NodeMCU v1 keeps dropping out

Question

I've created a homebridge server on a Raspberry Pi Zero and have configured it to use my NodeMCU v1 (Esp - 12E Module) as an accessory to control RGB strip lights.

All works normally until you don't use the home kit to control the lights for certain amount of time (~30 seconds). My iPhone says that the accessory is non responsive until I force a command to happen, this after some time activates the accessory and goes back to normal.

Is there a way of keeping the NodeMCU active to HTTP responses all the time?

The code I have used is a mashup of a tutorial I used but I've modified it with some more features. (All coded in Arduino)

//NodeMCU RGB-Controller for Homebridge & HomeKit (Siri)
#include <ESP8266WiFi.h>
#include <math.h>
#define redPin 13 //D7 - Red channel
#define grnPin 12 //D6 - Green channel
#define bluPin 14 //D5 - Blue channel
#define white 5 //D1 - Blue channel
WiFiServer server(80); //Set server port
String readString; //String to hold incoming request
String hexString = "000000"; //Define inititial color here (hex value), 080100 would be a calm warmtone i.e.
int state;
int r;
int g;
int b;
float R;
float G;
float B;
int x;
int V;
///// WiFi SETTINGS - Replace with your values /////////////////
const char* ssid = "xxxxxxx";
const char* password = "xxxxxxx";
IPAddress ip(192,168,1,234); // set a fixed IP for the NodeMCU
IPAddress gateway(192,168,1,1); // Your router IP
IPAddress subnet(255,255,255,0); // Subnet mask
////////////////////////////////////////////////////////////////////
void WiFiStart() { 
 Serial.print("Connecting to ");
 Serial.println(ssid);
 WiFi.begin(ssid, password);
 WiFi.config(ip, gateway, subnet); //Set a fixed IP. You can comment this out and set it in your router instead.
 while (WiFi.status() != WL_CONNECTED) {
 delay(100);
 Serial.print("_");
 }
 Serial.println();
 Serial.println("Done");
 Serial.print("IP address: ");
 Serial.println(WiFi.localIP());
 Serial.println("");
 server.begin(); 
}
void allOff() {
 state = 0;
 analogWrite(redPin, 0);
 analogWrite(grnPin, 0);
 analogWrite(bluPin, 0);
}
//Write requested hex-color to the pins (10bit pwm)
void setHex() {
 state = 1;
 long number = (long) strtol( &hexString[0], NULL, 16);
 r = number >> 16;
 g = number >> 8 & 0xFF;
 b = number & 0xFF;
 r = map(r, 0, 255, 0, 1023); //added for 10bit pwm
 g = map(g, 0, 255, 0, 1023); //added for 10bit pwm
 b = map(b, 0, 255, 0, 1023); //added for 10bit pwm
 analogWrite(redPin, (r));
 analogWrite(grnPin, (g));
 analogWrite(bluPin, (b));
}
//Compute current brightness value
//For serial debugging only
void showValues() {
 Serial.print("Status on/off: ");
 Serial.println(state);
 Serial.print("RGB color: ");
 Serial.print(r);
 Serial.print(".");
 Serial.print(g);
 Serial.print(".");
 Serial.println(b);
 Serial.print("Hex color: ");
 Serial.println(hexString);
 Serial.print("Brightness: ");
 Serial.println(V);
 Serial.println("");
}
void setup(){
 Serial.begin(9600);
 delay(1);
 pinMode(redPin, OUTPUT); //declaration added
 pinMode(grnPin, OUTPUT); //declaration added
 pinMode(bluPin, OUTPUT); //declaration added
 setHex(); //Set initial color after booting. Value defined above
 WiFi.mode(WIFI_STA);
 WiFiStart();
 //showValues(); //Uncomment for serial output
}
void loop() {
 //Reconnect on lost WiFi connection (superfluous - will reconnect anyway)
 if (WiFi.status() != WL_CONNECTED) {
 WiFiStart();
 }
 WiFiClient client = server.available();
 if (!client) {
 return;
 }
 while(client.connected() && !client.available()) {
 delay(1);
 }
 //Respond on certain Homebridge HTTP requests
 if (client) {
 while (client.connected()) {
 if (client.available()) {
 char c = client.read();
 if (readString.length() < 100) {
 readString += c;
 } 
 if (c == '\n') {
 Serial.print("Request: "); //Uncomment for serial output 
 Serial.println(readString); //Uncomment for serial output
 //Send reponse
 client.println("HTTP/1.1 200 OK"); 
 client.println("Content-Type: text/html");
 client.println();
 //On
 if(readString.indexOf("on") >0) {
 setHex();
 Serial.println("on");
 showValues();
 }
 if(readString.indexOf("xw") >0) {
 Serial.println("won");
 analogWrite(white, 1024);
 }
 if(readString.indexOf("yw") >0) {
 Serial.println("woff");
 analogWrite(white, 0);
 }
 //Off
 if(readString.indexOf("off") >0) {
 allOff();
 showValues();
 }
 //Set color
 if(readString.indexOf("set") >0) {
 hexString = "";
 hexString = (readString.substring(9,15));
 setHex();
 //showValues();
 }
 //Status on/off
 if(readString.indexOf("status") >0) {
 client.println(state);
 }
 //Status color (hex)
 if(readString.indexOf("color") >0) {
 client.println(hexString);
 }
 //Status brightness (%)
 if(readString.indexOf("bright") >0) {
 client.println(V);
 }
 delay(1);
 client.stop();
 readString="";
 }
 }
 }
 }
}

Answer 1

You are probably running out of RAM because you are using the String object instead of a fixed-size char[] buffer. This code, in particular:

if (readString.length() < 100) {
 readString += c;
} 

Concatenating String objects using the overloaded plus operator allocates a whole new block of RAM for the new, longer string. It frees the previous memory, but since you keep adding one character at a time, new strings won't be able to be put into the once-used RAM.

You should instead use C-style strings (character arrays) and the standard functions for managing them, such as strnlen() and strncat(), etc. Note, I am suggesting the versions of string functions with a maxlen parameter, which helps avoid bugs due to unterminated strings.

• Gorria24: I can't seem to implement this
• jose can u c: Share what you’ve tried. Thus page has a good overview gammon.com.au/concat
• Gorria24: I had to make a new question as the comment wouldn't let me copy all my changed code: arduino.stackexchange.com/questions/48066/…