RS-485 Board Options

Using Arduino Networking, Protocols, and Devices
1

I am now ready to make the next step in the project that will use RS-485 boards. On eBay I found three options: (shield style will not work as Micro, Pro Mini, or Nano may be used)

Sparkfun Board

Sparkfun 485.jpg
Sparkfun 485.jpg1600×1600 165 KB

Basic RS-485 Board

Basic 485.jpg
Basic 485.jpg930×930 84.3 KB

Enhanced RS-485 Board

Enhanced 485.jpg
Enhanced 485.jpg1000×1000 91.4 KB

What is the experience with each?

I see the idle resistors on the basic board, that the Sparkfun board does not have. They all appear to have termination resistors :frowning: .

The bummer with the basic board, is the lack of mounting holes. The Sparkfun and enhanced board have mounting holes.

What is with all the components on the (third) enhanced board? Are they trouble in the making?

2

Hi,

A lot of RS-485 information and examples and code is here:

http://arduinoinfo.mywikis.net/wiki/SoftwareSerialRS485Example

3

Thanks @terryking228. That much I already knew. I am curious on experience with the three different boards, primarily with the third "enhanced" version. I would love to get a schematic of the third, but I expect that is wishful thinking.

4

That much I already knew.

Hi! Figured you did, but 24 other viewers so far might find it helpful... I have found that notes/links I put up 2 years ago or more have been used by people who did some search for info...

RS-485 is a popular subject: I have 25000 hits on that RS-485 page in 2018.

5

I have used the basic RS485 board soldered into breadboards on a number of projects
it is worth getting a USB-RS485 dongle to plug into a PC to help with debugging

6

The "enhanced" board is missing the DE/RE signal. That means this pin is connected to the TX pin which doesn't work well in a noisy environment (in my experience). The so called lightning protection probably won't work for a lightning but might work well for static discharges and other unwanted voltages. I'm wondering what the third chip might be (one is the voltage regulator, the other is the MAX485 or similar).

The "basic" board is OK if you desolder the resistors you don't need.

The Sparkfun board is the most simple of them, you have to add the bus idle state resistors and the RO idling resistor (if you don't compensate for it by code). It's more or less just a SOIC-8 breakout. Unfortunately it contains the terminating resistor, so for intermediate nodes you have to desolder it. The termination also has a rather strange value but it should work nevertheless.

7

No need for a breakout - you can get the MAX485 and similar in easy-to-solder "DIP" package. That plus termination resistor and failsafes, and you're good to go.

8

DaveEvans:
No need for a breakout - you can get the MAX485 and similar in easy-to-solder "DIP" package. That plus termination resistor and failsafes, and you're good to go.

Plus connectors and a fabricating a PCB (though it is very tempting). This is not for a bench top temporary installation.