From e813e6bf462b8cb6a2f910745f0890bed71e9407 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?King=20K=C3=A9vin?= <kingkevin@cuvoodoo.info>
Date: Wed, 12 Oct 2022 17:37:00 +0200
Subject: [PATCH] main: add NEC code transmission

---
 main.c | 93 +++++++++++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 76 insertions(+), 17 deletions(-)

diff --git a/main.c b/main.c
index cb01af4..783edd8 100644
--- a/main.c
+++ b/main.c
@@ -174,6 +174,82 @@ static void timer_ir_in(void)
 	IRM_ON_PORT->ODR.reg |= IRM_ON_PIN; // switch IR demodulator on
 }
 
+#define TIM1_PERIOD 421U // 16E6/(0+1)/38000
+
+// configure timer to transmit IR burst at 38 kHz
+static void timer_ir_out(void)
+{
+	IRM_ON_PORT->ODR.reg &= ~IRM_ON_PIN; // switch IR demodulator off
+
+	TIM1->CR1.reg = 0; // disable counter before reconfiguring it
+	TIM1->CCER1.reg = 0; // reset register
+	TIM1->CCER2.reg = 0; // reset register
+	TIM1->IER.reg = 0; // reset interrupts
+	TIM1->PSCRH.reg = 0; // set prescaler to get most precise 38 kHz
+	TIM1->PSCRL.reg = 0; // 16E6/(0+1)/65536 = down to 244 Hz
+	TIM1->ARRH.reg = (TIM1_PERIOD >> 8); // set auto-reload register for 38 kHz period
+	TIM1->ARRL.reg = (TIM1_PERIOD & 0xff); // 16E6/(0+1)/38000
+	TIM1->CCR4H.reg = (TIM1_PERIOD / 3) >> 8; // set duty cycle to 33%
+	TIM1->CCR4L.reg = (TIM1_PERIOD / 3 ) & 0xff; // set duty cycle to 33%
+	TIM1->CCMR4.output_fields.OC4M = 6; // set PWM1 mode
+	TIM1->CCMR4.output_fields.CC4S = 0; // use channel as output
+	TIM1->CCER2.fields.CC4E = 1; // enable channel output
+	TIM1->BKR.fields.MOE = 1; // enable outputs
+	TIM1->SR1.reg = 0; // clear all flags
+	TIM1->CNTRL.reg = 0; // reset counter
+	TIM1->CNTRH.reg = 0; // reset counter
+	TIM1->CR1.fields.OPM = 1; // send one pulse at a time
+	TIM1->EGR.fields.UG = 1; // transfer all registers
+	// don't enable timer yet
+}
+
+// transmit IR pulses
+static void nec_pulse(uint16_t pulses, bool mark)
+{
+	if (mark) {
+		TIM1->CCR4H.reg = (TIM1_PERIOD / 3) >> 8; // set duty cycle to 33%
+		TIM1->CCR4L.reg = (TIM1_PERIOD / 3 ) & 0xff; // set duty cycle to 33%
+	} else {
+		TIM1->CCR4H.reg = 0; // set duty cycle to 0%
+		TIM1->CCR4L.reg = 0; // set duty cycle to 0%
+	}
+	while (pulses--) {
+		TIM1->CR1.fields.CEN = 1; // enable counter to start PWM for 1 pulse
+		while (TIM1->CR1.fields.CEN); // wait until pulse completes
+	}
+	// ensure we are off at the end
+	TIM1->CCR4H.reg = 0; // set duty cycle to 0%
+	TIM1->CCR4L.reg = 0; // set duty cycle to 0%
+}
+
+// transmit 4 byte NEC code over IR (LSb first)
+static void nec_transmit(uint32_t code)
+{
+	if (NULL == code) {
+		return;
+	}
+
+	timer_ir_out(); // configure to transmit pulses
+	sim(); // disable interrupts to keep timings tight
+	// all time are hand tuned
+	nec_pulse(333, true); // send AGC burst, 9 ms
+	nec_pulse(166, false); // AGC space, 4.5 ms
+	// transmit bits
+	for (uint8_t i = 0; i < 32; i++) {
+		nec_pulse(21, true); // bit burst, 560 us
+		if (code & 0x1) {
+			nec_pulse(61, false); // bit space, 2.25 ms - 560 us
+		} else {
+			nec_pulse(21, false); // bit space, 1.12 ms - 560 us
+		}
+		code >>= 1; // go to next bit
+	}
+	nec_pulse(22, true); // end pulse, 560 us
+	rim(); // re-enable interrupts
+
+	timer_ir_in(); // go back to IR capture
+}
+
 void main(void)
 {
 	sim(); // disable interrupts (while we reconfigure them)
@@ -265,23 +341,6 @@ void main(void)
 	TIM4->CR1.fields.URS = 1; // only update on overflow
 	TIM4->CR1.fields.CEN = 1; // enable counter
 
-/*
-	// configure timer to modulate IR LEDs at 38 kHz
-	TIM1->PSCRH.reg = 0; // set prescaler to get most precise 38 kHz
-	TIM1->PSCRL.reg = 0; // 16E6/(0+1)/65536 = down to 244 Hz
-	#define TIM1_PERIOD 421U // 16E6/(0+1)/38000
-	TIM1->ARRH.reg = (TIM1_PERIOD >> 8); // set auto-reload register for 38 kHz period
-	TIM1->ARRL.reg = (TIM1_PERIOD & 0xff); // 16E6/(0+1)/38000
-	TIM1->CCR4H.reg = (TIM1_PERIOD / 3) >> 8; // set duty cycle to 33%
-	TIM1->CCR4L.reg = (TIM1_PERIOD / 3 ) & 0xff; // set duty cycle to 33%
-	TIM1->CCMR4.output_fields.OC4M = 6; // set PWM1 mode
-	TIM1->CCMR4.output_fields.CC4S = 0; // use channel as output
-	TIM1->CCER2.fields.CC4E = 1; // enable channel output
-	TIM1->BKR.fields.MOE = 1; // enable outputs
-	TIM1->EGR.fields.UG = 1; // transfer all registers
-	TIM1->CR1.fields.CEN = 1; // enable counter to start PWM
-*/
-
 	// configure timer to receive IR message
 	timer_ir_in();