Ardunio / ESP8266 / Hardware

ESP8266 JSON Weather Display

by linuxgeek · Published January 2, 2015 · Updated June 18, 2015

This is my first attempt to receive data with an Arduino and the ESP8266 WiFi-Module. This program is based on the example by Seedstudio, and displays weather data on a small TFT display.

The JSON

The weather updates can be requested as JSON data from

http://api.openweathermap.org/data/2.5/weather?id=2925533

This was the result got from the website

{"coord":{"lon":8.68,"lat":50.12},"sys":{"message":0.0037,"country":"DE","sunrise":1420183442,"sunset":1420212885},"weather":[{"id":501,"main":"Rain","description":"moderate rain","icon":"10d"}],"base":"cmc stations","main":{"temp":275.405,"temp_min":275.405,"temp_max":275.405,"pressure":1004.48,"sea_level":1039.53,"grnd_level":1004.48,"humidity":96},"wind":{"speed":6.69,"deg":239.001},"clouds":{"all":92},"rain":{"3h":4},"dt":1420188399,"id":2925533,"name":"Frankfurt am Main","cod":200}

{"coord":{"lon":8.68,"lat":50.12},"sys":{"message":0.0037,"country":"DE","sunrise":1420183442,"sunset":1420212885},"weather":[{"id":501,"main":"Rain","description":"moderate rain","icon":"10d"}],"base":"cmc stations","main":{"temp":275.405,"temp_min":275.405,"temp_max":275.405,"pressure":1004.48,"sea_level":1039.53,"grnd_level":1004.48,"humidity":96},"wind":{"speed":6.69,"deg":239.001},"clouds":{"all":92},"rain":{"3h":4},"dt":1420188399,"id":2925533,"name":"Frankfurt am Main","cod":200}

The Module

This Version has two LEDs, one for Power and another one which is connected to the TX-Pin. It runs at 3.3 Volt and the serial port is set to a data rate of 115200 baud. The CH_PD-Pin has to be high. After a reset, the module sends the following data:

AT+RST
OK
 
 ets Jan  8 2013,rst cause:4, boot mode:(3,6)
 
wdt reset
load 0x40100000, len 24236, room 16
tail 12
chksum 0xb7
ho 0 tail 12 room 4
load 0x3ffe8000, len 3008, room 12
tail 4
chksum 0x2c
load 0x3ffe8bc0, len 4816, room 4
tail 12
chksum 0x46
csum 0x46
 
ready

AT+RST

ets Jan 8 2013,rst cause:4, boot mode:(3,6)

wdt reset

load 0x40100000, len 24236, room 16

tail 12

chksum 0xb7

ho 0 tail 12 room 4

load 0x3ffe8000, len 3008, room 12

tail 4

chksum 0x2c

load 0x3ffe8bc0, len 4816, room 4

tail 12

chksum 0x46

csum 0x46

ready

Wiring

The wiring is quite simple. The wifi-module needs just two wires for power and two for the serial interface. As a display i used a 1.8″ (45.72 mm) TFT-display that is connected via SPI.

Arduino	ESP8266 Module	Display Module
3.3V	VCC & CH_PD
5V		VCC
GND	GND	GND & BKL
0 (RX)	TX
1 (TX)	RX
8		RESET
9		RS
10		LCD CS
11		MOSI
13		SLCK

The Program

I changed the source code from Seedstudio a little bit, because at 115200 baud the 64 Byte uart-buffer from the Arduino fills up very fast. But overall the program is really simple.

#include <SoftwareSerial.h>
#include <JsonParser.h>
 
#define cs   10  // Pins for the display
#define dc   9
#define rst  8
 
#include <Adafruit_GFX.h>    // Core graphics library
#include <Adafruit_ST7735.h> // Hardware-specific library
#include <SPI.h>
 
Adafruit_ST7735 tft = Adafruit_ST7735(cs, dc, rst);
 
using namespace ArduinoJson::Parser;
 
