Skip to content

Serial Port Demo

In this demo we demonstrate how to connect an application on ModuCop with a IOU04 COM port. We use a cable to loop the RS232 transmit pin to the receive pin so that all characters sent to the COM port are echoed back.

Preparation steps:

  • Connect a PC and ModuCop to the same network (for example via Ethernet switch or Wi-Fi access point)
  • From the PC, log in to the ModuCop via SSH

Check whether IOU04 COM ports are recognized on ModuCop

ModuCop's Linux image automatically detects COM ports of io4edge devices.

For each detected COM port, a Linux device /dev/tty<device-ID>-com<port> is created. For example, if your IOU04 device ID is S101-IOU04-USB-EXT-1, you will find the following TTY devices:

root@moducop-cpu01:~# ls -l /dev/ttyS101-IOU04-USB-EXT-1*
crw-rw---- 1 root dialout 199, 3 Jul 28 13:33 /dev/ttyS101-IOU04-USB-EXT-1-com1
crw-rw---- 1 root dialout 199, 4 Jul 28 13:33 /dev/ttyS101-IOU04-USB-EXT-1-com2

If you don't see these devices but you see a -can device, clear the CAN configuration to activate the COM ports.

On your ModuCop, run: 

io4edge-cli -d S101-IOU04-USB-EXT-1 set-parameter can-config ""
# Restart to apply parameters
io4edge-cli -d S101-IOU04-USB-EXT-1 restart

Function Test

Create a hardware loop between the RS232 transmit and receive pins of the COM1 RS232 interface. Connect pin 2 and pin 3 of the COM port D-sub connector:

COM loop

Start the minicom terminal program on ModuCop: 

root@moducop-cpu01:~# minicom -D /dev/ttyS101-IOU04-USB-EXT-1-com1 -b 115200
Because we don't have hardware flow control lines, we have to tell minicom not to use hardware flow control: * Press CTRL-A followed by O (O like Omega) 
            ┌─────[configuration]──────┐
            │ Filenames and paths      │
            │ File transfer protocols  │
            │ Serial port setup        │
            │ Modem and dialing        │
            │ Screen and keyboard      │
            │ Save setup as dfl        │
            │ Save setup as..          │
            │ Exit                     │
            └──────────────────────────┘
* Select Serial Port Setup * Press F

Then hardware flow control should be off: 

F - Hardware Flow Control : No
Press two times ESC and you are back in the main screen of minicom.

Now type some characters, and you should see that the characters are echoed back due to the hardware loop.

Welcome to minicom 2.7.1

OPTIONS: I18n
Compiled on Apr 18 2017, 09:55:23.
Port /dev/ttyS101-IOU04-USB-EXT-1-com1, 13:45:27

Press CTRL-A Z for help on special keys

dddddddddddd..ffffdddddddddddddddd

To leave minicom, type CTRL-A, followed by x.