5 PCS RS-485 MAX485 Transceiver Chip Module TTL to RS-485 Module SCM Development Board

I had a WS2811 12V led strip that was connected to the controller about 30 ft away using sprinkler wire to transmit data. The length was too long and the signals were getting corrupted, so these modules came really handy. One was wired into the control box as the transmitter, the other into the box containing the led strip and set up as a receiver.Look for Arduino Nano TTL to RS485 and wire accordingly. No issues with signal degradation after installing a pair of these.

This helped me control my DMX devices with an ESP-32!

First things first: I haven't tested all five of mine, yet.I bought these to wire up to a raspberry pi, to integrate into the RS-485 bus of my HVAC unit. It wasn't as 'easy' as I'd have liked it to be.I think doing something like this with an arduino (I think I have one in this desk drawer somewhere...) would probably be a bit easier, but alas I haven't found an existing software stack for the HVAC system for an arduino. This being my first time working with RS485, I figured I'd be better off sticking with the 'standard' bits.Some things to note, if you're trying to do what I did with a raspberry pi...I found some wiring diagrams online, which were... more or less confusing as heck. Most of them had the DE and RE lines tied to GPIO pins (23/34 or bonded on GPIO18), and the DI and DO lines tied to the raspberry pi UART TX and RX (GPIO 14 / 15).For starters, let's talk about the UART. You'll need to disable the serial terminal (in /boot/cmdline.txt) defined as a linux kernel param. In raspbian, there's the 'raspi-config' tool for this. BUT: you'll need to make sure that /boot/config.txt has 'uart_enable=1', for the /dev/ttyAMA0 driver to pick up the UART and publish the device.Once you have your kernel params and config set properly, you'll probably try to connect your device to the 485 bus. If this bus happens to be your HVAC system, you may want to pick a comfortable day to work on this... because...Upon bootup to a minimal raspbian install, those GPIO pins bound to DE and RE are both HIGH, putting the 485 device into transmit mode, and essentially interrupting the existing traffic on the bus. In the case of a Carrier/Bryant/Infinity HVAC system, this causes a 'bus communication error' and the entire HVAC will basically suspend all function until you remove your device from the bus. Fun times.If all you want to do is read the bus traffic, you can wire the DE/RE pins to ground.If you want to write to it in a controlled manner, we really ought not be using GPIOs to trigger this. There's been minimal documentation I could find on this, but what I have found mentions that I should tie the DE/RE to the TX pin of my UART and use a latch-type circuit (a 555 timer would be perfect for this) to drive the DE/RE pins high when TX goes high, hold them just long enough for the bit to transmit before resetting.

It makes full use of the transceiver chip and brings out the enable signal to support half-duplex.

There are several better RS485 to TTL boards out there. Keep looking.

Did exactly what I needed it to, connect two Arduino boards over long serial lines to do half duplex communication. Tie the DE/RE pins together, and attach to a digitial out on the arduino. Tie the TX/RX to the arduino uart. Drive a high/low after a delay allowing bootloader to function as normal, and provide the ability to select TX/RX from within your program. Layout of VCC/GND pins could be a bit more convenient if they were not on the same header as the A/B bus.

First impressions are everything. As shown in the picture, this module is not compatible with a single breadboard. I had high school electronics in the 80's, and this standard has not changed.To make this work, I have to dismantle my project, move the breadboards, and make it work by straddling two. Set me back days.Would not recommend this product, or manufacturer.

I bought these to communicate with a pair of PZEM-016 modules, and then one of my PZEMs died so I returned them both and now I'm down to repurposing these for high-reliability long-range inter-Arduino communication. Which they'll do, of course, because RS485 is funny that way.I have no particular complaints about these adapters. Oh, they could be much smaller, but they probably don't really need to be. They'd be nicer (better) if they were optically isolated, but that would also make them more expensive.