From 903bbac73d55f5fe3ec6f28e7fbebbfa7392e277 Mon Sep 17 00:00:00 2001
From: Klaus K Wilting <Klaus.K.Wilting@deutschebahn.com>
Date: Wed, 21 Mar 2018 22:32:59 +0100
Subject: [PATCH] DEVEUI handling improved (issue #5)

---
 src/loraconf.sample.h |  5 ++---
 src/lorawan.cpp       | 10 ++++++++++
 src/main.cpp          | 15 ++++++++++-----
 src/main.h            |  2 +-
 4 files changed, 23 insertions(+), 9 deletions(-)

diff --git a/src/loraconf.sample.h b/src/loraconf.sample.h
index 43f11c01..027e97f9 100644
--- a/src/loraconf.sample.h
+++ b/src/loraconf.sample.h
@@ -10,9 +10,8 @@
 /* 
 
 // Only define DEVEUI here if you don't want it to be derived from device's MAC address
-// Use little endian format (lsb)
-
-//static const u1_t DEVEUI[8]={ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
+// Use same format as in TTN console (cut & paste, for your convenience)
+static const u1_t DEVEUI[8]={ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
 
 // This EUI must be in little-endian format, so least-significant-byte
 // first. When copying an EUI from ttnctl output, this means to reverse
diff --git a/src/lorawan.cpp b/src/lorawan.cpp
index b47d6ea3..85164280 100644
--- a/src/lorawan.cpp
+++ b/src/lorawan.cpp
@@ -36,6 +36,16 @@ void gen_lora_deveui(uint8_t *pdeveui) {
                 }
 }
 
+// Function to do a byte swap in a byte array
+void RevBytes(unsigned char* b, size_t c)
+{
+  u1_t i;
+  for (i = 0; i < c / 2; i++)
+  { unsigned char t = b[i];
+    b[i] = b[c - 1 - i];
+    b[c - 1 - i] = t; }
+}
+
 #ifdef VERBOSE
 
 // Display a key
diff --git a/src/main.cpp b/src/main.cpp
index c1cf2128..5ac7daaf 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -75,6 +75,8 @@ void loadConfig(void);
 
 // defined in lorawan.cpp
 void gen_lora_deveui(uint8_t * pdeveui);
+void RevBytes(unsigned char* b, size_t c);
+
 #ifdef VERBOSE
     void printKeys(void);
 #endif // VERBOSE
@@ -82,11 +84,14 @@ void gen_lora_deveui(uint8_t * pdeveui);
 // LMIC callback functions
 void os_getArtEui (u1_t *buf) { memcpy(buf, APPEUI, 8);}
 void os_getDevKey (u1_t *buf) { memcpy(buf, APPKEY, 16);}
-#ifdef DEVEUI // if DEVEUI defined in loraconf.h use that and hardwire it in code ...
-    void os_getDevEui (u1_t *buf) { memcpy(buf, DEVEUI, 8);}
-#else // ... otherwise generate DEVEUI at runtime from devices's MAC
-    void os_getDevEui (u1_t *buf) { gen_lora_deveui(buf);} 
-#endif
+void os_getDevEui (u1_t* buf) {
+    #ifdef DEVEUI
+        memcpy(buf, DEVEUI, 8);
+        RevBytes(buf, 8); // TTN requires it in LSB First order, so we swap bytes
+    #else
+        gen_lora_deveui(buf);
+    #endif
+}
 
 // LMIC enhanced Pin mapping 
 const lmic_pinmap lmic_pins = {
diff --git a/src/main.h b/src/main.h
index 84392654..50191325 100644
--- a/src/main.h
+++ b/src/main.h
@@ -1,5 +1,5 @@
 // program version
-#define PROGVERSION                     "1.2.31" // use max 10 chars here!
+#define PROGVERSION                     "1.2.32" // use max 10 chars here!
 #define PROGNAME                        "PAXCNT"
 
 // Verbose enables serial output