RS232 to RS485

[rmteo]

[The Master]

So what your saying is scrap the 555 idea and go back to using RTS. I guess that is an option. Ill have to look into how that will affect the software. I know i can easily control RTS in VB using the comm control but i do like to use API for speed. Ive not had the need to use handshaking before so i should probs read up on that.

Thanx for the suggestion and the diagram. Now i see the point in the MAX232 having 2 ins and outs

[Ioannis]

Why not sending some control characters then wait for the start character, dump it and get the next.

Like this:

Send "#######$data"

on PIC side:

Hserin [wait("$"),str mydata\data_bytes]

Ioannis

[The Master]

I suppose thats a possibility. Im using the hardware UART so its a little harder but still possible.

Is there anything faster than a 555? What about bypassing it? I noticed the output from the MAX232 chip seems to be inverted but if i could invert it again and connect it and the 555 through resistors to the MAX485 then it should be a lot faster because it doesnt rely on the 555 to turn it on, the 555 will simply keep it turned on for a short while after the data stops.

I guess the only problem now is that the MAX485 chip might be too slow to react too

[arniepj]

I have used the 485SD9TB converter from BB Electronics with no problems.It does exactly what you are trying to do.Its not cheap,but you can check out the schematic and maybe reproduce the circuit.

[The Master]

Ive tried the RTS method. It takes quite a while to turn on using software. Im only talking a few ms but its still enough to cause problems.

I think a circuit based on that scematic would be best. I dont have any logic gates that i can make a NOT gate out of so i cant test it yet.

I will have a go at the control characters method. That one seems like it should definately work aslong as i can program it properly. At the moment it relies on counting the bytes that arrive. With the control characters 1 or more will be missing.