Help with RS485 interface to arduino from remote sensor

Thread Starter


Joined May 7, 2012
My Sensor interface to the Arduino is only 2 bits so I have attempted to design a 2 bit digital interface with RS485 chips.

The sensor output is a latched logic high or low from a 555 timer. The sensor has a reset circuit that when it receives a low pulse it will resets the 555 output to a low.

I took a shot at designing a rs485 interface using 3 digital output pins and 1 digital input pin. The arduino will set one 485 chip into transmit mode and send either a low or a high pulse to a remote 485 receiver. The receiver will send its RO output to the /RE and DE lines of another 485 chip. This will either enable its DI input or its RO output. The DI input will send the logic state of the latched 555 timer back to another 485 chip near the arduino so the arduino can test if the latch is set or clear and then do something like write a message to the serial lcd display. The RO output will drive a mosfet in effect simulating a switch being closed to ground to be used to reset the latched 555 timer back to a logic low state.

I am attaching a schematic that I think may work.

I would greatly appreciate all comments on whether or not my schematic will accomplish my goal which is:

Remotely read the state of a switch( the latched 555 output) and then remotely reset the switch back to a known logic state.