From 0d7bbac6a1820d092e5dd3ca2a474f327f15e115 Mon Sep 17 00:00:00 2001
From: heurist1 <git@heurist.co.uk>
Date: Sat, 30 Oct 2021 00:53:29 +0100
Subject: [PATCH] Added switching message length

Improves detections in test file from 77 to 80
---
 firmware/baseband/proc_adsbrx.cpp | 7 ++++++-
 firmware/baseband/proc_adsbrx.hpp | 1 +
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/firmware/baseband/proc_adsbrx.cpp b/firmware/baseband/proc_adsbrx.cpp
index 5a933bb1..7854accd 100644
--- a/firmware/baseband/proc_adsbrx.cpp
+++ b/firmware/baseband/proc_adsbrx.cpp
@@ -54,7 +54,7 @@ void ADSBRXProcessor::execute(const buffer_c8_t& buffer) {
 			
 			// 1 bit lasts 2 samples
 			if (sample_count & 1) {
-				if (bit_count >= 112)
+				if (bit_count >= msgLen)
 				{
 					const ADSBFrameMessage message(frame);
 					shared_memory.application_queue.push(message);
@@ -80,6 +80,10 @@ void ADSBRXProcessor::execute(const buffer_c8_t& buffer) {
 				if (!(bit_count & 7)) {
 					// Got one byte
 					frame.push_byte(byte);
+					// Check at the end of the first byte of the message
+					if ( (bit_count == 8) && !(byte & (0x10<<3)) ) { 
+						msgLen = 56; // DFs 16 or greater are long 112. DFs 15 or less are short 56.
+					}
 				}
 			} // Second sample of each bit
 			sample_count++;
@@ -126,6 +130,7 @@ void ADSBRXProcessor::execute(const buffer_c8_t& buffer) {
 					{
 						//if (c == ADSB_PREAMBLE_LENGTH) {
 						decoding = true;
+						msgLen = 112;
 						sample_count = 0;
 						bit_count = 0;
 						frame.clear();
diff --git a/firmware/baseband/proc_adsbrx.hpp b/firmware/baseband/proc_adsbrx.hpp
index f705b8c8..4d7ecf47 100644
--- a/firmware/baseband/proc_adsbrx.hpp
+++ b/firmware/baseband/proc_adsbrx.hpp
@@ -53,6 +53,7 @@ private:
 	float threshold { }, threshold_low { }, threshold_high { };
 	//size_t null_count{ 0 };
 	size_t bit_count { 0 }, sample_count { 0 };
+	size_t msgLen{ 112 };
 	//std::pair<float, uint8_t> shifter[ADSB_PREAMBLE_LENGTH];
 	float shifter[ADSB_PREAMBLE_LENGTH];
 	bool decoding { };