From 3c311f1b2729f43a356b02542a7001db623395e1 Mon Sep 17 00:00:00 2001
From: mmaroti <mmaroti>
Date: Fri, 12 Feb 2010 21:52:45 +0000
Subject: [PATCH] Fix the time stamping correction code Committed on the Free
 edition of March Hare Software CVSNT Server. Upgrade to CVS Suite for more
 features and support: http://march-hare.com/cvsnt/

---
 tos/chips/rf2xx/rf230/RF230DriverHwAckP.nc | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/tos/chips/rf2xx/rf230/RF230DriverHwAckP.nc b/tos/chips/rf2xx/rf230/RF230DriverHwAckP.nc
index 2bd762d3..790e79ed 100644
--- a/tos/chips/rf2xx/rf230/RF230DriverHwAckP.nc
+++ b/tos/chips/rf2xx/rf230/RF230DriverHwAckP.nc
@@ -186,8 +186,11 @@ implementation
 		PLL_CALIBRATION_TIME = (uint16_t)(180 * RADIO_ALARM_MICROSEC),
 		CCA_REQUEST_TIME = (uint16_t)(140 * RADIO_ALARM_MICROSEC),
 
-		TX_SFD_DELAY = (uint16_t)((128 + 5*32 + 16) * RADIO_ALARM_MICROSEC),
-		RX_SFD_DELAY = (uint16_t)((16 + 32) * RADIO_ALARM_MICROSEC),
+		// 8 undocumented delay, 128 for CSMA, 16 for delay, 5*32 for preamble and SFD
+		TX_SFD_DELAY = (uint16_t)((8 + 128 + 16 + 5*32) * RADIO_ALARM_MICROSEC),
+		
+		// 32 for frame length, 16 for delay
+		RX_SFD_DELAY = (uint16_t)((32 + 16) * RADIO_ALARM_MICROSEC),
 	};
 
 	tasklet_async event void RadioAlarm.fired()
@@ -689,7 +692,18 @@ tasklet_async command uint8_t RadioState.getChannel()
 		if( crcValid && call PacketTimeStamp.isValid(rxMsg) )
 		{
 			uint32_t time32 = call PacketTimeStamp.timestamp(rxMsg);
-			time32 -= RX_SFD_DELAY + (length << (RADIO_ALARM_MILLI_EXP - 5));
+			length = getHeader(rxMsg)->length;
+
+/*
+ * If you hate floating point arithmetics and do not care of up to 400 microsecond time stamping errors,
+ * then define RF230_HWACK_SLOPPY_TIMESTAMP, which will be significantly faster.
+ */
+#ifdef RF230_HWACK_SLOPPY_TIMESTAMP
+			time32 -= (uint16_t)(RX_SFD_DELAY) + ((uint16_t)(length) << (RADIO_ALARM_MILLI_EXP - 5));
+#else
+			time32 -= (uint16_t)(RX_SFD_DELAY) + (uint16_t)(32.0 * RADIO_ALARM_MICROSEC * (uint16_t)length);
+#endif
+
 			call PacketTimeStamp.set(rxMsg, time32);
 		}
 
-- 
2.39.2