X-Git-Url: https://oss.titaniummirror.com/gitweb/?a=blobdiff_plain;f=tos%2Fplatforms%2Ftelosb%2Fmac%2Ftkn154%2FTKN154TimingP.nc;h=fe2782b7ea753c53d1d9a915b8663d15c9be3edc;hb=e9bfab607e051bae6afb47b44892ce37541d1b44;hp=d9713c201d0985a60f553d5b45fa8ad8d96caa11;hpb=adf1de6c009d13b7b52e68535c63b28f59c97400;p=tinyos-2.x.git

diff --git a/tos/platforms/telosb/mac/tkn154/TKN154TimingP.nc b/tos/platforms/telosb/mac/tkn154/TKN154TimingP.nc
index d9713c20..fe2782b7 100644
--- a/tos/platforms/telosb/mac/tkn154/TKN154TimingP.nc
+++ b/tos/platforms/telosb/mac/tkn154/TKN154TimingP.nc
@@ -34,12 +34,10 @@
  */
 
 /** 
- * NOTE:
  * In slotted CSMA-CA frames must be sent on backoff boundaries (slot width:
- * 320 us). On TelosB the only clock source with sufficient accuracy is the
- * external quartz, unfortunately it is not precise enough (32.768 Hz).
- * Therefore, currently the following code is not even trying to achieve
- * accurate timing. 
+ * 320 us). The TelosB platform lacks a clock with sufficient precision and
+ * accuracy, i.e. for slotted CSMA-CA the timing is *not* standard compliant
+ * (this code is experimental)
  */
 
 #include "TKN154_platform.h"
@@ -49,24 +47,26 @@ module TKN154TimingP
   provides interface ReliableWait;
   provides interface ReferenceTime;
   uses interface TimeCalc;
-  uses interface LocalTime<T62500hz>;
+  uses interface GetNow<bool> as CCA;
+  uses interface Alarm<T62500hz,uint32_t> as SymbolAlarm;
+  uses interface Leds;
 }
 implementation
 {
+  enum {
+    S_WAIT_OFF,
+    S_WAIT_RX,
+    S_WAIT_TX,
+    S_WAIT_BACKOFF,
+  };
+  uint8_t m_state = S_WAIT_OFF;
 
-#define UWAIT1 nop();nop();nop();nop()
-#define UWAIT2 UWAIT1;UWAIT1
-#define UWAIT4 UWAIT2;UWAIT2
-#define UWAIT8 UWAIT4;UWAIT4
-
-  async command void CaptureTime.convert(uint16_t time, ieee154_reftime_t *localTime, int16_t offset)
+  async command error_t CaptureTime.convert(uint16_t time, ieee154_timestamp_t *localTime, int16_t offset)
   {
     // TimerB is used for capturing, it is sourced by ACLK (32768Hz),
-    // we now need to convert the capture "time" into ieee154_reftime_t.
+    // we now need to convert the capture "time" into ieee154_timestamp_t.
     // With the 32768Hz quartz we don't have enough precision anyway,
     // so the code below generates a timestamp that is not accurate
-    // (deviating about +-50 microseconds; this could probably
-    // improved if we don't go through LocalTime)
     uint16_t tbr1, tbr2, delta;
     uint32_t now;
     atomic {
@@ -74,51 +74,78 @@ implementation
         tbr1 = TBR;
         tbr2 = TBR;
       } while (tbr1 != tbr2); // majority vote required (see msp430 manual)
-      now = call LocalTime.get(); 
+      now = call SymbolAlarm.getNow(); 
     }
     if (time < tbr1)
       delta = tbr1 - time;
     else
       delta = ~(time - tbr1) + 1;
-    *localTime = now - delta*2 + offset;
+    *localTime = now - delta * 2 + offset; /* one tick of TimerB ~ two symbols */
+    return SUCCESS;
   }
 
-  async command void ReliableWait.busyWait(uint16_t dt)
+  async command bool ReliableWait.ccaOnBackoffBoundary(ieee154_timestamp_t *slot0)
   {
-    uint32_t start = call LocalTime.get();
-    while (!call TimeCalc.hasExpired(start, dt))
-      ;
+    // There is no point in trying
+    return (call CCA.getNow() ? 20: 0);
   }
 
-  async command void ReliableWait.waitCCA(ieee154_reftime_t *t0, uint16_t dt)
+  async command bool CaptureTime.isValidTimestamp(uint16_t risingSFDTime, uint16_t fallingSFDTime)
   {
-    while (!call TimeCalc.hasExpired(*t0, dt))
-      ;
-    signal ReliableWait.waitCCADone();
+    // smallest packet (ACK) takes 
+    // length field (1) + MPDU (5) = 6 byte => 12 * 16 us = 192 us 
+    return (fallingSFDTime - risingSFDTime) > 5;
   }
 
-  async command void ReliableWait.waitTx(ieee154_reftime_t *t0, uint16_t dt)
+  async command void ReliableWait.waitRx(uint32_t t0, uint32_t dt)
   {
-    while (!call TimeCalc.hasExpired(*t0, dt))
-      ;
-    signal ReliableWait.waitTxDone();
+    if (m_state != S_WAIT_OFF){
+      ASSERT(0);
+      return;
+    }
+    m_state = S_WAIT_RX;
+    call SymbolAlarm.startAt(t0 - 16, dt); // subtract 12 symbols required for Rx calibration
   }
 
-  async command void ReliableWait.waitRx(ieee154_reftime_t *t0, uint16_t dt)
+  async command void ReliableWait.waitTx(ieee154_timestamp_t *t0, uint32_t dt)
+  {
+    if (m_state != S_WAIT_OFF){
+      ASSERT(0);
+      return;
+    }
+    m_state = S_WAIT_TX;
+    call SymbolAlarm.startAt(*t0 - 16, dt); // subtract 12 symbols required for Tx calibration
+  }
+    
+  async command void ReliableWait.waitBackoff(uint32_t dt)
   {
-    while (!call TimeCalc.hasExpired(*t0, dt))
-      ;
-    signal ReliableWait.waitRxDone();
+    if (m_state != S_WAIT_OFF){
+      ASSERT(0);
+      return;
+    }
+    m_state = S_WAIT_BACKOFF;
+    call SymbolAlarm.start(dt);
   }
- 
-  async command void ReferenceTime.getNow(ieee154_reftime_t* reftime, uint16_t dt)
+
+  async event void SymbolAlarm.fired() 
+  {
+    switch (m_state)
+    {
+      case S_WAIT_RX: m_state = S_WAIT_OFF; signal ReliableWait.waitRxDone(); break;
+      case S_WAIT_TX: m_state = S_WAIT_OFF; signal ReliableWait.waitTxDone(); break;
+      case S_WAIT_BACKOFF: m_state = S_WAIT_OFF; signal ReliableWait.waitBackoffDone(); break;
+      default: ASSERT(0); break;
+    }
+  }
+
+  async command void ReferenceTime.getNow(ieee154_timestamp_t* timestamp, uint16_t dt)
   {
-    *reftime = call LocalTime.get();
+    *timestamp = call SymbolAlarm.getNow() + dt;
   }
 
-  async command uint32_t ReferenceTime.toLocalTime(ieee154_reftime_t* refTime)
+  async command uint32_t ReferenceTime.toLocalTime(const ieee154_timestamp_t* timestamp)
   {
-    return *refTime;
+    return *timestamp;
   } 
 
 }