Olimex LPC-2478-STK USB

Started by Mark April 16, 2010
Hi All

Just a word of warning to anyone developing USB on the Olimex LPC2478-STK.

There are two circuit diagrams on the Olimex web site:
- http://www.olimex.com/dev/images/ARM/LPC/LPC2478-STK-sch.gif
and
- http://www.olimex.com/dev/pdf/ARM/LPC/LPC-2478STK.pdf (the user's manual with a circuit diagram embedded in it)

The first shows the USB device connector connected to U2D+/U2D- and USB host to U1D+/U1D-.
The second shows the USB device connector connected to U1D+/U1D- and USB host to U2D+/U2D-.

Logically the device would be connected to U2 since this allows the host to run at the same time on U1 (the inversion is not true).

The Rev. A board (the one that I have and the one shown in the user's manual) has the USB device connected to U1D+/U1D-. Of course I was working with the first circuit diagram and - because things just didn't want to work - ended up tracing the tracks on the board, which resulted in the discovery of the cross-over and ultimately the second diagram...

What is also strange is that the USB_CONNECT and VBUS signals are not actually connected to USB_CONNECT or VBUS pins on the LPC2478 - even though the signals are names as one would expect. This means that these signals need to be be controlled via GPIOs instead.

Looking at the IAR USB code reference (I believe that the IAR board is an IAR badged Olimex board) it happily controls the USB_CONNECT pin, so I wonder how it manages to work...:-0

Regards

Mark
http://www.uTasker.com

An Engineer's Guide to the LPC2100 Series

Hi Mark,

This topic was discussed on the problem, too.
http://tech.groups.yahoo.com/group/lpc2000/message/45569

Tsuneo

--- In l..., "Mark" wrote:
>
> Hi All
>
> Just a word of warning to anyone developing USB on the Olimex LPC2478-STK.
>
> There are two circuit diagrams on the Olimex web site:
> - http://www.olimex.com/dev/images/ARM/LPC/LPC2478-STK-sch.gif
> and
> - http://www.olimex.com/dev/pdf/ARM/LPC/LPC-2478STK.pdf (the user's manual with a circuit diagram embedded in it)
>
> The first shows the USB device connector connected to U2D+/U2D- and USB host to U1D+/U1D-.
> The second shows the USB device connector connected to U1D+/U1D- and USB host to U2D+/U2D-.
>
> Logically the device would be connected to U2 since this allows the host to run at the same time on U1 (the inversion is not true).
>
> The Rev. A board (the one that I have and the one shown in the user's manual) has the USB device connected to U1D+/U1D-. Of course I was working with the first circuit diagram and - because things just didn't want to work - ended up tracing the tracks on the board, which resulted in the discovery of the cross-over and ultimately the second diagram...
>
> What is also strange is that the USB_CONNECT and VBUS signals are not actually connected to USB_CONNECT or VBUS pins on the LPC2478 - even though the signals are names as one would expect. This means that these signals need to be be controlled via GPIOs instead.
>
> Looking at the IAR USB code reference (I believe that the IAR board is an IAR badged Olimex board) it happily controls the USB_CONNECT pin, so I wonder how it manages to work...:-0
>
> Regards
>
> Mark
> http://www.uTasker.com
>

Hi Tsuneo

Thanks, that seems to tie up.

Strange thing is that I did a search for "LPC2478" - there were 355 threads which I checked through - only 2 of them were to do with USB but a different USB topic.

The one that you link to doesn't turn up, although it has LPC2478 in its subject - therefore I never found it before....

Regards

Mark

--- In l..., "t_chinzei" wrote:
>
> Hi Mark,
>
> This topic was discussed on the problem, too.
> http://tech.groups.yahoo.com/group/lpc2000/message/45569
>
> Tsuneo

Hi

As follow up I tried searching for the thread. Using advanced search I enter "LPC2478" in the subject and get 199 matches. Still this thread is not listed.
Then I tried with the search word "Olimex". This gave me 435 hits but again not including this thread.

After a little investigation I realised that the newest thread that I was getting (in both cases) was from around the 20th March 2009 (anything newer doesn't show)

How did you manage to find it again? Is this a general search problem or is it restricted to me???

Regards

Mark
--- In l..., "Mark" wrote:
>
> Hi Tsuneo
>
> Thanks, that seems to tie up.
>
> Strange thing is that I did a search for "LPC2478" - there were 355 threads which I checked through - only 2 of them were to do with USB but a different USB topic.
>
> The one that you link to doesn't turn up, although it has LPC2478 in its subject - therefore I never found it before....
>
> Regards
>
> Mark
>
> --- In l..., "t_chinzei" wrote:
> >
> > Hi Mark,
> >
> > This topic was discussed on the problem, too.
> > http://tech.groups.yahoo.com/group/lpc2000/message/45569
> >
> > Tsuneo
>

--- In l..., "Mark" wrote:

> How did you manage to find it again? Is this a general search problem or is it restricted to me???
>
> Regards
>
> Mark
>

The search feature for the Yahoo Groups is seriously broken. It used to work pretty well a couple of years ago. Lately, not so much.

Richard

On 17/04/2010 15:08, rtstofer wrote:
> --- In l..., "Mark" wrote:
>
>> How did you manage to find it again? Is this a general search problem or is it restricted to me???
>>
>> Regards
>>
>> Mark
>> The search feature for the Yahoo Groups is seriously broken. It used to work pretty well a couple of years ago. Lately, not so much.

The group is archived here:

http://www.embeddedrelated.com/groups.php

A search of the archive might work a lot better.

Leon
--
Leon Heller
G1HSM
Hi Leon

Yes, that works well!!!

Many thanks - this will certainly help in the future.

Regards

Mark
--- In l..., Leon Heller wrote:
>
> On 17/04/2010 15:08, rtstofer wrote:
> >
> >
> > --- In l..., "Mark" wrote:
> >
> >> How did you manage to find it again? Is this a general search problem or is it restricted to me???
> >>
> >> Regards
> >>
> >> Mark
> >>
> >
> > The search feature for the Yahoo Groups is seriously broken. It used to work pretty well a couple of years ago. Lately, not so much.
>
> The group is archived here:
>
> http://www.embeddedrelated.com/groups.php
>
> A search of the archive might work a lot better.
>
> Leon
> --
> Leon Heller
> G1HSM
>