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 Modul
I bought this module at Electrodragon. 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:
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| AT+RSTOK ets Jan 8 2013,rst cause:4, boot mode:(3,6)wdt resetload 0x40100000, len 24236, room 16tail 12chksum 0xb7ho 0 tail 12 room 4load 0x3ffe8000, len 3008, room 12tail 4chksum 0x2cload 0x3ffe8bc0, len 4816, room 4tail 12chksum 0x46csum 0x46ready |
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.
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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.orgSoftwareSerial dbgSerial(2, 3); // RX, TX for debuggingJsonParser<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/1.0\r\nHost: api.openweathermap.org\r\n\r\n"; 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. I hope i don’t have to many spelling mistakes in my first English post 
Update: There was a bug in the code, which was found by Jody Roth. This is now fixed.
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