# Ign8 ModbusRTU serial port access on ARM hardware - Disconnected and jSerialComm.SerialPort error

**URL:** <https://forum.inductiveautomation.com/t/ign8-modbusrtu-serial-port-access-on-arm-hardware-disconnected-and-jserialcomm-serialport-error/38226>\
**Category:** Ignition\
**Created:** [August 31, 2020, 10:25pm UTC](https://forum.inductiveautomation.com/t/ign8-modbusrtu-serial-port-access-on-arm-hardware-disconnected-and-jserialcomm-serialport-error/38226 "2020-08-31T22:25:08Z")\
**Posts on this page:** 12\
**Page:** 1

<div class="post-metadata">

**Author:** ![thebaldgeek](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/thebaldgeek/32/17760_2.png) [@thebaldgeek](https://forum.inductiveautomation.com/u/thebaldgeek)\
**Post date:** [August 31, 2020, 10:25pm UTC](https://forum.inductiveautomation.com/t/ign8-modbusrtu-serial-port-access-on-arm-hardware-disconnected-and-jserialcomm-serialport-error/38226/1 "2020-08-31T22:25:08Z")

</div>

I have installed full Ignition 8.0.15 on some ARMV71 hardware.  
Everything seems to be working well other than the ModbusRTU serial port driver module.

The device simply shows as ‘disconnected’.

The path to the serial devices is correct.

```auto
user@lcben:/dev$ ls |grep USB
ttyUSB0

```

![image.png](https://us1.discourse-cdn.com/inductiveautomation/original/3X/6/7/674e3c26ba8d7c6917dc7af8e65206710d1c0aa6.html)

There are no errors in the Ignition log, but there are in Connections-\>Devices. (But only when I use Trace level).

![image.png](https://us1.discourse-cdn.com/inductiveautomation/original/3X/0/5/05bdff42b1ea362eaebac93c43142101cd9adea1.html)

The first line seems to be the important one.

**java.io.IOException: java.lang.NoClassDefFoundError: Could not initialize class com.fazecast.jSerialComm.SerialPort**

Looking at StackOverflow etc point to the fact that the jSerialComm does not have permissions to the serial port.

Apparently this is most often caused by the user that Ignition is running as is not a member of the ‘dialout’ group.

![image.png](https://us1.discourse-cdn.com/inductiveautomation/original/3X/f/e/fedde7de28f31e78552fe5cb346be3aa7bc04a2d.html)

When I check the user that is running Ignition, I find it is ‘root’.

```auto
user@lcben:/dev$ ps aux |grep ignition
root 4540 0.1 0.1 13324 2832 ? Sl 09:59 0:10 /opt/ignition/./ignition-gateway

```

When I check what groups ‘root’ is a member of, I find it is not a member of any.

As such I edited `/etc/group` and added ‘root’ to the ‘dialout’ group and rebooted the computer.

Ignition still shows the same ‘Disconnected’ error and the same Java error in the log.

With that, I am at a bit of dead end.

If you have any pointers, I am all ears.

Thanks for you help.

---

<div class="post-metadata">

**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\
**Post date:** [August 31, 2020, 10:36pm UTC](https://forum.inductiveautomation.com/t/ign8-modbusrtu-serial-port-access-on-arm-hardware-disconnected-and-jserialcomm-serialport-error/38226/2 "2020-08-31T22:36:14Z")

</div>

Do you have the Serial Support Gateway module installed?

---

<div class="post-metadata">

**Author:** ![thebaldgeek](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/thebaldgeek/32/17760_2.png) [@thebaldgeek](https://forum.inductiveautomation.com/u/thebaldgeek)\
**Post date:** [August 31, 2020, 10:59pm UTC](https://forum.inductiveautomation.com/t/ign8-modbusrtu-serial-port-access-on-arm-hardware-disconnected-and-jserialcomm-serialport-error/38226/3 "2020-08-31T22:59:01Z")

</div>

Yes. Without it, I don’t even get the option for ModbusRTU devices  
(Had to have some help to figure that one out as well!)

---

<div class="post-metadata">

**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\
**Post date:** [August 31, 2020, 11:26pm UTC](https://forum.inductiveautomation.com/t/ign8-modbusrtu-serial-port-access-on-arm-hardware-disconnected-and-jserialcomm-serialport-error/38226/4 "2020-08-31T23:26:05Z")

</div>

Can you upload your Ignition logs somewhere and tell me more about what Linux distro this is? What’s the output of `uname -a`?

---

<div class="post-metadata">

**Author:** ![thebaldgeek](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/thebaldgeek/32/17760_2.png) [@thebaldgeek](https://forum.inductiveautomation.com/u/thebaldgeek)\
**Post date:** [August 31, 2020, 11:50pm UTC](https://forum.inductiveautomation.com/t/ign8-modbusrtu-serial-port-access-on-arm-hardware-disconnected-and-jserialcomm-serialport-error/38226/5 "2020-08-31T23:50:12Z")

</div>

```auto
uname -a
Linux lcben 4.1.15-rt18-nxtio-2.1.0+g57c90e9 #2 SMP PREEMPT RT Mon Jul 13 18:48:35 PDT 2020 armv7l GNU/Linux

```

You can download the logs from here; [https://www.dropbox.com/t/cygxlhuDjp3M3cmQ](https://www.dropbox.com/t/cygxlhuDjp3M3cmQ)

Thanks very much for your time to look at this.

