Here's the sketch:

// SUMMARY: This demo sketch runs on the AM612 PIR v607 PCBto transmit battery voltage (heartbeat) and motion detections to a MySensors gateway using MySensors protocols.

// Note: because this is a passive node, node ID must be set manually to a unique sensor node ID:
#define MY_NODE_ID 70  // Passive mode requires static node ID

//#define MY_CORE_ONLY

//#define MY_PASSIVE_NODE

#define MY_RADIO_NRF5_ESB



/**
 * The MySensors Arduino library handles the wireless radio link and protocol
 * between your home built sensors/actuators and HA controller of choice.
 * The sensors forms a self healing radio network with optional repeaters. Each
 * repeater and gateway builds a routing tables in EEPROM which keeps track of the
 * network topology allowing messages to be routed to nodes.
 *
 * Created by Henrik Ekblad <henrik.ekblad@mysensors.org>
 * Copyright (C) 2013-2017 Sensnology AB
 * Full contributor list: https://github.com/mysensors/Arduino/graphs/contributors
 *
 * Documentation: http://www.mysensors.org
 * Support Forum: http://forum.mysensors.org
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * version 2 as published by the Free Software Foundation.
 *
 *******************************
 *
 * REVISION HISTORY
 * Version 1.0 - tekka
 *
 * DESCRIPTION
 * Passive node example: This is a passive & independent reporting node
 *
 */

// This demo sketch also draws from the MySensor's example MotionSensor sketch.


//#define IS_NRF51  //true iff the target is an nRF51.  If an nRF52, then comment this line out!


#define PIR_DETECTION_PIN 2 
#define SHORT_WAIT 100
//#define MY_RF24_CHANNEL 125
#define MY_NRF5_ESB_CHANNEL 125
//#define MY_NRF5_ESB_PA_LEVEL NRF5_PA_MAX
//#define MY_TRANSPORT_WAIT_READY_MS  3000
//#define MY_TRANSPORT_MAX_TSM_FAILURES 2
//#define MY_SLEEP_TRANSPORT_RECONNECT_TIMEOUT_MS 3000
//#define MY_TRANSPORT_UPLINK_CHECK_DISABLED
//#define MY_PARENT_NODE_IS_STATIC
//#define MY_PARENT_NODE_ID 0
#define MY_DEBUG_VERBOSE_NRF5_ESB
//#define MY_NRF5_ESB_REVERSE_ACK_RX
//#define MY_NRF5_ESB_REVERSE_ACK_TX
#define MY_DEBUG
#define MY_DEBUG_VERBOSE_TRANSPORT

#include <MySensors.h>


// Enable debug prints



volatile bool motion_change=false;

void blinkityBlink(uint8_t pulses, uint8_t repetitions) {
  for (int x=0;x<repetitions;x++) {
    for (int i=0;i<pulses;i++) {
      digitalWrite(LED_BUILTIN,HIGH);
      wait(20);
      digitalWrite(LED_BUILTIN,LOW);
      wait(100);
    }    
      wait(500);
  }
}

void disableNfc() {  //only applied to nRF52

#ifndef IS_NRF51
  //Make pins 9 and 10 usable as GPIO pins.
  NRF_NFCT->TASKS_DISABLE=1;  //disable NFC
  NRF_NVMC->CONFIG=1;  // Write enable the UICR
  NRF_UICR->NFCPINS=0; //Make pins 9 and 10 usable as GPIO pins.
  NRF_NVMC->CONFIG=0;  // Put the UICR back into read-only mode.
#endif
}


void turnOffRadio() {
  NRF_RADIO->TASKS_DISABLE=1;
  while (!(NRF_RADIO->EVENTS_DISABLED)) {}  //until radio is confirmed disabled
}

void turnOffUarte0() {
#ifndef IS_NRF51  
  NRF_UARTE0->TASKS_STOPRX = 1;
  NRF_UARTE0->TASKS_STOPTX = 1;
//  NRF_UARTE0->TASKS_SUSPEND = 1;
  NRF_UARTE0->ENABLE=0;  //disable UART0
  while (NRF_UARTE0->ENABLE!=0) {};  //wait until UART0 is confirmed disabled.
#endif