#define SSID "<ssid>" // insert your SSID
#define PASS "<password>" // insert your password
#define LOCATIONID "2925533" // location id
#define DST_IP "188.226.224.148" //api.openweathermap.org
SoftwareSerial dbgSerial(2, 3); // RX, TX for debugging
JsonParser<32> parser;
 
void setup()
{
  Serial.begin(115200);
  Serial.setTimeout(5000);
  dbgSerial.begin(9600); // for debuging
  dbgSerial.println("Init");
  tft.initR(INITR_BLACKTAB);
  tft.setRotation(1);
  tft.fillScreen(ST7735_BLACK);
  tft.setCursor(2, 2);
  tft.setTextColor(ST7735_WHITE);
  Serial.println("AT+RST"); // restet and test if module is redy
  delay(1000);
  if(Serial.find("ready")) {
    dbgSerial.println("WiFi - Module is ready");
    tft.println("WiFi - Module is ready");
  }else{
    dbgSerial.println("Module dosn't respond.");
    tft.println("Module dosn't respond.");
    tft.println("Please reset.");
    while(1);
  }
  delay(1000);
  // try to connect to wifi
  boolean connected=false;
  for(int i=0;i<5;i++){
    if(connectWiFi()){
      connected = true;
      tft.println("Connected to WiFi...");
      break;
    }
  }
  if (!connected){
    tft.println("Coudn't connect to WiFi.");
    while(1);
  }
  delay(5000);
  Serial.println("AT+CIPMUX=0"); // set to single connection mode
}
void loop()
{
  String cmd = "AT+CIPSTART="TCP","";
  cmd += DST_IP;
  cmd += "",80";
  Serial.println(cmd);
  dbgSerial.println(cmd);
  if(Serial.find("Error")) return;
  cmd = "GET /data/2.5/weather?id=";
  cmd += LOCATIONID;
  cmd += " HTTP/1.0rnHost: api.openweathermap.orgrnrn";
  Serial.print("AT+CIPSEND=");
  Serial.println(cmd.length());
  if(Serial.find(">")){
    dbgSerial.print(">");
  }else{
    Serial.println("AT+CIPCLOSE");
    dbgSerial.println("connection timeout");
    tft.fillScreen(ST7735_BLACK);
    tft.setCursor(2, 2);
    tft.setTextColor(ST7735_WHITE);
    tft.println("connection timeout");
    delay(1000);
    return;
  }
  Serial.print(cmd);
  unsigned int i = 0; //timeout counter
  int n = 1; // char counter
  char json[100]="{";
  while (!Serial.find(""main":{")){} // find the part we are interested in.
  while (i<60000) {
    if(Serial.available()) {
      char c = Serial.read();
      json[n]=c;
      if(c=='}') break;
      n++;
      i=0;
    }
    i++;
  }
  dbgSerial.println(json);
  JsonObject root = parser.parse(json);
  double temp = root["temp"];
  double pressure = root["pressure"];
  double humidity = root["humidity"];
  temp -= 273.15; // from kelvin to degree celsius
  tft.fillScreen(ST7735_BLACK);
  tft.setCursor(2, 25);
  tft.setTextColor(ST7735_BLUE);
  tft.setTextSize(2);
  tft.print("Temp: ");
  tft.print((int)temp);
  tft.print(".");
  tft.print((int)((temp-(int)temp)*10));
  tft.println(" C");
  tft.setCursor(2, 55);
  tft.setTextColor(ST7735_GREEN);
  tft.setTextSize(2);
  tft.print("Press: ");
  tft.print((int)pressure);
  tft.setCursor(2, 85);
  tft.setTextColor(ST7735_YELLOW);
  tft.setTextSize(2);
  tft.print("Humidity: ");
  tft.print((int)humidity);
  tft.println("%");
  dbgSerial.println(temp);
  dbgSerial.println(pressure);
  dbgSerial.println(humidity);
  dbgSerial.println("====");
  delay(600000);
}
 
boolean connectWiFi()
{
  Serial.println("AT+CWMODE=1");
  String cmd="AT+CWJAP="";
  cmd+=SSID;
  cmd+="","";
  cmd+=PASS;
  cmd+=""";
  dbgSerial.println(cmd);
  Serial.println(cmd);
  delay(2000);
  if(Serial.find("OK")){
    dbgSerial.println("OK, Connected to WiFi.");
    return true;
  }else{
    dbgSerial.println("Can not connect to the WiFi.");
    return false;
  }
}

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#include <SoftwareSerial.h>

#include <JsonParser.h>

#define cs 10 // Pins for the display

#define dc 9

#define rst 8

#include <Adafruit_GFX.h> // Core graphics library

#include <Adafruit_ST7735.h> // Hardware-specific library

#include <SPI.h>

Adafruit_ST7735 tft = Adafruit_ST7735(cs, dc, rst);

using namespace ArduinoJson::Parser;

