From 058ab29990944d4b224288107f92f0bc24a26ae9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?King=20K=C3=A9vin?= <kingkevin@cuvoodoo.info>
Date: Wed, 12 Oct 2022 17:34:27 +0200
Subject: [PATCH] main: first NEC decoding

---
 main.c | 29 ++++++++++++++++-------------
 1 file changed, 16 insertions(+), 13 deletions(-)

diff --git a/main.c b/main.c
index 37b0778..bdeaf4f 100644
--- a/main.c
+++ b/main.c
@@ -382,8 +382,8 @@ void time_isr(void) __interrupt(IRQ_TIM4)
 // IR capture timer counter
 void nec_uo_isr(void) __interrupt(IRQ_TIM1_UO)
 {
-	if (TIM1->SR1.fields.UIF) { // slot longer than NEC slot
-		nec_bit = -2; // set to invalid message
+	if (TIM1->SR1.fields.UIF) { // timer overflow
+		nec_bit = -2; // set to invalid message since it took longer than NEC slot
 		TIM1->SR1.fields.UIF = 0; // clear flag
 	}
 }
@@ -394,20 +394,12 @@ void nec_cc_isr(void) __interrupt(IRQ_TIM1_CC)
 	static uint32_t nec_bits = 0; // temporary buffer to construct message
 	if (TIM1->SR1.fields.CC1IF) { // start of burst
 		const uint16_t slot = (TIM1->CCR1H.reg << 8) + TIM1->CCR1L.reg;
-		nec_bit++; // start the bit
-		if (0 == nec_bit) { // AGC received
+		if (-1 == nec_bit) { // AGC received
 			nec_bits = 0; // reset message
 			if (slot < NEC_AGC_SLOT_MIN || slot > NEC_AGC_SLOT_MAX) {
 				nec_bit = -2; // slot invalid
 			}
-		} else if (32 == nec_bit) { // trailing pulse received
-			nec_msg[0] = (nec_bits >> 0); // save message
-			nec_msg[1] = (nec_bits >> 8); // save message
-			nec_msg[2] = (nec_bits >> 16); // save message
-			nec_msg[3] = (nec_bits >> 24); // save message
-			nec_flag = true; // notify we received a message
-			nec_bit = -2; // restart message
-		} else if (nec_bit > 0) {
+		} else if (nec_bit >= 0 && nec_bit < 32) {
 			if (slot >= NEC_0_SLOT_MIN && slot <= NEC_0_SLOT_MAX) {
 				// bit should already be 0
 			} else if (slot >= NEC_1_SLOT_MIN && slot <= NEC_1_SLOT_MAX) {
@@ -416,9 +408,20 @@ void nec_cc_isr(void) __interrupt(IRQ_TIM1_CC)
 				nec_bit = -2; // slot invalid
 			}
 		}
+		nec_bit++; // start the bit
 		TIM1->SR1.fields.CC1IF = 0; // clear flag
 	}
-	if (TIM1->SR1.fields.CC2IF) {
+	if (TIM1->SR1.fields.CC2IF) { // start of pause
+		if (32 == nec_bit) {
+			nec_msg[0] = (nec_bits >> 0); // save message
+			nec_msg[1] = (nec_bits >> 8); // save message
+			nec_msg[2] = (nec_bits >> 16); // save message
+			nec_msg[3] = (nec_bits >> 24); // save message
+			nec_flag = true; // notify we received a message
+			nec_bit = -2; // restart message
+		} else if (nec_bit >= 0) {
+			// here we could verify the burst length
+		}
 		TIM1->SR1.fields.CC2IF = 0; // clear flag
 	}
 }