Add feature to have no DIO connection

README.md

@@ -137,6 +137,20 @@ library what pin you used through the pin mapping (see below).
 [SPI]: https://www.arduino.cc/en/Reference/SPI
 
 ### DIO pins
+
+Since now, a software feature has been added to remove needing DIO connections. 
+Of course, you can continue to use DIO mapping has follow, but in case you're 
+restricted in GPIO available, you can avoid using any GPIO connection ;-)
+to activate this feature, you just need to declare 3 .dio to LMIC_UNUSED_PIN,
+in your sketch as detailled in Pin mapping section. 
+
+If you want to use hardware IRQ but not having 3 IO pins, another trick is
+to OR DIO0/DOI1/DIO2 into one. This is possible because the stack check 
+all IRQs, even if only one is triggered. Doing this is quite easy, just add 3
+1N4148 diodes to each output and a pulldown resistor, see schematic example
+on [WeMos Lora shield](https://github.com/hallard/WeMos-Lora).
+
+If you still have DIO connection, following is explaining how they work.
 The DIO (digitial I/O) pins on the transceiver board can be configured
 for various functions. The LMIC library uses them to get instant status
 information from the transceiver. For example, when a LoRa transmission
@@ -219,13 +233,41 @@ The names refer to the pins on the transceiver side, the numbers refer
 to the Arduino pin numbers (to use the analog pins, use constants like
 `A0`). For the DIO pins, the three numbers refer to DIO0, DIO1 and DIO2
 respectively. Any pins that are not needed should be specified as
-`LMIC_UNUSED_PIN`. The nss and dio0 pin is required, the others can
-potentially left out (depending on the environments and requirements,
-see the notes above for when a pin can or cannot be left out).
+`LMIC_UNUSED_PIN`. The nss is required the others can potentially left out
+(depending on the environments and requirements, see the notes above for when
+a pin can or cannot be left out).
 
 The name of this struct must always be `lmic_pins`, which is a special name
 recognized by the library.
 
+If you don't have any DIO pins connected to GPIO (new software feature)
+you just need to declare 3 .dio to LMIC_UNUSED_PIN, in your sketch 
+That's all, stack will do the job for you.
+
+#### [WeMos Lora Shield](https://github.com/hallard/WeMos-Lora)
+```arduino
+// Example with NO DIO pin connected
+const lmic_pinmap lmic_pins = {
+    .nss = 16,
+    .rxtx = LMIC_UNUSED_PIN,
+    .rst = LMIC_UNUSED_PIN,
+    .dio = {LMIC_UNUSED_PIN, LMIC_UNUSED_PIN, LMIC_UNUSED_PIN},
+};
+```
+
+If you used 3 diodes OR hardware trick like in this [schematic](https://github.com/hallard/WeMos-Lora),
+just indicate which GPIO is used on DIO0 definition as follow:
+
+```arduino
+// Example with 3 DIO OR'ed on one pin connected to GPIO14
+const lmic_pinmap lmic_pins = {
+    .nss = 16,
+    .rxtx = LMIC_UNUSED_PIN,
+    .rst = LMIC_UNUSED_PIN,
+    .dio = {15, LMIC_UNUSED_PIN, LMIC_UNUSED_PIN},
+};
+```
+
 #### LoRa Nexus by Ideetron
 This board uses the following pin mapping:
 

src/hal/hal.cpp

@@ -16,24 +16,31 @@
 
 // -----------------------------------------------------------------------------
 // I/O
+// default we do not use IRQ line and DIO output
+static bool check_dio = 0;
 
 static void hal_io_init () {
-    // NSS and DIO0 are required, DIO1 is required for LoRa, DIO2 for FSK
+    // NSS is required
     ASSERT(lmic_pins.nss != LMIC_UNUSED_PIN);
-    ASSERT(lmic_pins.dio[0] != LMIC_UNUSED_PIN);
-    ASSERT(lmic_pins.dio[1] != LMIC_UNUSED_PIN || lmic_pins.dio[2] != LMIC_UNUSED_PIN);
+
+    // No more needed, if dio pins are declared as unused, then LIMC will check
+    // interrputs directly into Lora module register, avoiding needed GPIO line to IRQ
+    //ASSERT(lmic_pins.dio[0] != LMIC_UNUSED_PIN);
+    //ASSERT(lmic_pins.dio[1] != LMIC_UNUSED_PIN || lmic_pins.dio[2] != LMIC_UNUSED_PIN);
 
     pinMode(lmic_pins.nss, OUTPUT);
     if (lmic_pins.rxtx != LMIC_UNUSED_PIN)
         pinMode(lmic_pins.rxtx, OUTPUT);
     if (lmic_pins.rst != LMIC_UNUSED_PIN)
         pinMode(lmic_pins.rst, OUTPUT);
 
