Weather fetching on Atmega32 + ESP8266 + LCD1602

About

See the full docs! And also see this on git!

Short description

This project tends to implement:

• ESP8266 module messaging from AVR controller
• Basic Http request + JSON parsing
• LCD support

Why it has been made?

Because of the microcontroller exercises we did on our studies.

What does it do?

• Boots up (if you press any key) the avr enters

settings mode and asks for wifi creditentials

• If no key was pressed during boot then normal procedure takes place

• AVR tries to connect to the wifi

• Then connects to openweathermap.com

• Asks politely for weather data for Warsaw

• Then fetches JSON with the most trivial ways

• Displays the data

• And sometimes refreshes the collected data :)

Pinout

Main wirings

The AVR connections are basic and listed below:

'ATMEGA32'   PA0 -> D4   'LCD'
'ATMEGA32'   PA1 -> D5   'LCD'
'ATMEGA32'   PA2 -> D6   'LCD'
'ATMEGA32'   PA3 -> D7   'LCD'
'ATMEGA32'   PA4 -> RS   'LCD'
'ATMEGA32'   PA5 -> RW   'LCD'
'ATMEGA32'   PA6 -> E    'LCD'
'ATMEGA32'   RXD -> TX   'ESP8266'
'ATMEGA32'   TXD -> RX   'ESP8266'
'ESP8266'    EN  -> VCC  'ESP8266'

And of course V0, VCC, GND, VSS, VDD, A, K but they are trivial.

Buttons

And not mentioned in layout two buttons for settings screen:

'ATMEGA32'  PD6  -(BUTTON)->  GND
'ATMEGA32'  PD7  -(BUTTON)->  GND

In settings mode:

• PD6 is used have next character functionality.

• PD7 changes current character.

Schematic of connections (pretty small - try to enlarge with zooming hand):

Notice:

The ESP8266 module was connected to the 5V USB plug. The module is designed to work for 3V but working on higher voltage is possible (as demonstrated in this case).

It's straightforward method and in normal conidtions you should redesign scheme a little and provide 3V voltage source for your wifi module.

You will probably need logic level shifting form 5V (atemga) to 3V (esp8266) or you can just run atmega on 3V (notice that LCD needs standard 5V anyway!)

Mounting

You can mount the wires propably on pcb plate I used universal brakboard that does not require soldering but it's rather a messy pile of cables, huh!

About building

Build process

Warnning!

Before building make sure all it's configured correctly (see configuration for more details)!

To build the project do the following:

• Create release folder e.g. mkdir release

• Go into that folder cd release

• Run CMAKE to generate needed makefiles cmake ..

• Build app using make make

• Optionally update documentation throught make doc

• Optionally setup manually the needed fuse bits using avrdude!

• Flash controller with make upload

• Optionally clean build with make clean

Configuration

Before continouing make sure that USSID and PASSWD Variables in src/main.c are configured to use with your wifi access point.

Then make sure that APIKEY in line with wifi_send is matching apikey for your openweathermap account. And the url is for location desired by you. See openweathermap api documentation for more details :)

The main controller config is placed in CMakeLists.txt file.

Please change these as you wish:

# Variables regarding the AVR chip
set(MCU   atmega32)
set(F_CPU 8000000)
set(BAUD  9600)
set(PROG_TYPE usbasp)
set(PROG_ARGS )

BAUD is not really needed and PROG_ARGS are additional paramters for avrdude.

Basic example config for Atmega328P-PU running (by default) at 1MHz:

# Variables regarding the AVR chip
set(MCU   atmega328p)
set(F_CPU 1000000)
set(BAUD  2400)
set(PROG_TYPE usbasp)
set(PROG_ARGS )

Some source code

This snippet presents piece of source code from main.c (and is good introduction to the project insides as well as wifi.h module):

// Handle ESP8266 events
void wifi_event_handler(int event, const char* input, const int len) {

  switch(event) {
    case WIFI_EVENT_ANY: {
       //
       // You can display the input
       // To provide debug info
       // This kind of event (ANY)
       // is called for any event
       //
       return;
    } break;

    case WIFI_EVENT_ERROR: {
       // We got error!
    } break;

