RS485 types

[Spookster]

Would a smaller 3485 module such as this work?

Im thinking purely from a smaller form factor

[dxoverdy]

I see no reason why not, go for it.

On Thu, 1 Jun 2023 at 01:22, Spookster @.***> wrote:

Would a smaller 3485 module such as this https://www.aliexpress.com/item/1005001579669576.html?spm=a2g0o.detail.1000014.3.5ba93f40QcRJUE&gps-id=pcDetailBottomMoreOtherSeller&scm=1007.40000.326746.0&scm_id=1007.40000.326746.0&scm-url=1007.40000.326746.0&pvid=d57aa898-9240-48a0-b25d-ac516722e698&_t=gps-id:pcDetailBottomMoreOtherSeller,scm-url:1007.40000.326746.0,pvid:d57aa898-9240-48a0-b25d-ac516722e698,tpp_buckets:668%232846%238109%23206&pdp_npi=3%40dis%21NZD%211.3%211.14%21%21%21%21%21%402101efeb16855787532197865e5207%2112000016669641051%21rec%21NZ%215879163 work?

Im thinking purely from a smaller form factor [image: image] https://user-images.githubusercontent.com/982535/242442328-5aeec18d-09a7-4bf9-9c26-48372d201b16.png

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[dc42]

You will need to connect the EN pin of that board to pin D5 of the ESP. Other than that, I think it should work.

The reason is that the board you pictured really does use a MAX3485 chip, whereas the larger red PCBs pictured in this project don't! They use a a MAX13487E chip. That chip has an auto transmit/receive mechanism built into it, whereas the MAX3485 doesn't. Incidentally, the MAX13487 chip is intended for 5V operation, not 3.3V; so anyone using the red board should ideally power it from 5V and use a potential divider between the TXD pin on the red board (which is the receiver output, so should really be called RXD IMO) and the ESP8266 pin to reduce the signal level to 3.3V.

Note, the red boards also have a protection network comprising a 10 ohm resistor and what I think is a 6.8V Zener diode on the A and B pins. It has a 120 ohm termination resistor, but that is not connected unless you add a 0R resistor to the empty resistor position. The board you pictured has no protection and the 120 ohm termination resistor is connected permanently.

[Spookster]

Good information thanks! Yes, EN to D5 does indeed work

[Spookster]

What I ended up with for now. I had to make do with the only rj45 that was available