Optionally disable downlinks to save power (Caution: renders device non-compliant)

README.md

@@ -1,3 +1,16 @@
+**This fork was specifically created for those developpers wanting to build real low-power applications. Unlike the mainstream version and other forks, this version allows us to disable downlinks completely. Calling LMIC_setDownlinks(false) turns downlinks off anytime dynamically, reducing active times down to the minimum necessary to transmit uplink messages. As an example, typical uplink+downlink intervals at SF7 vary around 6-9 seconds. With downlinks deactivated, uplinks only take ~50 msec to complete.**
+
+# Important note
+
+This version of Arduino-lmic does not comply with LoRaWAN™ Specification v1.1 since downlinks should never be disabled.
+
+From LoRaWAN™ Specification v1.1:
+
+> 3.3.6 Important notice on receive windows
+> An end-device SHALL NOT transmit another uplink message before it either has received a
+> downlink message in the first or second receive window of the previous transmission, or the
+> second receive window of the previous transmission is expired.
+
 # Arduino-LMIC library
 
 This repository contains the IBM LMIC (LoRaWAN-MAC-in-C) library, slightly

project_config/lmic_project_config.h

@@ -1,6 +1,6 @@
 // project-specific definitions
-//#define CFG_eu868 1
-#define CFG_us915 1
+#define CFG_eu868 1
+//#define CFG_us915 1
 //#define CFG_au915 1
 //#define CFG_as923 1
 // #define LMIC_COUNTRY_CODE LMIC_COUNTRY_CODE_JP	/* for as923-JP */

src/lmic/config.h

@@ -109,10 +109,10 @@
 // define this in lmic_project_config.h to disable all code related to joining
 //#define DISABLE_JOIN
 // define this in lmic_project_config.h to disable all code related to ping
-//#define DISABLE_PING
+#define DISABLE_PING
 // define this in lmic_project_config.h to disable all code related to beacon tracking.
 // Requires ping to be disabled too
-//#define DISABLE_BEACONS
+#define DISABLE_BEACONS
 
 // define these in lmic_project_config.h to disable the corresponding MAC commands.
 // Class A

src/lmic/lmic.c

@@ -1818,8 +1818,8 @@ static void setupRx2DnData (xref2osjob_t osjob) {
 static void processRx1DnData (xref2osjob_t osjob) {
     LMIC_API_PARAMETER(osjob);
 
-    if( LMIC.dataLen == 0 || !processDnData() )
-        schedRx12(sec2osticks(LMIC.rxDelay +(int)DELAY_EXTDNW2), FUNC_ADDR(setupRx2DnData), LMIC.dn2Dr);
+    if( LMIC.dataLen == 0 || !processDnData() )       
+      schedRx12(sec2osticks(LMIC.rxDelay +(int)DELAY_EXTDNW2), FUNC_ADDR(setupRx2DnData), LMIC.dn2Dr);
 }
 
 
@@ -1833,7 +1833,13 @@ static void setupRx1DnData (xref2osjob_t osjob) {
 static void updataDone (xref2osjob_t osjob) {
     LMIC_API_PARAMETER(osjob);
 
-    txDone(sec2osticks(LMIC.rxDelay), FUNC_ADDR(setupRx1DnData));
+    if (LMIC.downlinkEnabled == 0)
+    {
+      LMIC.opmode &= ~(OP_TXDATA|OP_TXRXPEND);
+      reportEventAndUpdate(EV_TXCOMPLETE);
+    }
+    else
+      txDone(sec2osticks(LMIC.rxDelay), FUNC_ADDR(setupRx1DnData));
 }
 
 // ========================================
@@ -2817,6 +2823,8 @@ void LMIC_reset (void) {
     LMIC.netDeviceTime = 0;     // the "invalid" time.
     LMIC.netDeviceTimeFrac = 0;
 #endif // LMIC_ENABLE_DeviceTimeReq
+
+    LMIC.downlinkEnabled = 1;
 }
 
 

src/lmic/lmic.h

@@ -643,6 +643,8 @@ struct lmic_t {
 
     u1_t        noRXIQinversion;
     u1_t        saveIrqFlags;   // last LoRa IRQ flags
+
+    u1_t        downlinkEnabled;
 };
 
 //! \var struct lmic_t LMIC
@@ -723,6 +725,12 @@ lmic_compliance_rx_action_t LMIC_complianceRxMessage(u1_t port, const u1_t *pMes
 DECL_ON_LMIC_EVENT;
 #endif /* LMIC_ENABLE_onEvent */
 
+// Disable downlinks
+inline void LMIC_setDownlinks(bit_t enabled)
+{
+  LMIC.downlinkEnabled = enabled;
+}
+
 // Special APIs - for development or testing
 // !!!See implementation for caveats!!!