Can we remove the USB disconnect circuit? about core

[satishgn]

USB disconnect circuit is crucial for the proper working of usb dfu & usb
serial thing. Removing this circuit is not an option. The firmware code use
this circuit to pull the usbd+ line so that the host pc is signaled to
reiterate the usb device.

On Jun 26, 2013 9:59 PM, "cazzo" [email protected] wrote:

Looking into whether the USB disconnect circuit is actually necessary, or
whether it can be removed without affecting the functionality of the Core.
Considering that the primary uses of the Core will be wireless, it would be
great to be able to get rid of these parts to save real estate that can be
used for some of the other parts we're trying to add.

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[zsup]

When in the usb-dfu and usb-serial processes does this step happen? Can it be emulated by unplugging the Core and plugging it back in?

I realize that's not a perfect solution, but given that once these are out in the field we're not expecting people to use USB very much, it might be a fair trade-off.

[satishgn]

Plugging/uplugging may not work on core because of usb timing constraints else we could have emulated if there was backup power for core.

[satishgn]

To add on what we require is delayed hardware enumeration after applying power & which is only possible with the disconect circuit.

[satishgn]

How about replacing the throughhole male header pins with the SMD ones. That will free one side of the board and since there are 2 rows that should give us good space. I was investigating this digikey part no.: A106611TR-ND

If this can be done than we can retain all the existing parts where footprint was an issue . Also going with the SMD part will also benefit in assembly as all the parts can be accomodated in Reflow soldering. I will create a separate issue no for this.

[zsup]

Closing this issue because it doesn't seem like this will be necessary

[andyw-lala]

Are there any DFM improvements that can be made ?
Zach, you were saying that that section of the board was problematic, or
did I misunderstand ?

On Thu, Jun 27, 2013 at 11:19 PM, cazzo [email protected] wrote:

Closing this issue because it doesn't seem like this will be necessary

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Reply to this email directly or view it on GitHubhttps://github.com//issues/10#issuecomment-20169672
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Andy

[zsup]

yes but we've got the other issue for increasing the spacing between 0603s, which was really the issue. So @satishgn do be sure to increase the spacing between the 0603s in the upper left corner of the board, in particular. the other troublesome parts were the LEDs and their resistors, which are all getting re-designed anyway (to the RGB and the resistor array)

Zach Supalla
312.953.3413

On Thursday, June 27, 2013 at 11:25 PM, andyw-lala wrote:

Are there any DFM improvements that can be made ?
Zach, you were saying that that section of the board was problematic, or
did I misunderstand ?

On Thu, Jun 27, 2013 at 11:19 PM, cazzo <[email protected] (mailto:[email protected])> wrote:

Closing this issue because it doesn't seem like this will be necessary

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Reply to this email directly or view it on GitHubhttps://github.com//issues/10#issuecomment-20169672
.

Andy

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[technobly]

@cazzo @satishgn you should be able to at least simplify the circuit down to 2 components like this one used on the mBed board http://mbed.org/media/uploads/chris/mbed-005.1.pdf

Cheap P-Channel FET
http://www.digikey.com/product-detail/en/BSS84/BSS84TR-ND/244213