From 21992cfc5410263750b481044ea77c431adff8d0 Mon Sep 17 00:00:00 2001
From: Vineet K <git@vineetk.net>
Date: Sun, 21 Apr 2024 17:22:43 -0400
Subject: [PATCH] read and play notes from serial

---
 notes.c | 46 ++++++++++++++++++++++++++++++++--------------
 1 file changed, 32 insertions(+), 14 deletions(-)

diff --git a/notes.c b/notes.c
index 3f93cc5..7902efe 100644
--- a/notes.c
+++ b/notes.c
@@ -38,12 +38,12 @@ unsigned short freqs[] = {
 	FREQ(1750),
 	FREQ(2000),
 
-	[255] = 0	// used as a 'silent' note
+	[32] = 0	// used as a 'silent' note
 };
 unsigned char note = 0;
 // 0 = buttons write note+cycles+\xff to UART
 // 1 = buttons don't do anything, speaker reads note+cycles+\xff from UART
-unsigned char mode = 0;
+unsigned char mode = '0';
 
 ISR (PCINT0_vect)
 {
@@ -82,7 +82,7 @@ void
 usart_init(void)
 {
 	// 115200 bps, RX/TX enabled
-	UBRR0 = 8;
+	UBRR0 = 103;
 	UCSR0B = (1 << RXEN0) | (1 << TXEN0);
 	UCSR0C = (1 << UCSZ01) | (1 << UCSZ00);
 }
@@ -94,6 +94,13 @@ usart_send(unsigned char c)
 	UDR0 = c;
 }
 
+void
+usart_send_str(const char *c)
+{
+	for (unsigned char i = 0; c[i] != '\0'; i++)
+		usart_send(c[i]);
+}
+
 unsigned char
 usart_read(void)
 {
@@ -125,9 +132,14 @@ main(void)
 	// Sends Square wave to the Speaker When a Button is Pressed
 	unsigned short cycles = 0;
 	unsigned char tmp = 0;
-	for (;;) {
+	for (unsigned char n = 0;; n = (n + 1) % 2) {
+		if (UCSR0A & (1 << RXC0)) {
+			mode = UDR0;
+			PORTD &= ~(1 << P_SPKR);
+			usart_send(mode);
+		}
 		// check if any buttons are pressed, otherwise don't play a note
-		if (((PINB & PCMSK0) | (PINC & PCMSK1) | (PIND & PCMSK2)) == 0) {
+		if (mode != '1' && ((PINB & PCMSK0) | (PINC & PCMSK1) | (PIND & PCMSK2)) == 0) {
 			// if a button was released, then send note and cycles played
 			if (cycles > 0) {
 				usart_send(tmp);
@@ -135,16 +147,11 @@ main(void)
 				usart_send(LOW(cycles));
 				usart_send(0xff);
 				cycles = 0;
-			} else {
-				if (UCSR0A & (1 << RXC0)) {
-					mode = UDR0;
-					usart_send(mode);
-				}
 			}
 			continue;
 		}
 
-		if (mode == 0) {
+		if (mode == '0') {
 			// Prepare Timer/Counter
 			TCNT1 = 1;
 			tmp = note;
@@ -159,15 +166,26 @@ main(void)
 			TIFR1 |= 1 << OCF1A;
 			TCCR1B &= ~(1 << CS11);
 			cycles = (cycles + 1) % 0xffff;
-		} else if (mode == 0xb0) {
+		} else if (mode == '1') {
 			note = usart_read();
+			if (note >= '0') note -= '0';
 			tmp = usart_read();
 			cycles = tmp << 8;
 			tmp = usart_read();
 			cycles |= tmp;
-			(void)usart_read();
+			tmp = usart_read();
+
+			// reset to default mode when an invalid note is read
+			if (tmp != 'z' || note > '@') {
+				mode = '0';
+				continue;
+			}
+
+			for (unsigned short i = 0; i < cycles; i++) {
+				usart_send(HIGH(cycles));
+				usart_send(LOW(cycles));
+				usart_send(0);
 
-			for (unsigned char i = 0; i < cycles; i++) {
 				TCNT1 = 1;
 				OCR1A = freqs[note];
 				TCCR1B |= 1 << CS11;