strcmp numerical values on esp8266

Using Arduino Programming Questions
#1

Hi,

Im a complete noob to programming really apart to finding small bits of code, playing with it and trying to understand it.
At the moment i have an esp with Nodemcu FW.
I have the esp subscribed to my mqtt account and receiving feed data between 0.00 and 15.00.

I am trying to get the code to turn on outputs at 5 different levels as the values received increase from 0-15.
The problem i seem to be having is my compare string appears to only be taking note of the 1st digit. (e.g. id 3 if 31 is received). If 31 is received it would turn on my first two outputs but not the others. Where as if 9 is received is would turn 4 of the 5 outputs on.

I would really appreciate some help, I’ve spent hours trolling through the web without finding anything i can truly understand.
Regards :confused:

  Adafruit_MQTT_Subscribe *subscription;
  while ((subscription = mqtt.readSubscription(5000))) {
    if (subscription == &uv_index_feed) {
      Serial.print(F("Got uv index: "));
      Serial.println((char *)uv_index_feed.lastread);
    } else if(subscription == &errors) {
      Serial.print(F("ERROR: "));
      Serial.println((char *)errors.lastread);
    } else if(subscription == &throttle) {
      Serial.println((char *)throttle.lastread);
    } if (strcmp((char *)uv_index_feed.lastread,"0" ) >= 0) {
        digitalWrite(2, LOW);
    } if (strcmp((char *)uv_index_feed.lastread,"3") >= 0) {
        digitalWrite(13, LOW);
    } if (strcmp((char *)uv_index_feed.lastread,"3") < 0) {
        digitalWrite(13, HIGH);
    } if (strcmp((char *)uv_index_feed.lastread,"6") >= 0) {
        digitalWrite(4, LOW);
    } if (strcmp((char *)uv_index_feed.lastread,"6") < 0) {
        digitalWrite(4, HIGH);
    } if (strcmp((char *)uv_index_feed.lastread,"8") >= 0) {
        digitalWrite(5, LOW);
    } if (strcmp((char *)uv_index_feed.lastread,"8") < 0) {
        digitalWrite(5, HIGH);
    } if (strcmp((char *)uv_index_feed.lastread,"11") >= 0) {
        digitalWrite(14, LOW);
    } if (strcmp((char *)uv_index_feed.lastread,"11") < 0) {
       digitalWrite(14, HIGH);
    }
  }

.

Moderator edit: hours looking for a solution, but not a couple of minutes reading the forum posting guidelines?

#2

You should really go back and read what strcmp does.

I wouldn't be doing what you are doing if you are wanting to compare integer values.

#3

Try the [

atoi

](avr-libc: <stdlib.h>: General utilities) function instead. Then you can compare integers, not C strings.

  int value = atoi( (char *)uv_index_feed.lastread );
  if (value == 31)
     ...
#4

-dev
Thank you very much for your help. I'll take a read and look into atoi.
Much appreciated!!

#5