simple_repeater: Allow to idle the CPU for powersaving

Use the idle.interval parameter to stall the loop to save power. The
loop is halted for the given amount of seconds before continuing the
processing. Only receiving packets will cause an interruption of the
idling.

Unfortunately it's not easily possible to interrupt the idling on user
input such as CLI activity or user button inputs as those things are
currently not interrupt-driven. Therefore the UI and the CLI will
remain unresponsive during sleep. After booting the CLI will be
available for three minutes before the first sleep interval and if
a CLI command is issued this period will be extended for another three
minutes.

On a RAK4631 repeater this can reduce the power consumption during RX
mode from around 12 mA to around 7.5 mA.

Signed-off-by: Frieder Schrempf <[email protected]>

Author: fschrempf

examples/simple_repeater/main.cpp

@@ -19,6 +19,12 @@ void halt() {
 
 static char command[160];
 
+constexpr unsigned long ACTIVE_TIME_MS_INUSE = 3 * 60 * 1000; // 3 minutes
+constexpr unsigned long ACTIVE_TIME_MS_IDLE = 5 * 1000;       // 5 seconds
+
+unsigned long active_timestamp;
+unsigned long active_time_ms = ACTIVE_TIME_MS_INUSE;
+
 void setup() {
   Serial.begin(115200);
   delay(1000);
@@ -82,6 +88,7 @@ void setup() {
 
   // send out initial Advertisement to the mesh
   the_mesh.sendSelfAdvertisement(16000);
+  active_timestamp = millis();
 }
 
 void loop() {
@@ -103,6 +110,8 @@ void loop() {
     Serial.print('\n');
     command[len - 1] = 0;  // replace newline with C string null terminator
     char reply[160];
+    active_timestamp = millis();
+    active_time_ms = ACTIVE_TIME_MS_INUSE;
     the_mesh.handleCommand(0, command, reply);  // NOTE: there is no sender_timestamp via serial!
     if (reply[0]) {
       Serial.print("  -> "); Serial.println(reply);
@@ -117,4 +126,11 @@ void loop() {
   ui_task.loop();
 #endif
   rtc_clock.tick();
+
+  if (the_mesh.getIdleInterval() && ((millis() - active_timestamp) > active_time_ms) &&
+      !the_mesh.hasOutboundPackets()) {
+    radio_driver.blockTaskUntilRXEvent(the_mesh.getIdleInterval() * 1000);
+    active_timestamp = millis();
+    active_time_ms = ACTIVE_TIME_MS_IDLE;
+  }
 }