X-Git-Url: https://www.fi.muni.cz/~kas/git//home/kas/public_html/git/?a=blobdiff_plain;ds=sidebyside;f=firmware%2Fmodbus.c;h=b726280f9922f9de4abea11a702e0a69ba58af0f;hb=d8f201d671212ce6ea71de49e852776e5f03f4e7;hp=00a9370a05bdaa872ce14b38f95de35d194d275b;hpb=6146a1caafd449cae4ce08134d763137424300c6;p=openparking.git

diff --git a/firmware/modbus.c b/firmware/modbus.c
index 00a9370..b726280 100644
--- a/firmware/modbus.c
+++ b/firmware/modbus.c
@@ -28,7 +28,7 @@ typedef uint8_t  bufptr_t;
 #endif
 
 static volatile bufptr_t buf_len, tx_ptr;
-static volatile uint8_t buffer[BUFSIZE], transmitting;;
+static volatile uint8_t buffer[BUFSIZE], transmitting;
 static volatile uint16_t last_rx;
 #ifndef mb_unit_id
 static uint8_t mb_unit_id;
@@ -169,18 +169,10 @@ uint8_t modbus_poll()
 		if (transmitting)
 			return 0;
 
-		if (buf_len == 0) // nothing received yet
-			return 0;
-
 		if (get_clock() - last_rx < REQ_TIMEOUT) // still receiving
 			return 0;
 
-		if (buf_len < 4) { // too short
-			buf_len = 0;
-			return 0;
-		}
-
-		if (buffer[0] != mb_unit_id) { // not for myself
+		if (buf_len < 4) { // too short (or not for us)
 			buf_len = 0;
 			return 0;
 		}
@@ -207,14 +199,14 @@ uint8_t modbus_poll()
 
 	switch (buffer[1]) { // function
 	case 3:
-		if (packet_len == 5)
+		if (packet_len == 6)
 			rv = read_holding_regs(
 				get_word(buffer, 2),
 				get_word(buffer, 4)
 			);
 		break;
 	case 6:
-		if (packet_len == 5)
+		if (packet_len == 6)
 			rv = write_single_reg(
 				get_word(buffer, 2),
 				get_word(buffer, 4)
@@ -241,16 +233,28 @@ uint8_t modbus_poll()
 ISR(USART_RX_vect)
 {
 	uint8_t rx_byte = UDR0;
+	clock_t now = get_clock();
+
+	if (transmitting) // how did we get here? discard it
+		goto out;
 
-	if (transmitting) // discard it
-		return;
+	if (buf_len && buffer[0] != mb_unit_id) // not for us
+		goto out;
 
-	buffer[buf_len] = rx_byte;
+	if (buf_len == BUFSIZE) { // overrun - discard the packet
+		buffer[0] = 0xFF;
+		buf_len = 1;
+		goto out;
+	}
 
-	if (buf_len + 1 < BUFSIZE) // ignore overruns
-		buf_len++;
+	if (now - last_rx >= REQ_TIMEOUT) { // new packet; start over
+		buf_len = 0;
+	}
 
-	last_rx = get_clock();
+	// TODO: we can probably calculate the CRC here as well
+	buffer[buf_len++] = rx_byte;
+out:
+	last_rx = now;
 }
 
 ISR(USART_TX_vect)
@@ -263,7 +267,8 @@ ISR(USART_TX_vect)
 
 ISR(USART_UDRE_vect)
 {
-	if (tx_ptr+1 >= buf_len) {
+	if (tx_ptr >= buf_len) {
+		UCSR0A |= _BV(TXC0); // clear the pending TXC flag
 		UCSR0B |= _BV(TXCIE0); // enable xmit complete irq
 		UCSR0B &= ~_BV(UDRIE0); // disable ourselves
 	} else {