RS232 회로 구성

[펌] http://www.scienceprog.com/alternatives-of-max232-in-low-budget-projects/

 컴퓨터를 기준으로 잡았을때를 말하는 것입니다. 2번이 RX 3번이 TX가 되겠지요..
7번은 RTS 8번은 CTS 입니다.

RS232의 신호 레벨은 Active 상태 일때는 +3V ~ + 15V
inactive 상태 일때는 -3V ~ 15V 입니다.


MAX 232를 이용한 구성입니다.

max232.pdf

Max232 IC is a specialized circuit which makes standard voltages as required by RS232 standards. This IC provides best noise rejection and very reliable against discharges and short circuits. If your project is more advanced and has to reliable you must use specialized RS232 to TTL converter IC’s. As I said Specialized are more expensive than other solutions.

One of such solution is Transistor based interface:

다음과 같이 TR을 이용하여서 구성을 할수 있습니다.
학생이라면 한번은 해볼만 하겠지요?
머 단가를 낮춘다고 사용할수도 있지만 통신에 대한 보장은 할수 있을려나? ㅎㅎ

Transistors can be any general purpose transistors. This circuit is very easy and works without problems. It is cheapest solution as it require couple of transistors and four resistors. Two transistors does a trick to get a negative voltage as required by some PCs. When the PC does not transmit data, its TX pin is stuck to a negative voltage. The negative voltage is picked up from the TX pin and brought back – through resistor R3 – to the PC’s RD pin.

RS232 alternatively can be interfaced using Logic gates. This is handy when your application is using logic elements and there are couple gates left on some IC. As almost every PC can vork with positive-only signals logic gates can provide necessary inversions. For instance using CD4066B CMOS IC:

제너는 4.7V 레벨을 유지 하기 위해서 사용 한거 같내요. 이 구성은 해본 적이 없어서 ㅎㅎ

And of course NAND and NOR circuits: