Hi everyone,

I've tried to sent and recived data from /dev/ttyUSB0/ using node-red. The port opens but I can't recived nothing. 

the port is configured using "cr" delimiter and trasfer the information in a "msg.payload". Nothing appear when i try to riceved.

do you have already try this connection?

thanks

Hello,

I am also interest to receive data from USB host from Node-red.

I would like to connect a barcode reader which act exactly like a USB keyboard.

If anyone can help on this, I would really appreciate!

Have a good day,

Hugo

bergmanu

Hi, 

unfortunately I do not have such an USB barcode reader. 

Have you tried it with Arduino yet? If yes does it work?

Best regards!

 Hello bergmanu,

I was praying the gods of IOT for you to respond .

The barcode readers actually act like a USB keyboard.

They scan the barcode and send the result in a string and can end it with "Enter" (carriage return).

If you want to test it you can plug a keyboard.

I tried it via Node-Red and also via an Arduino sketch, but I can't find the way to correctly point to the USB host port.

Via Node-Red and serial node I am able to use "ttys0", "ttsy1", "ttsy2" and "ttys3" which are the serial ports of the Arduino shield or the two COM ports, but can't see "ttyUSB0" or anything related to the USB host port.

I tried to install all the USB node I was able to find on Node-Red official website, GitHub or NPM, nothing seems to work.

Do I need to "mount" the USB reader/keyboard before?

I tried to shoot on many directions, but can't figure the right spot.

You help is really appreciate!

Have a good day,

Hugo

Hello Bergmanu,

I also tried the lsusb and find the identifier of the USB keyboard, but did not go as far as you by using it in the serial node.

That's an excellent idea.

I tried it and can see if the keyboard is connect or not, but also cannot see anything getting out of the node. 

bergmanu

For now I do not know how to get the input of the keyboard, but I will clarify this issue.

Please let me know if you find something.

Thanks again for the help!

Hugo

Hi,

I have used iot2040 to sample data from barcode scanner, but i'm using c, not node-red.

maybe following link can help you:

https://www.linuxquestions.org/questions/programming-9/read-from-a-usb-barcode-scanner-that-simulates-a-keyboard-495358/

 Hi HugoD,

HugoD

 The barcode readers actually act like a USB keyboard.

When the barcode scanner acts like an USB keyboard, there won't be any ttyUSB device, because keyboards are of the HID USB device class (HID=human input device) and you will find them under /dev/input.

ttys have multiple purposes in Linux, one is to use them for communication to a physical device (like the ttyUSB), but they are also used for logical consoles, e.g. the text consoles. Every console has an input and an output device, for local consoles the output is typically the screen and the input is the keyboard.

The keyboard is only connected to such a console as long as it has the input focus. When a program like Node-Red is started from an interactive shell, it is attached to the tty of that shell, but normally Node-Red is started as background process without a console. You can change this by starting Node-Red with openvt and assign it directly to a specific console.

A pretty good article about ttys can be found here: http://www.linusakesson.net/programming/tty/

You can try is to attach your "barcode keyboard" to one specific (newly created) tty and use this tty from Node-Red. I haven't found the way how to do this, maybe you will find the answer when looking for the following terms: openvt, attach, keyboard, tty, input device.

Alternatively you can directly use the input device /dev/input/by-path/* and not a tty, but that is harder because you go one abstraction level deeper.

A starting point for the ladder might be these node:

https://flows.nodered.org/node/node-red-contrib-autokey

https://github.com/MattGyver/node-red-contrib-dev-input

The following node will require that Node-Red has the input focus and is not started as background process without any terminal: https://www.npmjs.com/package/node-red-contrib-keypress

To use this node assign a tty to Node-Red. This requires the installation of the "kbd" package which contains the openvt tool. Then adapt the/etc/init.d/launch_node-red.sh to look like this: 

openvt -f -c 7 -s -- /usr/bin/node /usr/lib/node_modules/node-red/red

Using this command should also make it possible to use "/dev/tty" (with no number!) in combination with the serial node.

I haven't tested this now, but I used it some years ago with vdr and lirc which had the same problem.

  Michael

 Hi HugoD

HugoD

 The barcode readers actually act like a USB keyboard.

Some barcode scanners can switch their mode from keyboard emulation to serial (UART) model. Look at the documentation if your model supports this. This would save you lots of trouble.

  Michael

Hi Hugo,

the solution can be so simple, just use the following flow (updated on 2017-12-07):

[{"id":"df929f54.5d2f2","type":"tab","label":"Flow 1"},{"id":"aebc0187.f5d95","type":"exec","z":"df929f54.5d2f2","command":"cat /dev/tty1","addpay":false,"append":"","useSpawn":true,"timer":"999999","name":"","x":257.1000061035156,"y":103.28750991821289,"wires":[["20e807fd.f2be98"],[],["9e6325c4.e01e38","20e807fd.f2be98"]]},{"id":"20e807fd.f2be98","type":"debug","z":"df929f54.5d2f2","name":"","active":true,"console":"false","complete":"payload","x":430.10001373291016,"y":91.00000953674316,"wires":[]},{"id":"12c5e279.15b0ee","type":"inject","z":"df929f54.5d2f2","name":"","topic":"","payload":"","payloadType":"date","repeat":"","crontab":"","once":true,"x":107.10000610351562,"y":77.00000381469727,"wires":[["aebc0187.f5d95"]]},{"id":"9e6325c4.e01e38","type":"switch","z":"df929f54.5d2f2","name":"retrigger on timeout","property":"$boolean(msg.payload)","propertyType":"jsonata","rules":[{"t":"false"}],"checkall":"true","outputs":1,"x":253.10000610351562,"y":249.80003261566162,"wires":[["aebc0187.f5d95"]]}]

It uses the node "advanced/exec" with the command "cat /dev/tty1", sets the flag useSpawn=true , the timeout to the greatest possible value 999999 and clears the flag "Append msg.payload"=false.

At the first output of the exec node you will get any keyboard input from /dev/tty1 which includes the input from the barcode reader.

When you get the return-code of the command from output 3, you have to send another input message to start the command again. To avoid endless loops with fast respawning processes, I only do this when the command exists with 0 or null as return code.

On tty1 there is a "getty" running which you should disable. Edit the file /etc/initab and add a # before this line: 

1:12345:respawn:/sbin/getty 38400 tty1

 so it should look like this: 

#1:12345:respawn:/sbin/getty 38400 tty1

Otherwise the getty will consume your first input.

After saving the file, either reboot the IoT2000 or execute the following command to reload the inittab: 

telinit q

   Michael