MIO04 Quick-Start-Guide / Serial Demo

Serial Port Demo

In this demo, we’ll demonstrate how to connect an application on a Linux host with a MIO04 COM port. We’ll use a cable to loop the RS232 transmit pin to the receive pin, so that we’ll get all characters back that are sent to the COM port.

The procedure depends on your host system. Select the tab that matches your host:

Access MIO04 COM port from ModuCop

Preparation Steps:

  • Ensure you have configured the network and device ID for the MIO04 as shown above
  • Connect a PC, ModuCop, and MIO04 to the same network, e.g. by using an Ethernet Switch or a Wifi Access Point
  • From the PC, login into the ModuCop via ssh

Check whether MIO04 COM ports are recognized on ModuCop

ModuCop’s linux image is configured to detected COM Ports of io4edge devices automatically.

For each detected COM port, a linux device /dev/tty<device-ID>-com<port> is created. For example, if your MIO04 device ID is MIO04-1, you’ll find the following tty devices:

root@moducop-cpu01: ~# ls -l /dev/ttyMIO04*
crw-rw---- 1 root dialout 199, 3 Jul 28 13:33 /dev/ttyMIO04-1-com1
crw-rw---- 1 root dialout 199, 4 Jul 28 13:33 /dev/ttyMIO04-1-com2

Function Test

Now, let’s make a hardware loop between the RS232 transmit and receive pin of the COM1 RS232 interface. Connect pin 2 and 3 of the COM ports D-Sub connector:

COM Loop

Start the minicom terminal program on ModuCop:

root@moducop-cpu01: ~# minicom -D /dev/ttyMIO04-1-com1 -b 115200

Because we haven’t connected 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 screeen of minicom.

Now type some character, and you should see that the characters are echoed back, due to the hardware loop we have created!

Welcome to minicom 2.7.1

OPTIONS: I18n
Compiled on Apr 18 2017, 09:55:23.
Port /dev/ttyMIO04-1-com1, 13:45:27

Press CTRL-A Z for help on special keys

dddddddddddd..ffffdddddddddddddddd

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

Access MIO04 COM port from any Linux Host

To access the MIO04 COM ports from a linux host, the easiest way is to use the user space program ttynvt that creates a virtual tty device on the host and forwards all host accessed via network to the MIO04.

ttynvt installation

Requirements on linux host:

  • kernel must support FUSE (FUSE_FS=y)
  • libpthread and libfuse must be installed in the root filesystem.
  • git, autoconf, make, gcc installed

Build:

$ git clone https://gitlab.com/ci4rail/ttynvt.git
$ cd ttynvt
$ autoreconf -vif
$ ./configure
$ make

Start ttynvt

In a first terminal, start a temporary instance of ttynvt.

# From the folder where you have built ttynvt
$ sudo src/ttynvt -f -E -M 384 -m 1 -S <ip-address-of-your-device>:10000 -n ttyNVT0

This will create a new device /dev/ttyNVT0

$ ls -l /dev/ttyNVT0
crw-rw---- 1 root dialout 384, 1 Jul 28 16:05 /dev/ttyNVT0

Function Test

Now, let’s make a hardware loop between the RS232 transmit and receive pin of the COM1 RS232 interface. Connect pin 2 and 3 of the COM ports D-Sub connector:

COM Loop

In a second terminal, start picocom terminal program.

Then type some character, and you should see that the characters are echoed back, due to the hardware loop we have created!

$ picocom /dev/ttyNVT0 -b 115200
...
Terminal ready

dddddddddddd..ffffdddddddddddddddd

To leave picocom, type CTRL-A, followed by CTRL-X.