added fixes for jeelabs#33 and jeelabs#34, also add new rf12_sendNow wrapper

Author: jcw

RF12.cpp

@@ -398,14 +398,11 @@ uint8_t rf12_recvDone () {
 /// rf12_recvDone() periodically, because it keeps the RFM12B logic going. If
 /// you don't, rf12_canSend() will never return true.
 uint8_t rf12_canSend () {
-    // no need to test with interrupts disabled: state TXRECV is only reached
-    // outside of ISR and we don't care if rxfill jumps from 0 to 1 here
+    // need interrupts off to avoid a race (and enable the RFM12B, thx Jorg!)
+    // see http://openenergymonitor.org/emon/node/1051?page=3
     if (rxstate == TXRECV && rxfill == 0 &&
-            (rf12_byte(0x00) & (RF_RSSI_BIT >> 8)) == 0) {
-        rf12_xfer(RF_IDLE_MODE); // stop receiver
-        //XXX just in case, don't know whether these RF12 reads are needed!
-        // rf12_xfer(0x0000); // status register
-        // rf12_xfer(RF_RX_FIFO_READ); // fifo read
+            (rf12_control(0x0000) & RF_RSSI_BIT) == 0) {
+        rf12_control(RF_IDLE_MODE); // stop receiver
         rxstate = TXIDLE;
         return 1;
     }
@@ -466,6 +463,20 @@ void rf12_sendStart (uint8_t hdr, const void* ptr, uint8_t len, uint8_t sync) {
     rf12_sendWait(sync);
 }
 
+/// @details
+/// Wait until transmission is possible, then start it as soon as possible.
+/// @note This uses a (brief) busy loop and will discard any incoming packets.
+/// @param hdr The header contains information about the destination of the
+///            packet to send, and flags such as whether this should be
+///            acknowledged - or if it actually is an acknowledgement.
+/// @param ptr Pointer to the data to send as packet.
+/// @param len Number of data bytes to send. Must be in the range 0 .. 65.
+void rf12_sendNow (uint8_t hdr, const void* ptr, uint8_t len) {
+  while (!rf12_canSend())
+    rf12_recvDone(); // keep the driver state machine going, ignore incoming
+  rf12_sendStart(hdr, ptr, len);
+}
+  
 /// @details
 /// Wait for completion of the preceding rf12_sendStart() call, using the
 /// specified low-power mode.

RF12.h

@@ -89,6 +89,8 @@ void rf12_sendStart(uint8_t hdr);
 void rf12_sendStart(uint8_t hdr, const void* ptr, uint8_t len);
 /// Deprecated: use rf12_sendStart(hdr,ptr,len) followed by rf12_sendWait(sync).
 void rf12_sendStart(uint8_t hdr, const void* ptr, uint8_t len, uint8_t sync);
+/// This variant loops on rf12_canSend() and then calls rf12_sendStart() asap.
+void rf12_sendNow(uint8_t hdr, const void* ptr, uint8_t len);
 
 /// Wait for send to finish.
 /// @param mode sleep mode 0=none, 1=idle, 2=standby, 3=powerdown.

intro.md

@@ -28,7 +28,7 @@ These are the main classes:
 * Sleepy - code to put an ATmega or ATtiny into very low-power mode
 
 The other major implementation in this library is the [RF12 wireless driver]
-(Md_intro_rf12.html) for the "RFM12" and RFM12B" wireless modules from HopeRF.
+(md_intro_rf12.html) for the "RFM12" and RFM12B" wireless modules from HopeRF.
 
 Last but not least, there are about a hundred demo sketches in the "examples"
 folder, ready to try out all sorts of features and tricks, and to easily hook

intro_rf12.md

@@ -16,7 +16,8 @@ this can be useful while wriitng and testing your own code with this driver.
 rf12_initialize(),
 rf12_recvDone(),
 rf12_canSend(),
-rf12_sendStart()
+rf12_sendStart(),
+rf12_sendNow()
 * Easy transmit wrappers:
 rf12_easyInit(),
 rf12_easyPoll(),