Serial interface is common requirement for most of the application development. We are discussing on how to do 3.3V to 5V level conversion for converting serial TTL to RS232 level from 3.3V you can use MAX3232 it operates at 3.3V levels.
Jan 01, 2015 Following on from the FTDI + ESP8266 post, if you do not have a FTDI serial adaptor you can use an Arduino. Here is how to set up the Arduino to talk to the ESP8266. I an using a 5V Arduino Nano which of course is 5V. The Esp8266 is a 3.3v device and so I am using a voltage divider to bring the Arduinos 5V down to 3.3v. The previous project could be too complicated to do the simple job of converting Serial connection to a WiFi connection. So I decided to port a project described in the rest of this article written in Arduino. The ported code works on ESP8266 and can be download from here. Dec 16, 2016 Serial communication on pins TX/RX uses TTL logic levels 3.3V. Don’t connect these pins directly to an RS232 serial port; they operate at +/- 12V and can damage your ESP8266 board. Serial is used for communication between the Arduino board and a computer or other devices.
Serial-to-WiFi Tutorial using ESP8266. The ESP8266 is a low cost Serial-to-WiFi module that interfaces nicely to any microcontroller. However, a word of caution - it is highly undocumented (primary reason for writing this document), and more importantly, it is frequently updated and not backward compatible. There are a lot of guides online on how to connect an ESP8266 to an Arduino uno but there’s too much confusion and not enough explanation. So I’m going to give you the quick version along with the details. Connecting the ESP8266 to an Arduino The steps you need to take are simple. This is written. 2.Install the COM/Serial port driver. In order to upload code to the ESP8266 and use the serial console, connect any data-capable micro USB cable to ESP8266 IOT Board and the other side to your computer’s USB port. The new version NodeMCUv1.0 comes with the CP2102 serial chip,you can download and install the driver here.
On ESP8266 we have one hardware serial i.e. GPIO2 (Tx) and GPIO3 (Rx).
Hardware Serial Programming is similar to the Arduino Serial. Remember that few USB to Serial converter does not support higher baud rate. It is better to keep baud rate below 115200.
Serial interface is useful for debugging the programs by sending some debug info to serial.
Hardware Serial Communication
Level conversion 3.3V to 5V
For Level conversion from 3.3V to 5V we need only two components.
Assuming that you have already connected serial with your USB to Serial converter or You are using ESP Witty, Node MCU.
Serial communication on pins TX/RX uses TTL logic levels 3.3V. Don’t connect these pins directly to an RS232 serial port; they operate at +/- 12V and can damage your ESP8266 board.
Serial is used for communication between the Arduino board and a computer or other devices. All ESP boards have at least one serial port (also known as a UART or USART): Serial. It communicates on RX and TX.
You can use the Arduino IDE environment’s built-in serial monitor to communicate with an ESP board. Click the Tools>>Serial monitor button in the toolbar and select the same baud rate used in the call to begin().
Esp8266 Usb Connection
Before we start our program lets understand commonly used serial commands
Serial.begin(9600);
This command is used to initialize serial port with 9600 baud rate. It is used only when you initialize serial i.e. in Setup() or when you want to change the baud rate. Baud rate is number of bits transmitted per second. Higher the baud rate higher the speed of communication.
Use lower baud rate if cable length is more. Standard baud rates are 300, 1200, 2400, 4800, 9600, 19200, 38400, 57600, 115200, 230400, 250000.
Serial.print(65) gives “65”
Serial.print(char(65)) gives “A”, 65 is ASCII code of A
Serial.print(1.23456) gives “1.23”
Serial.print(‘N’) gives “N”
Serial.print(“Hello world.”) gives “Hello world.”
An optional second parameter specifies the base (format) to use; permitted values are BIN (binary, or base 2), OCT (octal, or base 8), DEC (decimal, or base 10), HEX (hexadecimal, or base 16). For floating point numbers, this parameter specifies the number of decimal places to use. For example:
Serial.print(78, BIN) gives “1001110”
Serial.print(78, OCT) gives “116”
Serial.print(78, DEC) gives “78”
Serial.print(78, HEX) gives “4E”
Serial.println(1.23456, 0) gives “1”
Serial.println(1.23456, 2) gives “1.23”
Serial.println(1.23456, 4) gives “1.2346”
Serial.print(“t”); // prints a tab
Serial.print(“n”); // inserts line break
Serial.write();
Writes binary data to the serial port. This data is sent as a byte or series of bytes; to send the characters representing the digits of a number use the print() function instead.
Serial.print(65); gives “65”
Serial.print(char(65)); gives “A”, 65 is ASCII code of A
Serial.write(65); gives “A”, 65 is ASCII code of A
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Serial.available();
Get the number of bytes (characters) available for reading from the serial port. This is data that’s already arrived and stored in the serial receive buffer (which holds 64 bytes).
Serial.read();
Reads incoming serial data as single byte.
Hardware Serial Program for ESP8266
Programming of ESP is same as arduino.
ESP8266 Serial Communication
2 4 6 8 10 12 14 16 18 20 22 24 | ESP8266 Serial Communication The blue LED on the ESP-12 module is connected to GPIO2 (which is also the TXD pin; so we cannot use Serial.print() at the same time) Serial.begin(9600);// Initialize the Serial interface with baud rate of 9600 // the loop function runs over and over again forever if(Serial.available()>0)//Checks is there any data in buffer Serial.print('We got:'); Serial.print(char(Serial.read()));//Read serial data byte and send back to serial monitor else Serial.println('Hello World..');//Print Hello word every one second } |
Results
Open serial monitor and observe the data we get “Hello World…” every second and when we send any data it shows “We got:data”. as shown in below figure.