Simple TTL to RS232 adapter
During spare time I made quick design of TTL to RS232 adapter, that works with my AVR development board. This adapter helps to connect TTL (Transistor-Transistor Logic) level signals to RS232 interface. TTL side is 9-pin female connector and RS232 sire is male connector.
Unit is powered from target board using power pins.
The RS232 TTL adapter circuit:
Put all the in plastic case and see what I have got:
The inside of the box:
RS232 adapter in action:
Let’s do some test with this RS232 adapter. First of all write some example routine for AVR microcontroller:
Compile this program with WinAVR ad burn to chip.
Then download Bray’s terminal or other terminal software open it and select required baud rate and other settings like parity bits and so on. Start terminal and reset the AVR microcontroller:
Get the results. Everything is working fine.
Download UART AVR project files here. Don’t forget that in this source AVRLIB library is used. So you need to download it in order to be able to build.
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October 20th, 2006 at 4:58 pm
Adding 2 little LED diodes to TX/RX lines helps much. You can use such converter as RS232 line tester - LED flash for transmission.
October 21st, 2006 at 12:11 am
Its good idea. I didn’t think about this. It won’t be hard to add these LEDs to existing board. Thanks.
September 13th, 2007 at 12:28 am
[...] I have made simple RS232 adapter I have decided to improve it a little bit and added status LEDs of TXD and RXD lines. This adapter [...]
September 13th, 2007 at 12:34 am
[...] TTL to RS232 adapter - [Link] Filed in [...]
March 13th, 2008 at 10:47 am
[...] Simple TTL to RS232 adapter - [Link] [...]
March 13th, 2008 at 6:52 pm
We used to make these ourselves, but you can buy these ready made for $40, and the commercial units are self-powered (you don’t need Vcc). Google for 232LPTTL.
-Mark
March 15th, 2008 at 5:21 am
wow, a copy of what can be found in every max232 datasheet, great work
March 15th, 2008 at 12:27 pm
Word press is S*T consider a laxative.
Why buy a 5 - 11 dollar part you’re not using all the features of when you can use a couple transistors and some discrete parts?
http://www.arduino.cc/en/Main/ArduinoBoardSerial
If you need RS232 levels for some reason you can find a blizzard of cheaper alternatives. I’ve used the ADM202, 75c1406 which are under a buck at some suppliers depending on qty.
Another way of getting those levels is a 99 cent wall wart. I’ve done that to and it works for extended runs.
March 17th, 2008 at 11:18 pm
There are professional PCBs/kits and ready built versions around these days:
See:
http://www.tronisoft.com/cat_rs232ioboard.php
See:
http://www.tronisoft.com/rs232info/RS232_To_TTL_Converter.pdf
and for terminal program:
http://www.tronisoft.com/DACIO_RS232_Terminal.zip
Parv