From: Jan "Yenya" Kasprzak <kas@fi.muni.cz>
Date: Fri, 22 May 2015 22:13:07 +0000 (+0200)
Subject: Use TX end IRQ instead of busy wait
X-Git-Url: https://www.fi.muni.cz/~kas/git//home/kas/public_html/git/?p=openparking.git;a=commitdiff_plain;h=db62b021ea5b82e91eaacb345ad81439a4cb41dc

Use TX end IRQ instead of busy wait
---

diff --git a/firmware/modbus.c b/firmware/modbus.c
index 0c238c2..2b2a255 100644
--- a/firmware/modbus.c
+++ b/firmware/modbus.c
@@ -43,7 +43,6 @@ static uint8_t mb_unit_id;
 
 #define UART_BAUD	9600
 #define UBRR_VAL        ((F_CPU + 8UL * UART_BAUD) / (16UL*UART_BAUD) - 1)
-#define wait_one_byte()	_delay_us(10*1000000/UART_BAUD)
 
 /*
  * According to Wikipedia, it is indeed 28 bits = 3.5 bytes without
@@ -267,14 +266,19 @@ ISR(USART_RX_vect)
 	}
 }
 
+ISR(USART_TX_vect)
+{
+	UCSR0B &= ~_BV(TXCIE0); // disable further IRQs
+	ctl_pin_off();
+}
+
 ISR(USART_UDRE_vect)
 {
 	ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
 		if (tx_head == tx_tail) {
+			UCSR0B |= _BV(TXCIE0); // enable xmit complete irq
 			UCSR0B &= ~_BV(UDRIE0);
 			tx_tail = tx_head = 0;
-			wait_one_byte(); // FIXME: too long busy-wait
-			ctl_pin_off();
 		} else {
 			UDR0 = txbuf[tx_tail];
 			tx_tail = bufptr_inc(tx_tail);
diff --git a/firmware/rs485.c b/firmware/rs485.c
index 6d16a2a..7aec92c 100644
--- a/firmware/rs485.c
+++ b/firmware/rs485.c
@@ -34,7 +34,6 @@ static volatile char rxbuf[BUFSIZE], txbuf[BUFSIZE];
 
 #define UART_BAUD	9600
 #define UBRR_VAL        ((F_CPU + 8UL * UART_BAUD) / (16UL*UART_BAUD) - 1)
-#define wait_one_byte()	_delay_us(10*1000000/UART_BAUD)
 
 void rs485_init()
 {
@@ -99,13 +98,18 @@ ISR(USART_RX_vect)
 	sei();
 }
 
+ISR(USART_TX_vect)
+{
+	UCSR0B &= ~_BV(TXCIE0); // disable further IRQs
+	ctl_pin_off();
+}
+
 ISR(USART_UDRE_vect)
 {
 	cli();
 	if (tx_head == tx_tail) {
+		UCSR0B |= _BV(TXCIE0); // enable xmit complete irq
 		UCSR0B &= ~_BV(UDRIE0);
-		wait_one_byte();
-		ctl_pin_off();
 	} else {
 		UDR0 = txbuf[tx_tail];
 		tx_tail = bufptr_inc(tx_tail);