#ifdef IS_NRF51
  NRF_UART0->TASKS_STOPRX = 1;
  NRF_UART0->TASKS_STOPTX = 1;
  NRF_UART0->TASKS_SUSPEND = 1;
  NRF_UART0->ENABLE=0;  //disable UART0
  while (NRF_UART0->ENABLE!=0) {};  //wait until UART0 is confirmed disabled.
#endif
}

void turnOffAdc() {
#ifndef IS_NRF51
  if (NRF_SAADC->ENABLE) { //if enabled, then disable the SAADC
    NRF_SAADC->TASKS_STOP=1;
    while (NRF_SAADC->EVENTS_STOPPED) {} //wait until stopping of SAADC is confirmed
    NRF_SAADC->ENABLE=0;  //disable the SAADC
    while (NRF_SAADC->ENABLE) {} //wait until the disable is confirmed
  }
#endif
}


void turnOffHighFrequencyClock() {
    NRF_CLOCK->TASKS_HFCLKSTOP = 1;
    while ((NRF_CLOCK->HFCLKSTAT) & 0x0100) {}  //wait as long as HF clock is still running.
}


void mySleepPrepare() {  //turn-off energy drains prior to sleep
  turnOffHighFrequencyClock();
  turnOffRadio();
  //turnOffUarte0();
}
 

void activateLpComp() {
  NRF_LPCOMP->PSEL=0; // monitor AIN0 (i.e. pin P0.02 on nRF52832 PIR Motion Sensor v607).
  while (!(NRF_LPCOMP->PSEL==0)) {} //wait until confirmed
  NRF_LPCOMP->REFSEL=3;  // choose 1/2 VDD as the reference voltage
  while (!(NRF_LPCOMP->REFSEL==3)) {} //wait until confirmed
  NRF_LPCOMP->ANADETECT=0;  //detect CROSS events on PIR detection pin
  while (NRF_LPCOMP->ANADETECT!=0) {} //wait until confirmed
  NRF_LPCOMP->INTENSET=B1000;  //Enable interrupt for CROSS event
  while (!(((NRF_LPCOMP->INTENSET)&B1000)==B1000)) {} //wait until confirmed
  NRF_LPCOMP->ENABLE=1;  //Enable LPCOMP
  while (!(NRF_LPCOMP->ENABLE==1)) {} //wait until confirmed
  NRF_LPCOMP->TASKS_START=1;  //start the LPCOMP
  while (!(NRF_LPCOMP->EVENTS_READY)) {}  //wait until ready
  
  NVIC_SetPriority(LPCOMP_IRQn, 15);
  NVIC_ClearPendingIRQ(LPCOMP_IRQn);
  NVIC_EnableIRQ(LPCOMP_IRQn);
}

void suspendLpComp() { //suspend getting more interrupts from LPCOMP before the first interrupt can be handled
  if ((NRF_LPCOMP->ENABLE) && (NRF_LPCOMP->EVENTS_READY)) {  //if LPCOMP is enabled
    NRF_LPCOMP->INTENCLR=B0100;  //disable interrupt from LPCOMP
    while (((NRF_LPCOMP->INTENCLR)&B0100)==B0100) {} //wait until confirmed
  }
}

void resumeLpComp() { //suspend getting interrupts from LPCOMP
  NRF_LPCOMP->INTENSET=B0100;  //Enable interrupt for UP event
  while (((NRF_LPCOMP->INTENSET)&B1000)!=B0100) {} //wait until confirmed
}


#define CHILD_ID 1   // Id of the motion sensor child
#define ID_S_MULTIMETER        28

// Initialize motion message

MyMessage msg(CHILD_ID, V_TRIPPED);
MyMessage msg_S_MULTIMETER_V_VOLTAGE(ID_S_MULTIMETER,V_VOLTAGE);


float batteryVoltage=0;  

void blinkityBlink(uint8_t repetitions) {
  for (int x=0;x<repetitions;x++) {
    digitalWrite(LED_BUILTIN,HIGH);
    wait(20);
    digitalWrite(LED_BUILTIN,LOW);
    wait(100);
    digitalWrite(LED_BUILTIN,HIGH);
    wait(20);
    digitalWrite(LED_BUILTIN,LOW);    
    if (x<(repetitions-1)) {  //skip waiting at the end of the final repetition
      wait(500);
    }
  }
}


void presentation()
{
  // Send the sketch version information to the gateway and Controller
  sendSketchInfo("Motion Sensor", "1.0");

