Allow deepsleep in rak4630 and make it restart well when power comes back (#7882)

* Make RAK4631 nodes power back on deep sleep

The devices will hang if the VBAT goes under 1.7V (Brown-out reset) and
they will never come back unless power supply goes completely off.

This kills unattended nodes.

Using the SystemOff the LPCOMP we can get the nodes back again when
power comes back, even if VBAT goes under 1.7V, which moreover is more
unlikely because the device is off.

* Adding support for heltec t114

And moved particularities to variant.h

* Remove old cpp comment that belongs to variant.h

It was a leftover.

* Trunk fix

---------

Co-authored-by: Tom Fifield <tom@tomfifield.net>

src/platform/nrf52/main-nrf52.cpp

@@ -14,6 +14,9 @@
 #include "error.h"
 #include "main.h"
 #include "meshUtils.h"
+#include "power.h"
+
+#include <hal/nrf_lpcomp.h>
 
 #ifdef BQ25703A_ADDR
 #include "BQ25713.h"
@@ -389,6 +392,23 @@ void cpuDeepSleep(uint32_t msecToWake)
         nrf_gpio_cfg_sense_set(BUTTON_PIN, sense);           // Apply SENSE to wake up the device from the deep sleep
 #endif
 
+#ifdef BATTERY_LPCOMP_INPUT
+        // Wake up if power rises again
+        nrf_lpcomp_config_t c;
+        c.reference = BATTERY_LPCOMP_THRESHOLD;
+        c.detection = NRF_LPCOMP_DETECT_UP;
+        c.hyst = NRF_LPCOMP_HYST_NOHYST;
+        nrf_lpcomp_configure(NRF_LPCOMP, &c);
+        nrf_lpcomp_input_select(NRF_LPCOMP, BATTERY_LPCOMP_INPUT);
+        nrf_lpcomp_enable(NRF_LPCOMP);
+
+        battery_adcEnable();
+
+        nrf_lpcomp_task_trigger(NRF_LPCOMP, NRF_LPCOMP_TASK_START);
+        while (!nrf_lpcomp_event_check(NRF_LPCOMP, NRF_LPCOMP_EVENT_READY))
+            ;
+#endif
+
         auto ok = sd_power_system_off();
         if (ok != NRF_SUCCESS) {
             LOG_ERROR("FIXME: Ignoring soft device (EasyDMA pending?) and forcing system-off!");
@@ -420,4 +440,4 @@ void enterDfuMode()
 #else
     enterUf2Dfu();
 #endif
-}
+}