still unsolved, but workaround by replacing the onewire with a DHT22 
this is my sketch:
// Gateway MySensors on NodeMCU with some Devices
// OneWire for DS18B20
// Bounce for S_DOOR (Rain Sensor)
#define MY_DEBUG
#define MY_BAUD_RATE 115200
#define MY_RADIO_NRF24
// #define MY_GATEWAY_SERIAL
#define MY_GATEWAY_ESP8266
#define MY_ESP8266_SSID "myWiFi"
#define MY_ESP8266_PASSWORD "******"
#define MY_ESP8266_HOSTNAME "sensor-gateway"
#define MY_PORT 5003
#define MY_GATEWAY_MAX_CLIENTS 3
#include <ESP8266WiFi.h>
#define MY_INCLUSION_MODE_FEATURE
#include <MySensors.h>
#include <SPI.h>
#include <DallasTemperature.h>
#include <OneWire.h>
#define COMPARE_TEMP 1 // Send temperature only if changed? 1 = Yes 0 = No
#define ONE_WIRE_BUS D1 // Pin where dallase sensor is connected
#define MAX_ATTACHED_DS18B20 5
unsigned long temp_Sleep = 30000; // Sleep time between reads (in milliseconds)
unsigned long temp_nTime;
OneWire oneWire(ONE_WIRE_BUS); // Setup a oneWire instance to communicate with any OneWire devices
DallasTemperature sensors(&oneWire); // Pass the oneWire reference to Dallas Temperature.
float lastTemperature[MAX_ATTACHED_DS18B20];
int numSensors=0;
bool receivedConfig = false;
bool metric = true;
// Initialize temperature message
MyMessage msgTemp(0,V_TEMP);
#include <Bounce2.h>
// RAIN Sensor Definitions and settings
#define CHILD_ID 10
#define BUTTON_PIN D4 // Arduino Digital I/O pin for button/reed switch
Bounce debouncer = Bounce();
int oldValue=-1;
MyMessage msgRain(CHILD_ID,V_TRIPPED);
unsigned long cTime; // Current Time
void before()
{
// Startup up the OneWire library
sensors.begin();
}
void setup()
{
// requestTemperatures() will not block current thread
sensors.setWaitForConversion(false);
pinMode(BUTTON_PIN,INPUT);
digitalWrite(BUTTON_PIN,HIGH);
debouncer.attach(BUTTON_PIN);
debouncer.interval(5);
}
void presentation() {
// Send the sketch version information to the gateway and Controller
sendSketchInfo("Temperature Sensor", "1.1");
// Fetch the number of attached temperature sensors
numSensors = sensors.getDeviceCount();
// Present all sensors to controller
for (int i=0; i<numSensors && i<MAX_ATTACHED_DS18B20; i++) {
present(i, S_TEMP);
}
present(CHILD_ID, S_DOOR);
}
void loop()
{
cTime = millis(); // Get current Timing
if ((cTime - temp_nTime) >= temp_Sleep) { // this is supposed to replace the sleep function
sensors.requestTemperatures();
for (int i=0; i<numSensors && i<MAX_ATTACHED_DS18B20; i++) {
float temperature = static_cast<float>(static_cast<int>(sensors.getTempCByIndex(i)));
#if COMPARE_TEMP == 1
if (lastTemperature[i] != temperature && temperature != -127.00 && temperature != 85.00) {
#else
if (temperature != -127.00 && temperature != 85.00) {
#endif
send(msgTemp.setSensor(i).set(temperature,1));
lastTemperature[i]=temperature;
}
}
temp_nTime = millis();
}
debouncer.update();
int value = debouncer.read();
if (value != oldValue) {
// Send in the new value
send(msgRain.set(value==HIGH ? 1 : 0));
oldValue = value;
}
}
if I enter a
Serial.print("Sensors Count over 1W bus: ");
Serial.println(sensors.getDeviceCount());
I got 0 
wirings are ok... I checked with the tester and I get correct voltage (3,3) and impedence (4,7k)
DHT works fine at first try on the same PIN
thanks for the help
ciao
Marco
