From fbb66f9cd5fe15637d11f16c0eb4f6dbcb5b5213 Mon Sep 17 00:00:00 2001
From: Atis Elsts <atis.elsts@gmail.com>
Date: Mon, 6 Jun 2016 23:12:09 +0300
Subject: [PATCH] TSCH: allow to configure channel scanning duration during the
 join phase

---
 core/net/mac/tsch/tsch-conf.h |  7 +++++++
 core/net/mac/tsch/tsch.c      | 13 +++++++------
 2 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/core/net/mac/tsch/tsch-conf.h b/core/net/mac/tsch/tsch-conf.h
index 631f47d03..d8d58f0ff 100644
--- a/core/net/mac/tsch/tsch-conf.h
+++ b/core/net/mac/tsch/tsch-conf.h
@@ -191,4 +191,11 @@
 #define TSCH_RADIO_ON_DURING_TIMESLOT 0
 #endif
 
+/* How long to scan each channel in the scanning phase */
+#ifdef TSCH_CONF_CHANNEL_SCAN_DURATION
+#define TSCH_CHANNEL_SCAN_DURATION TSCH_CONF_CHANNEL_SCAN_DURATION
+#else
+#define TSCH_CHANNEL_SCAN_DURATION CLOCK_SECOND
+#endif
+
 #endif /* __TSCH_CONF_H__ */
diff --git a/core/net/mac/tsch/tsch.c b/core/net/mac/tsch/tsch.c
index de6619dc5..292744ecc 100644
--- a/core/net/mac/tsch/tsch.c
+++ b/core/net/mac/tsch/tsch.c
@@ -609,24 +609,25 @@ PT_THREAD(tsch_scan(struct pt *pt))
 
   static struct input_packet input_eb;
   static struct etimer scan_timer;
+  /* Time when we started scanning on current_channel */
+  static clock_time_t current_channel_since;
 
   ASN_INIT(current_asn, 0, 0);
 
   etimer_set(&scan_timer, CLOCK_SECOND / TSCH_ASSOCIATION_POLL_FREQUENCY);
+  current_channel_since = clock_time();
 
   while(!tsch_is_associated && !tsch_is_coordinator) {
     /* Hop to any channel offset */
-    static int current_channel = 0;
-    /* Time when we started scanning on current_channel */
-    static clock_time_t current_channel_since = 0;
+    static uint8_t current_channel = 0;
 
     /* We are not coordinator, try to associate */
     rtimer_clock_t t0;
     int is_packet_pending = 0;
-    clock_time_t now_seconds = clock_seconds();
+    clock_time_t now_time = clock_time();
 
     /* Switch to a (new) channel for scanning */
-    if(current_channel == 0 || now_seconds != current_channel_since) {
+    if(current_channel == 0 || now_time - current_channel_since > TSCH_CHANNEL_SCAN_DURATION) {
       /* Pick a channel at random in TSCH_JOIN_HOPPING_SEQUENCE */
       uint8_t scan_channel = TSCH_JOIN_HOPPING_SEQUENCE[
           random_rand() % sizeof(TSCH_JOIN_HOPPING_SEQUENCE)];
@@ -635,7 +636,7 @@ PT_THREAD(tsch_scan(struct pt *pt))
         current_channel = scan_channel;
         PRINTF("TSCH: scanning on channel %u\n", scan_channel);
       }
-      current_channel_since = now_seconds;
+      current_channel_since = now_time;
     }
 
     /* Turn radio on and wait for EB */