From 30a07a32cecd324c03c04896a63b560cb29d93ca Mon Sep 17 00:00:00 2001
From: Matt Corallo <649246+TheBlueMatt@users.noreply.github.com>
Date: Thu, 26 Sep 2019 22:22:05 +0000
Subject: [PATCH 1/2] Fix RSSI offset for pre-msg RSSI notification

last_rssi is a large negative number, with rssi_offset being +292,
intended to be added to put the value inside the range of a single byte uint.
Before sending the data message, a RSSI message is automatically sent,
which is quite nice, but the value ends up overflowing the 8-bit uint, giving
a bogus value.
---
 RNode_Firmware.ino | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/RNode_Firmware.ino b/RNode_Firmware.ino
index 4928529..6bf3bfb 100644
--- a/RNode_Firmware.ino
+++ b/RNode_Firmware.ino
@@ -144,7 +144,7 @@ void receiveCallback(int packet_size) {
       // recieved packet to the host.
       Serial.write(FEND);
       Serial.write(CMD_STAT_RSSI);
-      Serial.write((uint8_t)(last_rssi-rssi_offset));
+      Serial.write((uint8_t)(last_rssi+rssi_offset));
       Serial.write(FEND);
 
       // And then write the entire packet
@@ -170,7 +170,7 @@ void receiveCallback(int packet_size) {
     // recieved packet to the host.
     Serial.write(FEND);
     Serial.write(CMD_STAT_RSSI);
-    Serial.write((uint8_t)(last_rssi-rssi_offset));
+    Serial.write((uint8_t)(last_rssi+rssi_offset));
     Serial.write(FEND);
 
     // And then write the entire packet

From 68f403bf849933f1f22aa91d63dab78168565523 Mon Sep 17 00:00:00 2001
From: Matt Corallo <git@bluematt.me>
Date: Thu, 26 Sep 2019 18:50:04 -0400
Subject: [PATCH 2/2] Use Packet RSSI formula from datasheet section 5.5.5

---
 LoRa.cpp | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/LoRa.cpp b/LoRa.cpp
index eb3ec2a..64d5fec 100644
--- a/LoRa.cpp
+++ b/LoRa.cpp
@@ -219,6 +219,12 @@ uint8_t LoRaClass::packetRssiRaw() {
 
 int LoRaClass::packetRssi() {
   int pkt_rssi = (int)readRegister(REG_PKT_RSSI_VALUE);
+  int8_t pkt_snr = ((int8_t)readRegister(REG_PKT_SNR_VALUE));
+  if pkt_snr < 0 {
+    pkt_rssi = pkt_rssi * 16 / 15;
+  } else {
+    pkt_rssi += pkt_snr / 4;
+  }
   // TODO: change this to look at the actual model code
   if (_frequency < 820E6) pkt_rssi -= 7;
   pkt_rssi -= 157;