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NRF52 Repeater Powersaving #1238

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NRF52 Repeater Powersaving #1238

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20fbf7a
variants: RAK4631: Enable RF module reset pin
fschrempf Dec 16, 2025
25c2415
simple_repeater: Use constexpr variables for powersaving timings
fschrempf Jan 2, 2026
fbcb16a
simple_repeater: Extend active interval on serial CLI activity
fschrempf Jan 2, 2026
9a659fa
Support sleep for NRF52 boards by suspending the main task
fschrempf Jan 2, 2026
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16 changes: 11 additions & 5 deletions examples/simple_repeater/main.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -20,8 +20,12 @@ void halt() {
static char command[160];

// For power saving
constexpr unsigned long ACTIVE_TIME_SEC_INUSE = 2 * 60; // 2 minutes
constexpr unsigned long ACTIVE_TIME_SEC_IDLE = 5; // 5 seconds
constexpr unsigned long IDLE_PERIOD_SEC = 30 * 60; // 30 minutes

unsigned long lastActive = 0; // mark last active time
unsigned long nextSleepinSecs = 120; // next sleep in seconds. The first sleep (if enabled) is after 2 minutes from boot
unsigned long nextSleepinSecs = ACTIVE_TIME_SEC_INUSE; // next sleep in seconds

void setup() {
Serial.begin(115200);
Expand Down Expand Up @@ -110,6 +114,8 @@ void loop() {
Serial.print('\n');
command[len - 1] = 0; // replace newline with C string null terminator
char reply[160];
lastActive = millis();
nextSleepinSecs = ACTIVE_TIME_SEC_INUSE;
the_mesh.handleCommand(0, command, reply); // NOTE: there is no sender_timestamp via serial!
if (reply[0]) {
Serial.print(" -> "); Serial.println(reply);
Expand All @@ -125,14 +131,14 @@ void loop() {
#endif
rtc_clock.tick();

if (the_mesh.getNodePrefs()->powersaving_enabled && // To check if power saving is enabled
if (the_mesh.getNodePrefs()->powersaving_enabled &&
the_mesh.millisHasNowPassed(lastActive + nextSleepinSecs * 1000)) { // To check if it is time to sleep
if (!the_mesh.hasPendingWork()) { // No pending work. Safe to sleep
board.sleep(1800); // To sleep. Wake up after 30 minutes or when receiving a LoRa packet
board.sleep(IDLE_PERIOD_SEC); // To sleep. Wake up after 30 minutes or when receiving a LoRa packet
lastActive = millis();
nextSleepinSecs = 5; // Default: To work for 5s and sleep again
nextSleepinSecs = ACTIVE_TIME_SEC_IDLE; // Default: To work for 5s and sleep again
} else {
nextSleepinSecs += 5; // When there is pending work, to work another 5s
nextSleepinSecs += ACTIVE_TIME_SEC_IDLE; // When there is pending work, to work another 5s
}
}
}
11 changes: 11 additions & 0 deletions src/helpers/NRF52Board.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@
#include <bluefruit.h>

static BLEDfu bledfu;
static SoftwareTimer sleep_timer;

static void connect_callback(uint16_t conn_handle) {
(void)conn_handle;
Expand All @@ -17,10 +18,20 @@ static void disconnect_callback(uint16_t conn_handle, uint8_t reason) {
MESH_DEBUG_PRINTLN("BLE client disconnected");
}

static void sleep_timer_callback(TimerHandle_t xTimerID) {
resumeLoop();
}

void NRF52Board::begin() {
startup_reason = BD_STARTUP_NORMAL;
}

void NRF52Board::sleep(uint32_t secs) {
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@4np 4np Jan 5, 2026 •
edited
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Psuedo code (I am not sure about the PIN numbers):

// NRF52Board.cpp (file scope)

static SoftwareTimer sleep_timer;
static bool sleep_timer_inited = false;
static volatile bool sleeping = false;

static void sleep_timer_callback(TimerHandle_t) {
  sleeping = false;
  resumeLoop();
}

void NRF52Board::sleep(uint32_t secs) {
  if (secs == 0) return;

  // Convert seconds->ms with overflow clamp
  uint64_t ms64 = (uint64_t)secs * 1000ULL;
  uint32_t ms = (ms64 > 0xFFFFFFFFULL) ? 0xFFFFFFFFUL : (uint32_t)ms64;

  // Helper: detect SX1262 DIO1 asserted (pending/latched IRQ).
  auto dio1_high = []() -> bool {
#if defined(PIN_LORA_DIO1)
    return digitalRead(PIN_LORA_DIO1) == HIGH;
#elif defined(LORA_DIO1)
    return digitalRead(LORA_DIO1) == HIGH;
#else
    return false; // if unknown, we can't gate (better than breaking build)
#endif
  };

  // SX1262/RAK4630: if DIO1 is HIGH (IRQ latched), do NOT suspendLoop() or you can deadlock.
  if (dio1_high()) return;

  sleeping = true;

  // Cancel any previous schedule to avoid stale wake callbacks.
  sleep_timer.stop();

  // Initialize + (re)configure timer
  if (!sleep_timer_inited) {
    sleep_timer_inited = true;
  }
  sleep_timer.begin(ms, sleep_timer_callback, nullptr, /*repeating=*/false);
  sleep_timer.start();

  // Optional extra safety: re-check after arming timer to avoid a tiny race window
  // where an IRQ asserts DIO1 between the first check and suspendLoop().
  if (dio1_high()) {
    sleeping = false;
    sleep_timer.stop();   // don't leave a stray timer armed
    return;
  }

  suspendLoop();
}

void NRF52Board::wakeFromInterrupt() {
  // Optional micro-optimization: if we're not sleeping, no need to stop the timer.
  // But still safe to call resumeLoop() unconditionally.
  if (sleeping) {
    sleeping = false;
    sleep_timer.stop();   // prevent later spurious callback
  }
  resumeLoop();
}

So this should likely fix the unresponsive repeater issue:

  // SX1262/RAK4630: if DIO1 is HIGH (IRQ latched), do NOT suspendLoop() or you can deadlock.
  if (dio1_high()) return;

sleep_timer.begin(secs * 1000, sleep_timer_callback, NULL, false);
sleep_timer.start();
suspendLoop();
}

void NRF52BoardDCDC::begin() {
NRF52Board::begin();

Expand Down
1 change: 1 addition & 0 deletions src/helpers/NRF52Board.h
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,7 @@ class NRF52Board : public mesh::MainBoard {
virtual uint8_t getStartupReason() const override { return startup_reason; }
virtual float getMCUTemperature() override;
virtual void reboot() override { NVIC_SystemReset(); }
virtual void sleep(uint32_t secs);
};

/*
Expand Down
5 changes: 5 additions & 0 deletions src/helpers/radiolib/RadioLibWrappers.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,11 @@ static
void setFlag(void) {
// we sent a packet, set the flag
state |= STATE_INT_READY;

#ifdef NRF52_PLATFORM
// NRF52 uses suspendLoop() for powersaving, resume on RX interrupt here
if (state & STATE_RX) resumeLoop();
#endif
}

void RadioLibWrapper::begin() {
Expand Down
2 changes: 1 addition & 1 deletion variants/rak4631/RAK4631Board.h
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Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,7 @@
// LoRa radio module pins for RAK4631
#define P_LORA_DIO_1 47
#define P_LORA_NSS 42
#define P_LORA_RESET RADIOLIB_NC // 38
#define P_LORA_RESET 38
#define P_LORA_BUSY 46
#define P_LORA_SCLK 43
#define P_LORA_MISO 45
Expand Down