iterating serial ports to identify the target device

[faekjarz]

Hey there, enginerds!

I made this thing a few whiles ago and now i'm fed up of manually starting the thing every time. I want to "daemonize" the driving shell script. I want it to be started automatically on boot. I intend to modify the driver script and create a systemd unit file (which i will publish in the project thread).

In my case there are, at times, multiple serial devices (/dev/tty[USB]?*) connected to the host, and i'd like to pick _that one target device_.

The first approach, i thought of is to iterate every /dev/tty**?? (serial port, on Linux), connect to it, read, and expect a certain reply string, e.g. "OhaiIAmTheTargetDevice" …then pick that serial port.

1) Am i taking a detour, or is it the right direction?
2) Is there an industry standard method for iteratively identifying "ttyserial" devices, i'm not yet aware of?
3) Examples, Experiences, HowTos, Guides, Links… anyone?

[Jeroen3]

1) No. Be polite and don't send random stuff to devices you don't know. Instead, listen for announcements.
2) Ask for hardware identification of the USB port. PID/VID should already exclude many ports.
Or don't use virtual com/tty, you can write directly to one or multiple usb endpoints.
3) Libusb?

[BradC]

Here's a good start. This details the old serial plug and play spec and explains how to do it in a manner that most serial devices won't mind or may even be expecting.

http://www.osdever.net/documents/PNP-ExternalSerial-v1.00.pdf

[voltsandjolts]

If you are not adverse to using FTDI:

1/ Program the FTDI with your chosen serial number.
2/ Install the FTDI D2XX driver.
3/ Use FT_OpenEx() with FT_OPEN_BY_SERIAL_NUMBER

[Monkeh]

Hey there, enginerds!

I made this thing a few whiles ago and now i'm fed up of manually starting the thing every time. I want to "daemonize" the driving shell script. I want it to be started automatically on boot. I intend to modify the driver script and create a systemd unit file (which i will publish in the project thread).

In my case there are, at times, multiple serial devices (/dev/tty[USB]?*) connected to the host, and i'd like to pick _that one target device_.

The first approach, i thought of is to iterate every /dev/tty**?? (serial port, on Linux), connect to it, read, and expect a certain reply string, e.g. "OhaiIAmTheTargetDevice" …then pick that serial port.

1) Am i taking a detour, or is it the right direction?
2) Is there an industry standard method for iteratively identifying "ttyserial" devices, i'm not yet aware of?
3) Examples, Experiences, HowTos, Guides, Links… anyone?

Use a device with a unique serial number, employ udev to create a symlink. Sorted.

[faekjarz]

Thanks everyone, so far.
Keep the input flowing, if you like.

Now i'm busy reading the PDF @BradC mentioned …I'm on page 9 now "1.2. Device Implementation Considerations" …interesting…

I'd like to mention @honx on twitter, who mentioned a tool for programming a unique serial into a Prolific PL2303 and using udev.