Closes USB comms properly to allow communication while booting.

[tcr]

See #346, #291.

Only tested with t2 list for now.

[johnnyman727]

@tcr thanks for working on this!

So we have some infrastructure in place to make sure all Tessel connections get closed. Essentially, every command run will end with controller.closeTesselConnections which ultimately calls tessel.close and that function, if it has a USB connection, will ultimately call USBConnection._close.

It seems as though the significant part of your PR is calling self.epIn.stopPoll before releasing the interface. Can we just include that portion of your PR to have the same effect? It seems like the rest of the PR is just making sure connections get closed which they already do.

Additionally, I believe this will throw an error if you have any pending packets to be sent over USB, won't it?

[tcr]

@johnnyman727 controller.closeTesselConnections will not be called with Tessels that don't identify themselves, i.e. a Tessel while booting does not wind up in the list of Tessels that are closed. How do we deal with that?

As for your second question, look at lib/usb_connection.js line 181 in my change. Essentially, given all transfers will timeout, it simply spin-waits until the last transfer is complete to resolve it. This is hacky, but reliable :)

[rwaldron]

@tcr need to run grunt tests and tooling locally

[johnnyman727]

Why did you need to remove this return?

[johnnyman727]

@tcr it works great on my machine! It reported when I had Tessels booting and they continue to work once they were up.

I added a few comments to clean up the code a bit before merging.

Thanks!

[Frijol]

Got this while working from your branch, is it from the branch itself or something else?

➜  ~  t2 wifi
INFO Looking for your Tessel...
WARN 1 Tessel device connected by USB may still be booting.
WARN No Authorized Tessels Found.
events.js:141
      throw er; // Unhandled 'error' event
            ^
Error: Connection was already closed...
    at USB.Connection._write (/Users/frijol/t2-cli/lib/usb_connection.js:70:14)
    at doWrite (_stream_writable.js:291:12)
    at clearBuffer (_stream_writable.js:401:7)
    at onwrite (_stream_writable.js:336:7)
    at OutEndpoint.WritableState.onwrite (_stream_writable.js:88:5)
    at Transfer.callback (/Users/frijol/t2-cli/node_modules/usb/usb.js:343:14)

[Frijol]

Also, getting false positives from this branch where it says "may still be booting" but really it's booted but I'm having USB issues. Not sure if we want to address this or assume USB should be working properly

[johnnyman727]

I also just had the case where it had definitely finished booting but then the CLI reported that it was still booting. This PR will need some thorough tests.

[johnnyman727]

Also related tessel/t2-firmware#119

[johnnyman727]

@tcr I've superceded this PR with #400. It takes some of the logic from this PR, some of the logic from #291 and some new logic to achieve the correct result. It also needs tessel/t2-firmware#118 merged.