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Re: notification when device change in /dev
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Re: notification when device change in /dev


  • Subject: Re: notification when device change in /dev
  • From: Roland King <email@hidden>
  • Date: Thu, 27 Feb 2014 09:47:53 +0800

That's an idea. Not an Arduino, but not dissimilar, it's a UART mapped through a Segger chip which presents as a USB CDC which the kernel grabs and turns into /dev/cu.usbmodem* which required learning about termios and lots of other things I've not had to think about in 20 years.

Kyle, the IOUSB stuff works too, I have that but find there's a delay before the /dev gets created, a random one, and I haven't yet figured out how to work out what device it gets mapped to, hence I thought I'd go backwards, find devices, and check their properties, but it's a great suggestion.

It might be easier to write a user-space driver for the 2 or 3 control functions the CDC device supports (set baud, set stop bits etc) and grab the bytes from USB directly, in fact I think Apple has an example driver and it's CDC. But I've now strayed from Cocoa once we're beyond fsevents.

On 27 Feb, 2014, at 8:07 am, Graham Cox <email@hidden> wrote:

>
> On 27 Feb 2014, at 10:19 am, Roland King <email@hidden> wrote:
>
>> Is there an NSNotification or some other kind of notification you can subscribe to when there's a change in /dev? I'm dealing with an old USB-serial device which creates a cu/tty when inserted (and removed when removed)  and I'd like to get a notification when that happens so I can update UI.
>>
>> I've hunted around the docs but clearly haven't found the right one yet. I wish there were a master list of all system notifications somewhere, would be handy to find them, or rule out that they exist.
>
>
> I don't think there is, but you could use fsevents to watch that directory.
>
> Arduino? I notice that the Arduino IDE notices the addition of cu/tty in /dev when you plug in a board, but then again it only displays that in a menu, so it might just do a scan when it updates its menus.
>
> --Graham
>
>


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References: 
 >notification when device change in /dev (From: Roland King <email@hidden>)
 >Re: notification when device change in /dev (From: Graham Cox <email@hidden>)

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