SparkFun Transceiver Breakout - RS-485 Usage ( BOB-10124)

Other Miscellaneous
1

Hello,

I have a situation where one device I have uses RS-232 or TTL (call this device X) and another uses 4-Wire RS485 (call this device Y). I have to get device X to transmit data to device Y, but I don’t ever need device Y to talk back. The voltage levels on all of them are 3.3V. I feel like BOB-10124 is the correct product to use since I only ever need communication in one direction.

I’m thinking the connections should be as follows:

RTS - high

DI - device X TX

RO - device X RX

A - device Y RX+

B- device Y RX -

VCC - 3.3V

GND - GND

Is this correct? What would I do with device Y’s TX+ and TX- lines?

Thanks!

2

That should do the trick, but device X needs to be configured to output TTL serial, RS-232 won’t work. If you don’t need to hear back from device Y, just leave the TX lines for that disconnected.

3

Thank you for your help! Good to know this will work.

4

Quick follow up - what is the idle state for the RS485? Would tying TX+ to 3.3V and TX- to ground permanently be a stable solution so it doesn’t do something random on the device Y side?

5

Idle state is high impedance, RX/TX+ and RX/TX- are essentially disconnected from the bus when not active.

6

Got it, thanks!