X-Git-Url: https://www.fi.muni.cz/~kas/git//home/kas/public_html/git/?a=blobdiff_plain;f=firmware%2Fmodbus.c;h=c895c5f30ec71336e08a4820b059b9cfec22f827;hb=087a60aae1ad8d3f96f94601c68910154f884735;hp=4e8456354e1a5385d630eb7f4cd59cff0f6606a3;hpb=885b506cd11fefff2d2653385c9a2725e8167b79;p=openparking.git

diff --git a/firmware/modbus.c b/firmware/modbus.c
index 4e84563..c895c5f 100644
--- a/firmware/modbus.c
+++ b/firmware/modbus.c
@@ -14,7 +14,7 @@
 #include "clock.h"
 #include "modbus.h"
 
-#define BUFSIZE 128 // maximum request size
+#define BUFSIZE 180 // maximum request size
 
 // configure the control pin
 #define ctl_pin_setup()	do { DDRD  |=  _BV(PD2); } while (0)
@@ -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;
@@ -159,7 +159,7 @@ static mb_exception write_single_reg(uint16_t reg, uint16_t val)
 	return MB_OK;
 }
 
-void modbus_poll()
+uint8_t modbus_poll()
 {
 	bufptr_t packet_len;
 	uint16_t crc;
@@ -167,22 +167,14 @@ void modbus_poll()
 
 	ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
 		if (transmitting)
-			return;
-
-		if (buf_len == 0) // nothing received yet
-			return;
+			return 0;
 
 		if (get_clock() - last_rx < REQ_TIMEOUT) // still receiving
-			return;
-
-		if (buf_len < 4) { // too short
-			buf_len = 0;
-			return;
-		}
+			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;
+			return 0;
 		}
 
 		transmitting = 1; // disable further reads
@@ -197,7 +189,7 @@ void modbus_poll()
 			transmitting = 0;
 			buf_len = 0;
 		}
-		return;
+		return 1;
 	}
 
 	packet_len -= 2; // strip the CRC
@@ -207,14 +199,14 @@ void 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)
@@ -234,21 +226,35 @@ void modbus_poll()
 	tx_ptr = 0;
 	ctl_pin_on();
 	UCSR0B |= _BV(UDRIE0);
+
+	return 1;
 }
 
 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)
@@ -261,7 +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 {