Differential pair to wireless communication

[BrettK]

Hi Folks,

This is my first post, I hope it makes sense.

I have some pre existing equipment that communicates bi-directionally over a differential pair via half duplex with RS485 devices.

My question is, how might I go about converting these devices to communicate wirelessly?

I have considered the 433MHz wireless modules because I have several spare, and the range required is not huge, maybe 10m (30') ish almost max.

I thought about brreaking into the non inverting (A) output of the 485 device and feeding that to my transmitter. Then using a (input common) non inverting and inverting buffer at the other end between the receiver to provide the inverted and non inverted inputs to the 485 chip. Here I would use two modules at differing frequencies for the differing transmission directions. However I found when I rigged this up without the wireless modules, just trying to use a single wire in place of the wireless the transmission could not be established.

Subequently, I have thought about using the inputs to the 485, D_I, D_E, R_E| and R_O and using these to drive my wireless modules. D_E and R_E| are supplied by the same pin of the uC, just operaing in complementary fashion, D_I and R_O each being attached to their own uC pins.

I propose to connect D_I and R_O to the relevant pins of my wireless modules and use D_E to power the transmitters and R_E| to control the power to the receivers, thus I will have bi-directional half duplex communication over the wireless modules. - Is this likely to work? I am not sure how the two devices will know how to toggle the state of their enable pin.

Can anyone out there confirm that my ideas might work, or have a better idea as to how I might achieve my goal?

Regards,
Brett.

[poorchava]

I'd use a dedicated RS485<UART> converter chip. You can then either use some transparent communication mode if your module has such capability or use a direct modulation input to the RF IC.

[David_AVD]

How about a pair of these modules off eBay ?

I recently tested the RS232 version and it works quite well.