  // Register all sensors to gw (they will be created as child devices)
  present(CHILD_ID, S_MOTION);

  wait(SHORT_WAIT);
  
  present(ID_S_MULTIMETER,S_MULTIMETER,"Electric Station");
  wait(SHORT_WAIT);
}


void setup()
{
  hwInit();
  hwPinMode(LED_BUILTIN,OUTPUT_D0H1);
  hwPinMode(PIR_DETECTION_PIN,INPUT);
  blinkityBlink(2,1);  //Signify end of setup with two quick pulses.
  
  disableNfc();  //remove unnecessary energy drains
  turnOffAdc();  //remove unnecessary energy drains
  activateLpComp();
  motion_change=false;
}



void mySleep(uint32_t ms) {
   mySleepPrepare();  //Take steps to reduce drains on battery current prior to sleeping
   sleep(ms);
}


bool motionDetected=false;
void loop() {

  mySleep(300000);  //sleep for 5 minutes

  if (motion_change) {
    motionDetected=!motionDetected;
    if (motionDetected) {
      digitalWrite(LED_BUILTIN,HIGH);  //turn-on LED to signify motion detected
      send(msg.set("1"));  // motion detected
      wait(SHORT_WAIT);
      send(msg.set("1"));
      delay(500);
      digitalWrite(LED_BUILTIN,LOW);
    }
    else {
      digitalWrite(LED_BUILTIN,LOW);  //turn-off LED to signify motion no longer detected
      send(msg.set("0"));  // send all-clear to prepare for future detections
      wait(SHORT_WAIT);
      send(msg.set("0"));
    }    
    
    NRF_LPCOMP->EVENTS_CROSS=0;
    motion_change=false;
  }
  else { //must be a scheduled wake-up.  Time to report voltage as a heartbeat.
    batteryVoltage=((float)hwCPUVoltage())/1000.0;  //take voltage measurement after transmission to hopefully measure lowest voltage that occurs. 
    send(msg_S_MULTIMETER_V_VOLTAGE.set(batteryVoltage,3));  //send battery voltage with 3 decimal places
  }
}


// * Reset events and read back on nRF52
//* http://infocenter.nordicsemi.com/pdf/nRF52_Series_Migration_v1.0.pdf
 
#if __CORTEX_M == 0x04
#define NRF5_RESET_EVENT(event)                                                 \
        event = 0;                                                                   \
        (void)event
#else
#define NRF5_RESET_EVENT(event) event = 0
#endif


// This must be in one line
extern "C" { void LPCOMP_IRQHandler(void) {motion_change=true; NRF5_RESET_EVENT(NRF_LPCOMP->EVENTS_CROSS); NRF_LPCOMP->EVENTS_CROSS=0; MY_HW_RTC->CC[0]=(MY_HW_RTC->COUNTER+2);}}

The serial log from a wake up event:

849294 MCO:SLP:WUP=-1
849296 TSF:TRI:TPU
849298 NRF5:INIT:ESB
849300 NRF5:STL
849301 NRF5:SND:TO=255,LEN=8,PID=1,NOACK=1
849311 NRF5:SND:END=1,ACK=0,RTRY=4,RSSI=-61,WAKE=10
849316 ?TSF:MSG:SEND,70-70-255-0,s=1,c=1,t=16,pt=0,l=1,sg=0,ft=0,st=OK:0
849373 NRF5:SND:TO=255,LEN=8,PID=2,NOACK=1
849383 NRF5:SND:END=1,ACK=0,RTRY=4,RSSI=-61,WAKE=9
849388 ?TSF:MSG:SEND,70-70-255-0,s=1,c=1,t=16,pt=0,l=1,sg=0,ft=0,st=OK:0
849394 NRF5:RX:LEN=8,NOACK=0,PID=1,RSSI=-63,RX=0
849399 TSF:MSG:READ,0-0-70,s=1,c=1,t=16,pt=0,l=1,sg=0:0
849404 TSF:MSG:ACK
849406 MCO:SLP:MS=300000,SMS=0,I1=255,M1=255,I2=255,M2=255
849411 TSF:TDI:TPD
849413 NRF5:PD

From the gateway at NRF5 power-on:

May 07 14:07:49 DEBUG TSF:MSG:READ,70-70-0,s=255,c=3,t=6,pt=1,l=1,sg=0:255
May 07 14:07:49 DEBUG GWT:TPS:TOPIC=mysensors-out/70/255/3/0/6,MSG SENT

Sometimes it all makes it through, not this time.

