thanks for your answers!

I've searched the web yesterday in the evening for quite a long time and 
stumbled up on this page:


If I got it right, I can use the installed Kernel (Linux beaglebone 
3.8.13-bone71.1) because as of  3.8.13-bone39 RS485 support is built into 
the kernel.

I just did a quick test:

- The beaglebone is connected via USB to my laptop, I ssh into it over said 
- I have a USB-RS485 adapter connected to my laptop as well
- both devices are connected with 2 wires (A&B)
- I've set the jumper to UART4, for both RX and TX
- I also connected the RSE pin to P9_15 which is GPIO48
- UART 4 was activated throug /boot/uEnv.txt 

Using this python 
script https://gist.github.com/Bouni/49a292798e88a7a0956c308b3c9d1190 
(inspired by 
I'm able to communicate over RS485. In my opinion i should be able to 
complete my project with these preconditions.

@William: my ventilation system is completely passiva as far as i know. It 
features a Modbus RTU server from which i can request information or send 
new settings over Modbus RTU.
My Homeautomation system can only handle Modbus TCP. So my plan is to let 
the BB run a Modbus TCP server which translates the TCP requests to RTU and 
send them to the ventilation system.
The answers just go the other way round.

On Thursday, December 1, 2016 at 11:05:54 AM UTC+1, William Hermans wrote:
> On Wed, Nov 30, 2016 at 1:21 PM, Bouni <bo...@owee.de <javascript:>> 
> wrote:
>> Hi,
>> indeed i want to go for Modbus TCP, but unfortunately my ventilation 
>> system has only Modbus RTU. The BB will act as a Gateway between Modbus TCP 
>> and Serial Modbus RTU.
> Does your ventilation system output Modbus over RS485, or is there pure 
> CANBUS output ? What I was proposing, in the case of the later situation. 
> Was to capture the CANBUS output, and directly send that data out over the 
> ethernet port. There are several ways this can be done, and really depends 
> on your programming experience level.
> What I did for our case was "decode" the J1939 / Fastpacket 2000 PGN's in 
> real time. Then parse the data out to an intermediary file. Using POSIX 
> shared memory. Where the second half of the application, took that data, 
> and sent it out via a web app / web socket. All this was done directly on 
> the Beaglebone, in real-time, at 1Mbit frame rate. The application also 
> only used around 1% CPU. Both sides. Anyway, I used the socketCAN library 
> to do all this,
> Another way you could save this data, if you do not need to communicate 
> data back to your ventilation system. Would be to use the socketCAN candump 
> utility. To dump( pipe ) the CANBUS packets directly into Netcat, and then 
> out to a remote system for later parsing . . . The remote system would also 
> have to be running Linux too in this case. As I believe that there is a 
> netcat binary for Windows, but I think this would not be a very smart move.
> However, if your output is Modbus RTU *only*. I'm not very familiar with 
> Modbus, and what your options are. Except, as I recall there is a Linux 
> Modbus development framework of some sort. 

For more options, visit http://beagleboard.org/discuss
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