From 2f894ab5a3f70d4ddeab03a8447ce88245ecf0d4 Mon Sep 17 00:00:00 2001
From: Piotr Wilkon <sq8vps@gmail.com>
Date: Thu, 31 Aug 2023 20:10:16 +0200
Subject: [PATCH] timer frq change, hamming distance using built-in fun

---
 Src/drivers/modem.c |  4 ++--
 Src/fx25.c          | 14 ++------------
 2 files changed, 4 insertions(+), 14 deletions(-)

diff --git a/Src/drivers/modem.c b/Src/drivers/modem.c
index 4c2388f..d0c8290 100644
--- a/Src/drivers/modem.c
+++ b/Src/drivers/modem.c
@@ -768,7 +768,7 @@ void ModemInit(void)
 	 TIM1->DIER |= TIM_DIER_UIE;
 
 	 //baudrate timer
-	 TIM3->PSC = 71; //72/72=1 MHz
+	 TIM3->PSC = 3; //72/9=18 MHz
 	 TIM3->DIER |= TIM_DIER_UIE;
 
 	 if(ModemConfig.modem > MODEM_9600)
@@ -927,7 +927,7 @@ void ModemInit(void)
 
 	markStep = 4000000 / (DAC_SINE_SIZE * markFreq) - 1;
 	spaceStep = 4000000 / (DAC_SINE_SIZE * spaceFreq) - 1;
-	baudRateStep = 1000000 / baudRate - 1;
+	baudRateStep = 18000000 / baudRate - 1;
 
 
 	TIM3->ARR = baudRateStep;
diff --git a/Src/fx25.c b/Src/fx25.c
index d01b16a..305df3e 100644
--- a/Src/fx25.c
+++ b/Src/fx25.c
@@ -25,23 +25,13 @@ const struct Fx25Mode Fx25ModeList[11] =
 	{.tag =  0x4A4ABEC4A724B796, .K = 64, .T = 64}
 };
 
-static uint8_t hammingDistance(uint64_t x, uint64_t y)
-{
-	x ^= y;
-	uint8_t distance = 0;
-	for(uint8_t i = 0; i < 64; i++)
-	{
-		distance += (x & 1);
-		x >>= 1;
-	}
-	return distance;
-}
+
 
 const struct Fx25Mode* Fx25GetModeForTag(uint64_t tag)
 {
 	for(uint8_t i = 0; i < sizeof(Fx25ModeList) / sizeof(*Fx25ModeList); i++)
 	{
-		if(hammingDistance(tag, Fx25ModeList[i].tag) <= FX25_MAX_DISTANCE)
+		if(__builtin_popcountll(tag ^ Fx25ModeList[i].tag) <= FX25_MAX_DISTANCE)
 			return &Fx25ModeList[i];
 	}
 	return NULL;