-    pinMode(lmic_pins.dio[0], INPUT);
-    if (lmic_pins.dio[1] != LMIC_UNUSED_PIN)
-        pinMode(lmic_pins.dio[1], INPUT);
-    if (lmic_pins.dio[2] != LMIC_UNUSED_PIN)
-        pinMode(lmic_pins.dio[2], INPUT);
+    // if using DIO lines, DIO0 is always required, DIO1 is required for LoRa, DIO2 for FSK
+    for (uint8_t i = 0; i < NUM_DIO; ++i) {
+        if (lmic_pins.dio[i] != LMIC_UNUSED_PIN) {
+            check_dio = 1; // we need to use DIO line check
+            pinMode(lmic_pins.dio[i], INPUT);
+        }
+    }
 }
 
 // val == 1  => tx 1
@@ -58,19 +65,23 @@ void hal_pin_rst (u1_t val) {
 static bool dio_states[NUM_DIO] = {0};
 
 static void hal_io_check() {
-    uint8_t i;
-    for (i = 0; i < NUM_DIO; ++i) {
-        if (lmic_pins.dio[i] == LMIC_UNUSED_PIN)
-            continue;
-
-        if (dio_states[i] != digitalRead(lmic_pins.dio[i])) {
-            dio_states[i] = !dio_states[i];
-            if (dio_states[i])
-                radio_irq_handler(i);
+    // We have DIO line connected?
+    if (check_dio == 1) {
+        uint8_t i;
+        for (i = 0; i < NUM_DIO; ++i) {
+            if (dio_states[i] != digitalRead(lmic_pins.dio[i])) {
+                dio_states[i] = !dio_states[i];
+                if (dio_states[i]) {
+                    radio_irq_handler(i);
+                }
+            }
         }
+    } else {
+        // Check IRQ flags in radio module
+        if ( radio_has_irq() ) 
+            radio_irq_handler(0);
     }
 }
-
 // -----------------------------------------------------------------------------
 // SPI
 

src/lmic/oslmic.h

@@ -81,6 +81,7 @@ u1_t radio_rand1 (void);
 #define DECLARE_LMIC extern struct lmic_t LMIC
 
 void radio_init (void);
+u1_t radio_has_irq (void);
 void radio_irq_handler (u1_t dio);
 void os_init (void);
 void os_runloop (void);

src/lmic/radio.c

@@ -669,7 +669,10 @@ static void startrx (u1_t rxmode) {
 
 // get random seed from wideband noise rssi
 void radio_init () {
+
+#ifndef ESP8266
     hal_disableIRQs();
+#endif
 
     // manually reset radio
 #ifdef CFG_sx1276_radio
@@ -725,7 +728,9 @@ void radio_init () {
 
     opmode(OPMODE_SLEEP);
 
+#ifndef ESP8266
     hal_enableIRQs();
+#endif
 }
 
 // return next random byte derived from seed buffer
@@ -759,6 +764,28 @@ static CONST_TABLE(u2_t, LORA_RXDONE_FIXUP)[] = {
     [SF12] = us2osticks(31189), // (1022 ticks)
 };
 
+
+// called by hal to check if we got one IRQ
+// This trick directly read the Lora module IRQ register
+// and thus avoid any IRQ line used to controler
+u1_t radio_has_irq (void) {
+    u1_t flags ;
+    if( (readReg(RegOpMode) & OPMODE_LORA) != 0) { // LORA modem
+        flags = readReg(LORARegIrqFlags);
+        if( flags & ( IRQ_LORA_TXDONE_MASK | IRQ_LORA_RXDONE_MASK | IRQ_LORA_RXTOUT_MASK ) ) 
+            return 1;
+    } else { // FSK modem
+        flags = readReg(FSKRegIrqFlags2);
+        if ( flags & ( IRQ_FSK2_PACKETSENT_MASK | IRQ_FSK2_PAYLOADREADY_MASK) ) 
+            return 1;
+        flags = readReg(FSKRegIrqFlags1);
+        if ( flags & IRQ_FSK1_TIMEOUT_MASK ) 
+            return 1;
+    }
+
+    return 0;
+}
+
 // called by hal ext IRQ handler
 // (radio goes to stanby mode after tx/rx operations)
 void radio_irq_handler (u1_t dio) {