MAX202

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MAX202

Information

MAX202 is a simple interfacing circuit that makes TTL-leveled signals RS-232 compatible. This allows for devices such as the AVR microcontroller to communicate with a computer or other RS-232 compatible equipment. The large number of capacitors needed is due to the voltage doubler (+10V) and inverter (-10V), these power levels are required to be RS-232 compatible. A stable power source is very important, so if you are experiencing noise or faults in the RS-232 signal you probably need more stabilizing capacitors.

RS-232 and AVR

The circuit on the schematic drawing is MAX232, the capacitor values are not necessary correct for MAX202. Check the datasheet specifications for your device. It's important that the Divide clock by 8 internally fuse is unset.

Projects using MAX202; Serial I/O system.

Source code

The program is written in basic, using Bascom-AVR.

'--------------------------------------------------------------
'                         Thomas Jensen
'--------------------------------------------------------------
'  file: RS232_test
'  date: 27/05/2006
'--------------------------------------------------------------
Dim Name As String * 10
$crystal = 4000000
 
$baud = 9600
Config Lcdpin = Pin , Db4 = Portb.3 , Db5 = Portb.2 , Db6 = Portb.1 , Db7 = Portb.0 , E = Portb.6 , Rs = Portb.7
Config Lcd = 16 * 2
Cls
Cursor Off
 
Print "Welcome to AVR projects"
Lcd "Powerup..."
Lowerline
 
Do
Input "Give your name " , Name
 
Print "Hello " ; Name ; " your serial communication is OK!"
Lcd Name
Loop
 
End