asyncMqtt - converting an payload to an number

Projects Programming
1

Im using asyncMqtt to subscribe to a payload (a temperature value) and I want to then print this number to a LCD screen. I can serial print the number but I'm unable to work out what code is needed to print the number to screen.
I was using a call back but it seems the asyncmqtt does not have the ability????

void onMqttMessage(char* topic, char* payload, AsyncMqttClientMessageProperties properties, size_t len, size_t index, size_t total) {
  Serial.println("Publish received.");
  Serial.print("  topic: ");
  Serial.println(topic);
  Serial.print("  qos: ");
  Serial.println(properties.qos);
  Serial.print("  dup: ");
  Serial.println(properties.dup);
  Serial.print("  retain: ");
  Serial.println(properties.retain);
  Serial.print("  len: ");
  Serial.println(len);
  Serial.print("  index: ");
  Serial.println(index);
  Serial.print("  total: ");
  Serial.println(total);
  Serial.print("  payload: ");
  Serial.println(payload); 

}
2

do you try lcd.print(payload) ?

3

yeah but not the answer as it will be text not a number. I need to work out how to change it to a number??

4

to which number?
to integer - use atoi() function
to float/double - atof()

5

sorry to ask but do you have any example code?

6 
float temperature = atof (payload);

perhaps you should to add

#include <stdlib.h>

at the beginning of your sketch

7

that give an error cannot convert float to const char........

8

show your code

9

sorry had put the code in incorrectly, seems to be working better now. I have temperature as the value i need.
thanks

10

please mark the problem solved