Allow disabling I/Q inversion on RX

matthijskooijman · matthijskooijman · commit db786f367f2d · 2016-02-20T12:24:04.000+01:00
By uncommenting a maco in config.h, this inversion is enabled, and
communication between nodes can be enabled. This should be used just for
debugging, though.
diff --git a/examples/raw/raw.ino b/examples/raw/raw.ino
@@ -20,6 +20,11 @@
 #include <hal/hal.h>
 #include <SPI.h>
 
+#if !defined(DISABLE_INVERT_IQ_ON_RX)
+#error This example requires DISABLE_INVERT_IQ_ON_RX to be set. Update \
+       config.h in the lmic library to set it.
+#endif
+
 lmic_pinmap pins = {
   .nss = SS,
   .rxtx = 8, // Not connected
diff --git a/src/lmic/config.h b/src/lmic/config.h
@@ -39,4 +39,14 @@
 //#define DISABLE_MCMD_PING_SET // set ping freq, automatically disabled by DISABLE_PING
 //#define DISABLE_MCMD_BCNI_ANS // next beacon start, automatical disabled by DISABLE_BEACON
 
+// In LoRaWAN, a gateway applies I/Q inversion on TX, and nodes do the
+// same on RX. This ensures that gateways can talk to nodes and vice
+// versa, but gateways will not hear other gateways and nodes will not
+// hear other nodes. By uncommenting this macro, this inversion is
+// disabled and this node can hear other nodes. If two nodes both have
+// this macro set, they can talk to each other (but they can no longer
+// hear gateways). This should probably only be used when debugging
+// and/or when talking to the radio directly (e.g. like in the "raw"
+// example).
+#define DISABLE_INVERT_IQ_ON_RX
 #endif // _lmic_config_h_
diff --git a/src/lmic/radio.c b/src/lmic/radio.c
@@ -547,8 +547,10 @@ static void rxlora (u1_t rxmode) {
     writeReg(RegLna, LNA_RX_GAIN);
     // set max payload size
     writeReg(LORARegPayloadMaxLength, 64);
+#if !defined(DISABLE_INVERT_IQ_ON_RX)
     // use inverted I/Q signal (prevent mote-to-mote communication)
     writeReg(LORARegInvertIQ, readReg(LORARegInvertIQ)|(1<<6));
+#endif
     // set symbol timeout (for single rx)
     writeReg(LORARegSymbTimeoutLsb, LMIC.rxsyms);
     // set sync word
