►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 ►

Conversation

Tue Aug 19 2014, 04:51 PM
allen ndumu
please i will like to know if the problem of speed control of dc motor using keypad and l298 was if yes can i have the complete project send it to the address i really need to see it
Tue Aug 19 2014, 10:47 AM
Amit Bisht
sir i want to have some trending projects on which i could work related to ATmega 16 microcontroller
ExperimenterUK
Sat Aug 16 2014, 04:16 PM
@diligent . create a thread
Sat Aug 16 2014, 03:17 PM
diligent
in assembly langauage programming..
Sat Aug 16 2014, 03:14 PM
diligent
will anyone help me?
Thu Aug 14 2014, 10:24 PM
Amirudin Tone
i help, i need liberary IC 4047 in the proteus. thanks
ExperimenterUK
Thu Aug 14 2014, 03:59 PM
@NARAYANA are you getting an error ?
Tue Aug 12 2014, 11:47 PM
NARAYANA
i am not able to get reg please provide me registration link
Tue Aug 12 2014, 10:32 AM
saloni
sir I was needing literature survey of''ANDROID CONTROLLED SPY ROBOT USING MICROCONTROLLER"
ajay_bhargav
Mon Aug 11 2014, 12:30 PM
@nisargpatel and @NARAYANA please post questions in forum.

Downloads

Comments

hasmukhjain
Wed Aug 20 2014, 06:28 AM
rablo
Tue Aug 19 2014, 10:10 AM
faizhameed
Tue Aug 12 2014, 10:39 PM
ind3siszive
Sun Aug 10 2014, 01:05 PM
snaxxx68
Sat Aug 09 2014, 11:06 AM
[email protected]
Sat Aug 09 2014, 08:58 AM
rajiabdul
Mon Aug 04 2014, 01:31 PM
giash
Sat Aug 02 2014, 04:44 AM

Online

Guests: 53, Members: 0 ...

most ever online: 182184
(Members: , Guests: 182184) on 06 Aug 2010: 01:37 AM

Members: 37496
Newest member: hasmukhjain
Forum Activity
jayachandra Avatar
Posted By jayachandra
Wed Aug 20 2014, 08:11 AM
thanq for reply @hasmukhjain,actually my applicati...
hasmukhjain Avatar
Posted By hasmukhjain
Wed Aug 20 2014, 06:40 AM
Hi Mr jayachandra,I feel ur if statement for switc...
nisargpatel Avatar
Posted By nisargpatel
Wed Aug 20 2014, 01:29 AM
see we are measuring electrical parameters by CT, ...
jayachandra Avatar
Posted By jayachandra
Tue Aug 19 2014, 08:22 AM
HELLOim facing problem with eeprom, i wrote a prog...
ExperimenterUK Avatar
Posted By ExperimenterUK
Sat Aug 16 2014, 04:11 PM
You will have to be more specific about what you a...
nisargpatel Avatar
Posted By nisargpatel
Sat Aug 16 2014, 06:03 AM
Anyone have idea related to AC/DC current measurem...
sairfan1 Avatar
Posted By sairfan1
Wed Aug 13 2014, 01:48 PM
ajay_bhargav Avatar
Posted By ajay_bhargav
Tue Aug 12 2014, 04:34 PM
Usually its better to have a LED driver circuit in...
ajay_bhargav Avatar
Posted By ajay_bhargav
Tue Aug 12 2014, 04:01 PM
There are so many apps available. Did you try a se...
sairfan1 Avatar
Posted By sairfan1
Tue Aug 12 2014, 03:59 PM
thanks, finally advise about brightness issue, I'm...