostate();
diff --git a/Utilities.h b/Utilities.h
index 73edc79..5c52b53 100644
--- a/Utilities.h
+++ b/Utilities.h
@@ -167,6 +167,13 @@ void kiss_indicate_codingrate() {
 	Serial.write(FEND);
 }
 
+void kiss_indicate_implicit_length() {
+	Serial.write(FEND);
+	Serial.write(CMD_IMPLICIT);
+	Serial.write(implicit_l);
+	Serial.write(FEND);
+}
+
 void kiss_indicate_txpower() {
 	Serial.write(FEND);
 	Serial.write(CMD_TXPOWER);
@@ -263,6 +270,15 @@ void setCodingRate() {
 	if (radio_online) LoRa.setCodingRate4(lora_cr);
 }
 
+void set_implicit_length(uint8_t len) {
+	implicit_l = len;
+	if (implicit_l != 0) {
+		implicit = true;
+	} else {
+		implicit = false;
+	}
+}
+
 void setTXPower() {
 	if (radio_online) {
 		if (model == MODEL_A4) LoRa.setTxPower(lora_txp, PA_OUTPUT_RFO_PIN);
@@ -626,4 +642,3 @@ inline void fifo16_init(FIFOBuffer16 *f, size_t *buffer, size_t size) {
 inline size_t fifo16_len(FIFOBuffer16 *f) {
   return (f->end - f->begin);
 }
-