LPC1769 USB-Connect necessary?

[lpcware]

Content originally posted in LPCWare by xpresso_1768 on Fri Nov 18 05:30:42 MST 2011
Hey,

i try to get the usbmem projekt to work. Now some questions about the necessary hardware setup. Does I need the USB-Connect pin or is a 1.5k pullup form D+ to 5V enough? Does I need the 33Ohm resistors connected in series?

Thanks in advance

[lpcware]

Content originally posted in LPCWare by xpresso_1768 on Mon Nov 21 02:31:43 MST 2011
Thank's Rob for the detailed reply! It contains everything I wanted to know.
And yes, I am using the lpc1769 module. Sometimes I am confused about all the different types and numbers... ;)

Thank's guys!
[U][/U]

[lpcware]

Content originally posted in LPCWare by Rob65 on Sun Nov 20 05:18:59 MST 2011

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Quote: xpresso_1768
I use the LPC1768 development board without anything else. The development board is bus powered and has a pullup for D+ to Vdd.

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Just to clarify: you are using an LPCXpresso 1769 module (with an lpc1768 chip :confused:) and you added your own USB connector and a pull up from D+ to Vdd (3.3V).
To power the board you connected the +5V of the USB connector to the Vin pin of the LPCXpresso module ?

That is enough to get your USB working - I use the same.

You are correct in assuming that the USB controller must be initialized (and your USB software stack must be running) before connecting.
Since connecting from the PC may take some time, it could be OK to do it this way. I have a number of boards that I use with just a pull up; as soon as I plug in the USB cable the software starts running and the USB controller is initialized in time for the PC to address the device.

Having a PNP transistor (as I did on my lpc1754 board) does have advantages:
While debugging your application you do not need to unplug/plug the USB cable each time, the LPCXpresso module will now unregister itself as soon as you press the restart button in the LPCXpresso's debugger - since this is very usefull while debugging an application with USB I am now adding the extra switch to all my boards.
Schematics of my lpc1754 board can be found at the bottom of this webpage.
Note that this also works for the lpc1768/9, it has the same USB controller and connections.

EDIT: Thanks to zero: there is a switch on the LPCXpresso board - so no need to add an external circuit, just the connector.
They should have added a USB mini AB conector - saves us a lot of fumbling around with connectors wach time ...

Rob

[lpcware]

Content originally posted in LPCWare by Ex-Zero on Sun Nov 20 04:56:17 MST 2011

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Quote:

I use the LPC1768 development board without anything else. The development board is bus powered and has a pullup for D+ to Vdd.

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:confused: That's wrong :eek:

As mentioned in link above, LPCXpresso1769 target board has everything you need except USB connector.
There's also a transistor included to switch 1.5k to D+ :eek:

See schematic (Page 6) of http://www.embeddedartists.com/sites/default/files/docs/schematics/LPCXpressoLPC1769revB.pdf

[lpcware]

Content originally posted in LPCWare by xpresso_1768 on Sun Nov 20 04:38:02 MST 2011
Oh no! I am taking about the xpresso base board with the lpc1768.
look here: http://ics.nxp.com/lpcxpresso/

[lpcware]

Content originally posted in LPCWare by Ex-Zero on Fri Nov 18 18:09:54 MST 2011
What is 'the LPC1768 development board' ?

Are we talking about mbed http://mbed.org/ ?

[lpcware]

Content originally posted in LPCWare by xpresso_1768 on Fri Nov 18 07:15:30 MST 2011
Thanks Zero, I allready read that! But it doesn't answered my questions...

I use the LPC1768 development board without anything else. The development board is bus powered and has a pullup for D+ to Vdd. On my opinion, I need a switch which connects the pullup with Vdd, because the usb controller has to be initialized befor I connect it to the bus.

[lpcware]

Content originally posted in LPCWare by Ex-Zero on Fri Nov 18 05:39:35 MST 2011

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Quote:

...necessary hardware...

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LPCXpresso1769 hardware or your own hardware?

Did you read this?

http://knowledgebase.nxp.com/showthread.php?t=2583