I had designed a little board to interface USART to RS-485, that has two types of connection: one row of the DIP MAX232, or the ISP header for ATmega64-128-1281-2561 family.
But after few hours of desing, I had decided to improve the circuit, by adding automatic capabilities to the T/R signal, instead of using SCK from the ISP header.
After one hour googling for circuits that automatically switch T/R signal, I didn't find anything insteresting. Only one circuit that uses a simple transistor and few resistors, but that doesn't satisfy me, since I'm not shure that it switches off the trasnceiver too early after the last bit had been sent.
So I must admit that I'm a lazy guy, since I'm asking for suggestions about that.
My first bet would be to add a capacitor between T/R pins and ground or VCC to add some delay.
Has someone experience with this kind of circuits?
Thanks in advance,