RS485 without a 555

[dhouston]

Hi, I just had a random idea. Ive been using the 555 timer method to automatically switch an RS485 chip from receive to send. I was just thinking though, is the 555 part really needed? Couldnt i just fix the data input pin to high and connect the TX pin from the chip to the pins that change it to a sender (possibly through an invertor). This method would mean it changes to and from sender/receiver faster and requires less components (even if it needs an invertor).

Is there a reason everyone seems to use the 555 method instead of this? Are there any potential problems doing it this way?

The 555 switches from send to receive not receive to send. You could delay 25mS or so before switching the line direction or you could watch the output buffer to see when it is clear (not easy with a software UART) - the 555 does this automatically.