Question on pull downs USB host with 1769

[lpcware]

Content originally posted in LPCWare by fariouche on Wed Nov 14 11:48:18 MST 2012
Hi,

I have a quick question: Can I have the 2 15k pull down resistors (necessary for Host mode) and still be able to use Device mode?

I would like to use the lpcxpresso 1769 in either Device or Host mode without having to use any jumpers to set the mode.

The lpcxpresso base board is using jumpers, thus my question.
If I keep them in device mode, the total pull down resitor will be 7.5K since the host also have them.

Thank you for your help

[lpcware]

Content originally posted in LPCWare by fariouche on Fri Nov 16 06:20:22 MST 2012
Ok, thank you for the answers! That's what I "feared".
I think I will end up using some transistors for that then

[lpcware]

Content originally posted in LPCWare by Tsuneo on Wed Nov 14 21:48:13 MST 2012
To switch between Host / Device, the external pull-down resistors have to be switched, like D+ pull-up resistor for Device.

An external OTG transceiver may be applied just to integrate these pull-up and pull-down resistors with switches into a chip.

"Fig 30 USB OTG port configuration" on the LPC1769 data sheet, ISP1302 is used for this purpose.
http://www.nxp.com/documents/data_sheet/LPC1769_68_67_66_65_64_63.pdf

You may apply any other OTG transceiver, like MIC2555, STOTG04E

Mic2555_vs_ISP1301 Connection Differences
http://www.lpcware.com/content/nxpfile/mic2555vsisp1301-connection-differences

Mic2555_vs_ISP1301 USB Transceiver Differences
http://www.lpcware.com/content/nxpfile/mic2555vsisp1301-usb-transceiver-differences

Tsuneo

[lpcware]

Content originally posted in LPCWare by daniel.widyanto on Wed Nov 14 21:07:44 MST 2012
You can't. For USB device it's PULL UP, not PULL DOWN (as in the USB host), that's required.