From: Jan "Yenya" Kasprzak <kas@fi.muni.cz>
Date: Sat, 23 May 2015 15:48:50 +0000 (+0200)
Subject: modbus: make modbus_poll return value
X-Git-Url: https://www.fi.muni.cz/~kas/git//home/kas/public_html/git/?p=openparking.git;a=commitdiff_plain;h=6146a1caafd449cae4ce08134d763137424300c6

modbus: make modbus_poll return value

- the return value is usable for determining whether a potentially
lengthy packet processing went on.
---

diff --git a/firmware/modbus.c b/firmware/modbus.c
index 4e84563..00a9370 100644
--- a/firmware/modbus.c
+++ b/firmware/modbus.c
@@ -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 +167,22 @@ void modbus_poll()
 
 	ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
 		if (transmitting)
-			return;
+			return 0;
 
 		if (buf_len == 0) // nothing received yet
-			return;
+			return 0;
 
 		if (get_clock() - last_rx < REQ_TIMEOUT) // still receiving
-			return;
+			return 0;
 
 		if (buf_len < 4) { // too short
 			buf_len = 0;
-			return;
+			return 0;
 		}
 
 		if (buffer[0] != mb_unit_id) { // not for myself
 			buf_len = 0;
-			return;
+			return 0;
 		}
 
 		transmitting = 1; // disable further reads
@@ -197,7 +197,7 @@ void modbus_poll()
 			transmitting = 0;
 			buf_len = 0;
 		}
-		return;
+		return 1;
 	}
 
 	packet_len -= 2; // strip the CRC
@@ -234,6 +234,8 @@ void modbus_poll()
 	tx_ptr = 0;
 	ctl_pin_on();
 	UCSR0B |= _BV(UDRIE0);
+
+	return 1;
 }
 
 ISR(USART_RX_vect)
diff --git a/firmware/modbus.h b/firmware/modbus.h
index 9f5afa6..e762b70 100644
--- a/firmware/modbus.h
+++ b/firmware/modbus.h
@@ -8,8 +8,17 @@
  * All bugs by Jan "Yenya" Kasprzak <kas@fi.muni.cz> :-)
  */
 
+/*
+ * Call this at the beginning of the program.
+ */
 void modbus_init(uint8_t unit_id);
-void modbus_poll();
+
+/*
+ * Call this frequently. Returns 0 when no data was received
+ * and the processing went on quickly. Returns 1 after potentially lengthy
+ * packet processing.
+ */
+uint8_t modbus_poll();
 
 typedef enum {
 	MB_OK = 0,