►Introduction

UART (Universal Asynchronous Receiver Transmitter) or USART (Universal Synchronous Asynchronous Receiver Transmitter) are one of the basic interface which you will find in almost all the controllers available in the market till date. This interface provide a cost effective simple and reliable communication between one controller to another controller or between a controller and PC.


►RS-232 Basics

RS-232 (Recommended Standard 232) is a standard for serial binary data signals connecting between a DTE (Data terminal equipment) and a DCE (Data Circuit-terminating Equipment).
Voltage Levels:
The RS-232 standard defines the voltage levels that correspond to logical one and logical zero levels. Valid signals are plus or minus 3 to 25 volts. The range near zero volts is not a valid RS-232 level; logic one is defined as a negative voltage, the signal condition is called marking, and has the functional significance of OFF. Logic zero is positive, the signal condition is spacing, and has the function ON.
So a Logic Zero represented as +3V to +25V and Logic One represented as -3V to -25V.

RS232 Voltage levels


►RS-232 Level Converters

Usually all the digial ICs works on TTL or CMOS voltage levels which cannot be used to communicate over RS-232 protocol. So a voltage or level converter is needed which can convert TTL to RS232 and RS232 to TTL voltage levels.
The most commonly used RS-232 level converter is MAX232. This IC includes charge pump which can generate RS232 voltage levels (-10V and +10V) from 5V power supply. It also includes two receiver and two transmitters and is capable of full-duplex UART/USART communication.

MAX232 Pin description
Fig A. - MAX232 Pin Description
MAX232 typical circuit
Fig B. - MAX232 Typical Connection Circuit



►MAX232 Interfacing with Microcontrollers

To communicate over UART or USART, we just need three basic signals which are namely, RXD (receive), TXD (transmit), GND (common ground). So to interface MAX232 with any microcontroller (AVR, ARM, 8051, PIC etc..) we just need the basic signals. A simple schematic diagram of connections between a microcontroller and MAX232 is shown below

MAX232 connections with microcontroller


In the next part of this tutorial we will discuss programming microcontroller to communicate over UART and software implementation of half duples UART.


◄ Introduction to Serial Communication  |  Microcontroller UART Programming ►
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NexusRevZ Avatar
Posted By NexusRevZ
Wed Jul 30 2014, 02:31 AM
Ok, I have edited the code, it's updated above wit...
NexusRevZ Avatar
Posted By NexusRevZ
Wed Jul 30 2014, 02:10 AM
Oh tahnk you so much for the reply. I will do imme...
ajay_bhargav Avatar
Posted By ajay_bhargav
Wed Jul 30 2014, 01:56 AM
You cannot move and read data from EEPROM immediat...
pravin_35 Avatar
Posted By pravin_35
Wed Jul 30 2014, 12:39 AM
Remove all power connections to the circuit at the...
NexusRevZ Avatar
Posted By NexusRevZ
Tue Jul 29 2014, 09:31 PM
This simple code is test the write and read of EEP...
ExperimenterUK Avatar
Posted By ExperimenterUK
Tue Jul 29 2014, 02:08 PM
Remove all power connections to the circuit at the...
pravin_35 Avatar
Posted By pravin_35
Tue Jul 29 2014, 06:00 AM
Fyiimage with connections
pravin_35 Avatar
Posted By pravin_35
Tue Jul 29 2014, 05:53 AM
another chip is also same problem... i am confused...
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Posted By pravin_35
Tue Jul 29 2014, 01:41 AM
hi guys i found the following link is very useful...
ExperimenterUK Avatar
Posted By ExperimenterUK
Mon Jul 28 2014, 11:17 PM
Link the tx and rx pins on HC06, everything you se...

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NexusRevZ
Tue Jul 29 2014, 09:32 PM
Anyone good in Asm lang?
ajay_bhargav
Mon Jul 28 2014, 12:34 AM
@ Anshu Raj sorry we do not take such requests.
Sun Jul 27 2014, 12:23 AM
Anshu Raj
sir plz send the automatic collage alram bells in 2 hrs bells ring. For microcontroller programme plz sir
ajay_bhargav
Thu Jul 24 2014, 01:06 AM
@R.ABHISHEK where? I dont see it. is it in forum?
Wed Jul 23 2014, 05:49 AM
R.ABHISHEK
sir,pls message on microcontroller 8051 assambly language new program
Wed Jul 23 2014, 05:47 AM
R.ABHISHEK
sir,pls message on 8051 microcontroller assambly language program new quastions
ajay_bhargav
Tue Jul 22 2014, 09:18 AM
@Pragya Android application is taken from google play. Only Author has its source with him. Application is only used in this project.
Tue Jul 22 2014, 04:58 AM
Pragya
plz send me 8051 code and android code for android based device controller via Bluetooth .Here in this project I am using Hc-06 Bluetooth module
Thu Jul 10 2014, 09:57 AM
Caleb
plz someone mail me the source code for that project
Thu Jul 10 2014, 09:57 AM
Caleb
http://www.8051projects.net/download-d188-control-your-pc-tv-remote.html

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