Here's the startup log from the NRF5 at the same time:

 __  __       ____
|  \/  |_   _/ ___|  ___ _ __  ___  ___  _ __ ___
| |\/| | | | \___ \ / _ \ `_ \/ __|/ _ \| `__/ __|
| |  | | |_| |___| |  __/ | | \__ \  _  | |  \__ \
|_|  |_|\__, |____/ \___|_| |_|___/\___/|_|  |___/
        |___/                      2.3.1

23 MCO:BGN:INIT NODE,CP=RNNPN---,REL=255,VER=2.3.1
28 TSM:INIT
29 TSF:WUR:MS=0
30 NRF5:INIT:ESB
32 TSM:INIT:TSP OK
34 TSM:INIT:TSP PSM
35 TSM:INIT:STATID=70
37 NRF5:STL
39 TSF:SID:OK,ID=70
40 TSM:FPAR
41 TSM:FPAR:STATP=255
43 TSM:ID
44 TSM:ID:OK
46 TSM:UPL:DISABLED
47 TSM:READY:ID=70,PAR=255,DIS=1
50 NRF5:SND:TO=255,LEN=9,PID=0,NOACK=0
60 NRF5:SND:END=1,ACK=0,RTRY=4,RSSI=-61,WAKE=11
65 ?TSF:MSG:SEND,70-70-255-0,s=255,c=3,t=15,pt=6,l=2,sg=0,ft=0,st=OK:0100
72 NRF5:RX:LEN=9,NOACK=0,PID=1,RSSI=-71,RX=0
76 TSF:MSG:READ,0-0-70,s=255,c=3,t=15,pt=6,l=2,sg=0:0100
81 NRF5:SND:TO=255,LEN=12,PID=1,NOACK=1
92 NRF5:SND:END=1,ACK=0,RTRY=4,RSSI=-61,WAKE=10
96 ?TSF:MSG:SEND,70-70-255-0,s=255,c=0,t=17,pt=0,l=5,sg=0,ft=0,st=OK:2.3.1
103 NRF5:SND:TO=255,LEN=8,PID=2,NOACK=1
113 NRF5:SND:END=1,ACK=0,RTRY=4,RSSI=-61,WAKE=9
118 ?TSF:MSG:SEND,70-70-255-0,s=255,c=3,t=6,pt=1,l=1,sg=0,ft=0,st=OK:255
2124 NRF5:SND:TO=255,LEN=20,PID=3,NOACK=1
2135 NRF5:SND:END=1,ACK=0,RTRY=4,RSSI=-61,WAKE=9
2139 ?TSF:MSG:SEND,70-70-255-0,s=255,c=3,t=11,pt=0,l=13,sg=0,ft=0,st=OK:Motion Sensor
2147 NRF5:SND:TO=255,LEN=10,PID=0,NOACK=1
2158 NRF5:SND:END=1,ACK=0,RTRY=4,RSSI=-61,WAKE=9
2162 ?TSF:MSG:SEND,70-70-255-0,s=255,c=3,t=12,pt=0,l=3,sg=0,ft=0,st=OK:1.0
2169 NRF5:SND:TO=255,LEN=7,PID=1,NOACK=1
2179 NRF5:SND:END=1,ACK=0,RTRY=4,RSSI=-61,WAKE=9
2184 ?TSF:MSG:SEND,70-70-255-0,s=1,c=0,t=1,pt=0,l=0,sg=0,ft=0,st=OK:
2240 NRF5:SND:TO=255,LEN=23,PID=2,NOACK=1
2251 NRF5:SND:END=1,ACK=0,RTRY=4,RSSI=-61,WAKE=9
2256 ?TSF:MSG:SEND,70-70-255-0,s=28,c=0,t=30,pt=0,l=16,sg=0,ft=0,st=OK:Electric Station
2314 MCO:REG:NOT NEEDED
2316 MCO:BGN:STP
3057 MCO:BGN:INIT OK,TSP=1
3059 MCO:SLP:MS=300000,SMS=0,I1=255,M1=255,I2=255,M2=255
3064 TSF:TDI:TPD
3066 NRF5:PD

PORT CLOSED

any hints would be more than welcome, please