From: Mikko Rasa <tdb@tdb.fi>
Date: Mon, 28 Oct 2013 20:20:28 +0000 (+0200)
Subject: Send at least four S88 data octets per packets if possible
X-Git-Url: http://git.tdb.fi/?p=model-railway-devices.git;a=commitdiff_plain;h=dfe51654709d752ac19ecfcca5d6d1f1e605ce52

Send at least four S88 data octets per packets if possible

Each packet has three bytes of overhead, which is pretty significant if
only a single data byte is sent.  Grouping them in larger units increases
throughput and only produces a negligible increase in latency.
---

diff --git a/arducontrol/s88.c b/arducontrol/s88.c
index 1ce5740..bce0a2a 100644
--- a/arducontrol/s88.c
+++ b/arducontrol/s88.c
@@ -28,14 +28,18 @@ void s88_init(void)
 
 void s88_check(void)
 {
-	// Only send one packet per check to avoid blocking
-	if(ringbuffer_fill(s88_buffer)>0)
+	uint8_t count = ringbuffer_fill(s88_buffer);
+	if(count>=4 || (count>0 && !s88_read_count))
 	{
-		uint8_t reply[3];
+		uint8_t reply[10];
+		uint8_t i;
+
 		reply[0] = S88_DATA;
-		reply[1] = s88_out_index++;
-		reply[2] = ringbuffer_pop(s88_buffer);
-		interface_send(reply, sizeof(reply));
+		reply[1] = s88_out_index;
+		for(i=0; i<count; ++i)
+			reply[2+i] = ringbuffer_pop(s88_buffer);
+		interface_send(reply, 2+count);
+		s88_out_index += count;
 	}
 }