#define SSID "<ssid>" // insert your SSID

#define PASS "<password>" // insert your password

#define LOCATIONID "2925533" // location id

#define DST_IP "188.226.224.148" //api.openweathermap.org

SoftwareSerial dbgSerial(2, 3); // RX, TX for debugging

JsonParser<32> parser;

void setup()

{

Serial.begin(115200);

Serial.setTimeout(5000);

dbgSerial.begin(9600); // for debuging

dbgSerial.println("Init");

tft.initR(INITR_BLACKTAB);

tft.setRotation(1);

tft.fillScreen(ST7735_BLACK);

tft.setCursor(2, 2);

tft.setTextColor(ST7735_WHITE);

Serial.println("AT+RST"); // restet and test if module is redy

delay(1000);

if(Serial.find("ready")) {

dbgSerial.println("WiFi - Module is ready");

tft.println("WiFi - Module is ready");

}else{

dbgSerial.println("Module dosn't respond.");

tft.println("Module dosn't respond.");

tft.println("Please reset.");

while(1);

}

delay(1000);

// try to connect to wifi

boolean connected=false;

for(int i=0;i<5;i++){

if(connectWiFi()){

connected = true;

tft.println("Connected to WiFi...");

break;

}

if (!connected){

tft.println("Coudn't connect to WiFi.");

while(1);

}

delay(5000);

Serial.println("AT+CIPMUX=0"); // set to single connection mode

}

void loop()

{

String cmd = "AT+CIPSTART="TCP","";

cmd += DST_IP;

cmd += "",80";

Serial.println(cmd);

dbgSerial.println(cmd);

if(Serial.find("Error")) return;

cmd = "GET /data/2.5/weather?id=";

cmd += LOCATIONID;

cmd += " HTTP/1.0rnHost: api.openweathermap.orgrnrn";

Serial.print("AT+CIPSEND=");

Serial.println(cmd.length());

if(Serial.find(">")){

dbgSerial.print(">");

}else{

Serial.println("AT+CIPCLOSE");

dbgSerial.println("connection timeout");

tft.fillScreen(ST7735_BLACK);

tft.setCursor(2, 2);

tft.setTextColor(ST7735_WHITE);

tft.println("connection timeout");

delay(1000);

return;

}

Serial.print(cmd);

unsigned int i = 0; //timeout counter

int n = 1; // char counter

char json[100]="{";

while (!Serial.find(""main":{")){} // find the part we are interested in.

while (i<60000) {

if(Serial.available()) {

char c = Serial.read();

json[n]=c;

if(c=='}') break;

n++;

i=0;

}

i++;

}

dbgSerial.println(json);

JsonObject root = parser.parse(json);

double temp = root["temp"];

double pressure = root["pressure"];

double humidity = root["humidity"];

temp -= 273.15; // from kelvin to degree celsius

tft.fillScreen(ST7735_BLACK);

tft.setCursor(2, 25);

tft.setTextColor(ST7735_BLUE);

tft.setTextSize(2);

tft.print("Temp: ");

tft.print((int)temp);

tft.print(".");

tft.print((int)((temp-(int)temp)*10));

tft.println(" C");

tft.setCursor(2, 55);

tft.setTextColor(ST7735_GREEN);

tft.setTextSize(2);

tft.print("Press: ");

tft.print((int)pressure);

tft.setCursor(2, 85);

tft.setTextColor(ST7735_YELLOW);

tft.setTextSize(2);

tft.print("Humidity: ");

tft.print((int)humidity);

tft.println("%");

dbgSerial.println(temp);

dbgSerial.println(pressure);

dbgSerial.println(humidity);

dbgSerial.println("====");

delay(600000);

}

boolean connectWiFi()

{

Serial.println("AT+CWMODE=1");

String cmd="AT+CWJAP="";

cmd+=SSID;

cmd+="","";

cmd+=PASS;

cmd+=""";

dbgSerial.println(cmd);

Serial.println(cmd);

delay(2000);

if(Serial.find("OK")){

dbgSerial.println("OK, Connected to WiFi.");

return true;

}else{

dbgSerial.println("Can not connect to the WiFi.");

return false;

}

Conclusion

The program is quite simple and could be extended with more features like a weather forecast. If you have any comments about the source code leave it down below.

Update: There was a bug in the code, which was found by Jody Roth. This is now fixed.

Source Code

The source of this document can be found here

Tags: arduino esp8266 json weather display

ESP8266 JSON Weather Display

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ESP8266 JSON Weather Display

The Module

Wiring

The Program

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