---

<div class="post-metadata">

**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\
**Post date:** [August 31, 2020, 11:52pm UTC](https://forum.inductiveautomation.com/t/ign8-modbusrtu-serial-port-access-on-arm-hardware-disconnected-and-jserialcomm-serialport-error/38226/6 "2020-08-31T23:52:48Z")

</div>

That doesn’t seem to include Ignition logs. You’ll have to download them off the logs page in the gateway or gather up the wrapper.log files wherever it’s installed.

---

<div class="post-metadata">

**Author:** ![thebaldgeek](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/thebaldgeek/32/17760_2.png) [@thebaldgeek](https://forum.inductiveautomation.com/u/thebaldgeek)\
**Post date:** [August 31, 2020, 11:55pm UTC](https://forum.inductiveautomation.com/t/ign8-modbusrtu-serial-port-access-on-arm-hardware-disconnected-and-jserialcomm-serialport-error/38226/7 "2020-08-31T23:55:26Z")

</div>

Oh, thats odd.  
I clicked this icon here;

 ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/c/e/ce7c9fbc82a325b0dcb6ae6c1fe91d319e942516.png)

Where did I go wrong?

EDIT. Ah, I see, Windows has a file type assigned to that extension, My bad… Here they are;

> **[Transfer - Dropbox](https://www.dropbox.com/t/VG6uy955pLucj4YP)**
>
> Dropbox is a free service that lets you bring your photos, docs, and videos anywhere and share them easily. Never email yourself a file again!

---

<div class="post-metadata">

**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\
**Post date:** [September 1, 2020, 12:03am UTC](https://forum.inductiveautomation.com/t/ign8-modbusrtu-serial-port-access-on-arm-hardware-disconnected-and-jserialcomm-serialport-error/38226/8 "2020-09-01T00:03:14Z")

</div>

Hmm… I need the wrapper.log files too…

I don’t know how or where Ignition gets installed on these grooves. Maybe in /opt/ignition you can find a log directory? Or in /var/log/ignition?

I can’t tell if the serial stuff isn’t on the class path or more likely if it’s failing to load because something about this platform isn’t supported.

---

<div class="post-metadata">

**Author:** ![thebaldgeek](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/thebaldgeek/32/17760_2.png) [@thebaldgeek](https://forum.inductiveautomation.com/u/thebaldgeek)\
**Post date:** [September 1, 2020, 12:48am UTC](https://forum.inductiveautomation.com/t/ign8-modbusrtu-serial-port-access-on-arm-hardware-disconnected-and-jserialcomm-serialport-error/38226/9 "2020-09-01T00:48:15Z")

</div>

Kevin,

Thanks very much for you help.  
Having a LOT of trouble sending the file you need since this discord is super sensitive to spam it seems.  
After accepting Dropbox links, its now flagging them as spam.  
Try this.

Wrapper.log. [https://wetransfer.com/downloads/f8283ad56e1d81566551b64e625e226920200901004543/9b3e30667cb249da54401006ae9131d320200901004619/304c51](https://wetransfer.com/downloads/f8283ad56e1d81566551b64e625e226920200901004543/9b3e30667cb249da54401006ae9131d320200901004619/304c51)

Thanks.

Ben

---

<div class="post-metadata">

**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\
**Post date:** [September 1, 2020, 12:57am UTC](https://forum.inductiveautomation.com/t/ign8-modbusrtu-serial-port-access-on-arm-hardware-disconnected-and-jserialcomm-serialport-error/38226/10 "2020-09-01T00:57:07Z")

</div>

Sorry, my best guess is that the native component of the serial module doesn’t work on the groove epic for some reason.

I’ll have to check around to see if we have one available in the office that we can troubleshoot with.

Until recently there was no ARM support at all in the serial module and I think we really only test it on Raspberry Pi.

---

<div class="post-metadata">

**Author:** ![thebaldgeek](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/thebaldgeek/32/17760_2.png) [@thebaldgeek](https://forum.inductiveautomation.com/u/thebaldgeek)\
**Post date:** [September 1, 2020, 12:58am UTC](https://forum.inductiveautomation.com/t/ign8-modbusrtu-serial-port-access-on-arm-hardware-disconnected-and-jserialcomm-serialport-error/38226/11 "2020-09-01T00:58:23Z")

</div>

As far as I know, you have two of them… so uh… while not good news, you have some on site and its a massive sanity check for me, I was going nuts trying to figure out what was happening (or not happening as the case may be).

---

<div class="post-metadata">

**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\
**Post date:** [September 1, 2020, 7:08pm UTC](https://forum.inductiveautomation.com/t/ign8-modbusrtu-serial-port-access-on-arm-hardware-disconnected-and-jserialcomm-serialport-error/38226/12 "2020-09-01T19:08:41Z")

</div>

For anybody that stumbles upon this in the future, the issue is the same as currently prevents running on (some versions of?) RPi: the version of GLIBC needs to be at least 2.28.

This is something we think we can resolve in a future release, though.