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/Power.cpp

@@ -194,7 +194,7 @@ static HasBatteryLevel *batteryLevel; // Default to NULL for no battery level se
 
 #ifdef BATTERY_PIN
 
-static void adcEnable()
+void battery_adcEnable()
 {
 #ifdef ADC_CTRL // enable adc voltage divider when we need to read
 #ifdef ADC_USE_PULLUP
@@ -214,7 +214,7 @@ static void adcEnable()
 #endif
 }
 
-static void adcDisable()
+static void battery_adcDisable()
 {
 #ifdef ADC_CTRL // disable adc voltage divider when we need to read
 #ifdef ADC_USE_PULLUP
@@ -320,7 +320,7 @@ class AnalogBatteryLevel : public HasBatteryLevel
             uint32_t raw = 0;
             float scaled = 0;
 
-            adcEnable();
+            battery_adcEnable();
 #ifdef ARCH_ESP32 // ADC block for espressif platforms
             raw = espAdcRead();
             scaled = esp_adc_cal_raw_to_voltage(raw, adc_characs);
@@ -332,7 +332,7 @@ class AnalogBatteryLevel : public HasBatteryLevel
             raw = raw / BATTERY_SENSE_SAMPLES;
             scaled = operativeAdcMultiplier * ((1000 * AREF_VOLTAGE) / pow(2, BATTERY_SENSE_RESOLUTION_BITS)) * raw;
 #endif
-            adcDisable();
+            battery_adcDisable();
 
             if (!initial_read_done) {
                 // Flush the smoothing filter with an ADC reading, if the reading is plausibly correct
@@ -906,13 +906,8 @@ void Power::readPowerStatus()
             low_voltage_counter++;
             LOG_DEBUG("Low voltage counter: %d/10", low_voltage_counter);
             if (low_voltage_counter > 10) {
-#ifdef ARCH_NRF52
-                // We can't trigger deep sleep on NRF52, it's freezing the board
-                LOG_DEBUG("Low voltage detected, but not trigger deep sleep");
-#else
                 LOG_INFO("Low voltage detected, trigger deep sleep");
                 powerFSM.trigger(EVENT_LOW_BATTERY);
-#endif
             }
         } else {
             low_voltage_counter = 0;

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!");

src/power.h

@@ -144,4 +144,6 @@ class Power : private concurrency::OSThread
 #endif
 };
 
+void battery_adcEnable();
+
 extern Power *power;

variants/nrf52840/heltec_mesh_node_t114/variant.h

@@ -210,6 +210,16 @@ No longer populated on PCB
 #define VBAT_AR_INTERNAL AR_INTERNAL_3_0
 #define ADC_MULTIPLIER (4.916F)
 
+// rf52840 AIN2 = Pin 4
+#define BATTERY_LPCOMP_INPUT NRF_LPCOMP_INPUT_2
+
+// We have AIN2 with a VBAT divider so AIN2 = VBAT * (100/490)
+// We have the device going deep sleep under 3.1V, which is AIN2 = 0.63V
+// So we can wake up when VBAT>=VDD is restored to 3.3V, where AIN2 = 0.67V
+// Ratio 0.67/3.3 = 0.20, so we can pick a bit higher, 2/8 VDD, which means
+// VBAT=4.04V
+#define BATTERY_LPCOMP_THRESHOLD NRF_LPCOMP_REF_SUPPLY_2_8
+
 #define HAS_RTC 0
 #ifdef __cplusplus
 }

variants/nrf52840/rak4631/variant.h

@@ -267,6 +267,20 @@ SO GPIO 39/TXEN MAY NOT BE DEFINED FOR SUCCESSFUL OPERATION OF THE SX1262 - TG
 #define VBAT_AR_INTERNAL AR_INTERNAL_3_0
 #define ADC_MULTIPLIER 1.73
 
+// RAK4630 AIN0 = nrf52840 AIN3 = Pin 5
+#define BATTERY_LPCOMP_INPUT NRF_LPCOMP_INPUT_3
+
+// We have AIN3 with a VBAT divider so AIN3 = VBAT * (1.5/2.5)
+// We have the device going deep sleep under 3.1V, which is AIN3 = 1.86V
+// So we can wake up when VBAT>=VDD is restored to 3.3V, where AIN3 = 1.98V
+// 1.98/3.3 = 6/10, but that's close to the VBAT divider, so we
+// pick 6/8VDD, which means VBAT=4.1V.
+// Reference:
+// VDD=3.3V AIN3=5/8*VDD=2.06V VBAT=1.66*AIN3=3.41V
+// VDD=3.3V AIN3=11/16*VDD=2.26V VBAT=1.66*AIN3=3.76V
+// VDD=3.3V AIN3=6/8*VDD=2.47V VBAT=1.66*AIN3=4.1V
+#define BATTERY_LPCOMP_THRESHOLD NRF_LPCOMP_REF_SUPPLY_11_16
+
 #define HAS_RTC 1
 
 #define HAS_ETHERNET 1