Serial communication between mbed and Nodemcu

Hey,

I got a problem with the Serialcommunication between mbed and the nodemcu.
The wiring is: Nodemcu rx to mbed tx.

#include "mbed.h"
    Serial nodemcu(p28, NC);
    int main()
    {
        nodemcu.baud(115200);
    while(1) {
            t2.start();
            if(t2.read_ms() > 1000)
            {
            nodemcu.printf("Hello");
            t2.reset();
            }
     }
    }

My problem is if there is no delay about 1second after nodemcu.printf I dont recieve anything on the Nodemcu.

NodeMcu:

    void setup() {
      Serial.begin(115200);
      Serial.println("Starting...");
    }
    void loop() {
      while (Serial.available()) {
        String node = "";
        node = Serial.readString();// read the incoming data as string
        Serial.println(node);
     }
    }

With serial communication I read one byte at time and save to a char array.
I avoid Serial.readString( ) .

Okey,

could you give me an example please?