![raspberry pi modbus rtu raspberry pi modbus rtu](https://www.fleaplc.it/images/Articoli/RPI2_ModRTU_Master/Immagini/USBto485.jpg)
I use (and like very much) Realterm as well it is a very versatile program. From the begining I understood that your Instructables was geared to your own product, but Node-RED (as shown in your own images) does not specify your product, but standard "Linux" port names - in that sense it makes it very generic, and means that your Instructables should function correctly. after overcoming some initial difficulties, updating my system, and confirming the functionality of my RS-485 adapters, I was able to make things work like in your Instructables using the generic eBay type RS-485 adapters. If you look at the images in my first post, you can see that I am using ttyUSB0 and ttyUSB1 (not trying to bounce the payload in both directions using the same port). Then when I returned to NodeRED the options available to me were slightly different. Even in spite of keeping my Raspberry Pi IOS (Raspian) up to date, I went ahead and did a " sudo apt-update" and a "sudo apt-upgrade". I think the real problem for me was the actual NodeRED. I had noted that in my original comments. I just wanted to let you know that the Instructables that I commented on is able to work using "generic" eBay converters.
#RASPBERRY PI MODBUS RTU PC#
I've used for my tests Realterm on my PC connected via an simpe USB-RS485 converter to the RS485 HAT on the Raspberry Pi. No needs to write a Python script for this job.
#RASPBERRY PI MODBUS RTU SERIAL#
4.) It is possible to test the function of the on-board uart (and of the USB ports with serial converters too) with a simple terminal program for example Minicom.
![raspberry pi modbus rtu raspberry pi modbus rtu](https://www.jh-electronics-sourcing.com/u_file/2009/products/22/802f31d3c1.jpg)
In this case you have to control the transmit/receive mode of such adaptors via an GPIO port. 3.) Simple TTL to RS485 converter from Ebay comes often without any auto transmitting feature. Please note: You can use /dev/ttyAMA0 to send and receive data to the on-board UART, but the better and more modern term is /dev/serial0 as in the description. This HAT is using the on-board UART of the Raspberry Pi. "A" must be connected to "A" and "B" must be connected to "B" !!!! 2.) This instructable is written for our RS485 HAT. In dÃfference to a RS232 you have not to make a "cross-connection" between the wires for RS485 (half-duplex). Some additional comments about your post: 1.) RS485 is a differtial serial interface. I've tested it today again with the latest Raspberry Pi OS, a Raspberry Pi 4 and our own HAT and it works well on the scretch! Please see my comment at the post of toreplatz too.
![raspberry pi modbus rtu raspberry pi modbus rtu](https://img.bestdealplus.com/ae04/kf/Hfd8a0d4f654c4c0f9939b6c5b7afeac3u.jpg)
Sorry, but I can not understand your problem. As for the TTL to RS-485 adapter, I used a low cost unit from eBay. The TWO "blue" USB to RS-485 that become "ttyUSBx" which I used here are actually pretty nice, They have a Red LED that blinks on Transmit, and a Blue LED that blinks on Receive - very useful for troubleshooting purposes. I also have a node for ttyAMA0 (the on-board UART) which also works when connecting those pins to a TTL to RS-485 Converter. just to confirm that some nodes can work. NOTE: I've added a "Bonjour" payload node for testing purposes. So after more "trying different things", I landed on a working set-up - I'm attaching images of my working system. Following the guidance in this Instructables did not deliver a payload to the "Debug Window" - It really should. Node-RED version: v1.3.3 Node.js version: v10.22.0 Linux 4.19.97-v7+ arm LE = Just like torplatz noted in his message, I struggled to get past step #5 = Note that my own Python script can successfully transfer data from ttyUSB0 to ttyUSB1 (and vice-versa). When "deploying", both of these ttyUSBx ports are seen by Node Red. On the Raspberry Pi one of them becomes ttyUSB0 and the other becomes ttyUSB1. I'm using two USB to RS-485 converters cross connected to each other in a configuration which I can make work correctly using a Python script I wrote. It took a while, but I somehow managed to make it work.