    // ESP8266 is not responding
    case WIFI_EVENT_TIMEOUT: {
       // We got timeout!
    } break;

    // Wifi was connected
    case WIFI_EVENT_WIFI_CONNECTED: {
       // We are conneted to the access point!
    } break;

    // Wifi was disconnected
    case WIFI_EVENT_WIFI_DISCONNECTED: {
       // We are disconneted to the access point!
    } break;

    // Connect to host
    case WIFI_EVENT_CONNECTED: {
       // We are connected to the ip/url specified earlier throug wifi_link_open
    } break;

    // Host sends data
    case WIFI_EVENT_DATA: {
      //
      // Look for JSON data in response
      //
      search_json(weather_descr, input, "description");
      search_json(weather_name, input, "name");

      search_json(weather_data_buf, input, "humidity");
      sscanf(weather_data_buf, "%lf", &weather_humidity);

      search_json(weather_data_buf, input, "pressure");
      sscanf(weather_data_buf, "%d", &weather_pressure);

      search_json(weather_data_buf, input, "temp");
      sscanf(weather_data_buf, "%lf", &weather_temp);


      // We do not need this connection anymore
      wifi_link_close();

      // Format received data
      sprintf(info1, "%s Weather:", weather_name);
      sprintf(info2, "%s | Temp: %.1lf C | Humidity: %.0lf %% | Pressure: %d HPa", weather_name, weather_temp-273.15, weather_humidity, weather_pressure );

      //
      // Display data continously in text shifting manner
      //  
      int shift = 0;
      const int info_len = strlen(info2);
      int cycles = 0;

      while(1) {
         lcd_clrscr();
         lcd_gotoxy(0, 0);
	       lcd_nputs(info1, 16);
	       lcd_gotoxy(0, 1);
	       lcd_nputs(info2+shift, 16);
	       _delay_ms(500);
	       ++shift;
	       if(shift > info_len - 4) {
             shift = 0;
             ++cycles;   
         }
         //
         // End - return to main and then prepare next fetch request
         //
         if(cycles > 15) break;
      }

      lcd_nputs("Update...", 16);
      lcd_clrscr();
    } break;
  }
}


int main(void) {

  // Init UART
  uart_init(UART_BAUD_SELECT(2400, F_CPU));

  // Init buttons

  //
  // ...
  //

  // Init LCD
  lcd_init(LCD_DISP_ON);
	lcd_gotoxy(0, 0);
	lcd_clrscr();

  // Init wifi and connect to the desired network
  lcd_clrscr();
  lcd_puts("Initializing...");
  _delay_ms(1000);
  wifi_init();

  //
  // Check if any button was pressed
  // then go into settings mode :)
  //

  //
  //  ...
  //

  //
  //  Normal boot sequence
  //
  normal_boot:

  // Display greeting on lcd
  lcd_puts("Hello");
  _delay_ms(1000);
  lcd_clrscr();
  _delay_ms(1500);


  lcd_clrscr();
  lcd_puts("Conecting...");
  _delay_ms(1000);

  //
  // Display USSID/PASSWD data on the screen
  //
  lcd_clrscr();
  lcd_puts("ID: ");
  lcd_puts(USSID);
  lcd_puts("\nPASS: ");
  lcd_puts(PASSWD);
  _delay_ms(1500);

  // Try to connect to the access point
  wifi_connect(USSID, PASSWD);

  while(1) {
    // To make sure nothing dumb trash does not come
    // through UART interface
    uart_flush();

    // Connect to openweathermap
    wifi_link_open("TCP", "api.openweathermap.org", 80);

    // Request data from REST api
    wifi_send("GET /data/2.5/weather?q=warsaw&APPID=cf24c94ac2550178e2ea4e970cd0f416 HTTP/1.1\r\nHost: api.openweathermap.org\r\nConnection: keep-alive\r\nCache-Control: max-age=0\r\n\r\n\r\n");

    // Wifi functions will call wifi_event_handler function on any event (it's callback function)
  }

  return 0;
}