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I am trying to connect a WiFi module (ESP8266) to a "funduino" development board (Arduino Nano) but I have no success. Since I tried so much schematics I've found on the internet about the connection between them two, I kindly ask here if is anyone who succeed in "pairing" this two devices. I am asking for the schematic and a functional source code.

Regards

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  • Welcome to StackOverflow! What pins and functions do you have at nano which are absent at nodeMcu ? I mean why would you need to use inferrior micro for design at all? why not to use cortex(stm32, etc) instead of atmega? Obvious options for interafcing would be either uart or SPI. what interfaces have you already tried? Commented Jan 14, 2020 at 17:45
  • I am not talking about nodeMcu, but about the ESP8266 simple module like this one amazon.com/DIYmall-ESP8266-ESP-01S-Serial-Transceiver-x/dp/… Commented Jan 14, 2020 at 20:19
  • please incorporate into your question schemas and code which you tested and which did not work for you. Commented Jan 14, 2020 at 20:24
  • One of the sollutions I've tried is this one: i.sstatic.net/nMYiW.png Commented Jan 14, 2020 at 21:01
  • Arduino Nano is a 5V MCU, the GPIO output 5V, while the ESP-01 is a 3V MCU. So connection you shared in the image will sooner damage your ESP-01. You need a voltage divider on Nano's Tx to drop the voltage to 3V before connecting it to ESP-01 Rx. Commented Jan 15, 2020 at 2:22

1 Answer 1

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The ESP-01 by default comes with nonOS SDK bootloader that communicated via AT commands, you can find the complete command set from Expressif here. This is designed for an MCU (like Arduino Nano) to use it purely as an WiFi module rather than using it as a stand-alone MCU (for which it will require NodeMCU SDK).

If you ever upload an Arduino sketch up to the ESP-01, it will erase the AT Command firmware.

Assuming your ESP-01 is still having the AT Command firmware. What @Ben provided is a sketch that allows you to type AT commands via the Serial Monitor to internact with the ESP-01, it is manual, and good for testing if ESP-01 is working (you type AT and press return on Serial Monitor, the ESP-01 will ack with Ok) but not practical as a real application. The minimum commands required to established an WiFi connection with ESP-01 is listed below. 

AT+CIPMUX=1 - Enable single (0) or multiple connection (1) to the web server.
              Multiple connection is a good option if you are repeatedly sending 
              out or reading data from the Internet.

AT+CWMODE=3 - Set WiFi mode: 1 is station mode (ESP8266 is client), 2 is AP mode 
              (ESP8266 acts like a WiFi router where your phone or PC can connect), 
              3 is AP+station mode (make the ESP8266 do both)

AT+CWJAP=“<your-ssid>”,”<your-pw>” - Connect to your WiFi. Provide your SSID name 
                                     and password inside the double qoutes.

AT+CIFSR - This returns the IP address of the module, indicating that it has 
           successfully connected to your WiFi router.

Once the WiFi connection is established, you can further communicate with the ESP-01 via the connection, like accessing a website for example:

AT+CIPSTART=0,"TCP", "www.example.com","80” - Start TCP or UDP connection. The 
                                              0 is the id of the connection.

AT+CIPSEND=0,16 -   Command to tell the module data is ready to be sent. 0 is the 
                    connection id, and 16 is the length of the data to be sent.
                    After this command, the ESP8266 will reply with the “>” 
                    character to tell us that it will be waiting for the data to be 
                    sent. If successful, the module will reply with “SEND OK”

GET / HTTP/1.1 - Send the http header, and other data, etc...

You can write your own sketch to automate those AT commands for interacting with with ESP-01 once you understand the AT commands required for establish a WiFi connection.

Here are two resources that I personally found extremely useful for doing more than connecting to WiFi.

STM32-ESP-01 Web Server - although this is for interfacing with STM32, the main difference is the pin assignment, so you should be able to port to Arduino easily.

MQTT via ESP-01

As for hardware interface, please noted that what @Ben provided is correct in principle, but you need to be aware that the ESP-01(ESP8266 to be precise) is a 3V3 MCU, so the connection is depended on what kind of host board you are using. If you are using Arduino Uno/Nano, both are having a 5V MCU, you will need a voltage divider (two resistors to drop the voltage to 3v3 before connecting to ESP-01) or a level shifter chip at least for the ESP-01 Rx pin to avoid the potential damage to the ESP-01.

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