This prototype is a total replacement of line driver IC & works very well. Used discrete components in place of line driver ICs. I’ve taken reference from Sparkfun tutorial https://www.sparkfun.com/tutorials/215
I have used USB to TTL converter (CP2102) module for interfacing with laptop. Now when I prototyped the circuit it was not working. I wondered what’s going on.
After replacing components & some tweaking I had found out that it’s the transistor who is responsible for jam. Actually every transistor has beta (current amplification factor) value which changes from transistor to transistor. So I replaced PNP transistor base resistor with a potentiometer of 10k value.
Then putting RS232 port with hyperterminal in loop test mode I started varying pot value, then suddenly at a particular value the hyperterminal window started receiving data sent from send tab. What a AHA moment!!!!!!!!
The perfect phenomena is that it even works at highest baud rate.
Now it’s time to make it a perfect finished device. Means I need to solder component to avoid being fragile, and use anything I need to test, interfacing with any other component. I can use it as a USB-RS232 converter adapter.
This is how the finished device looks like.