MBED IF+ and IF- Pins

15 Jun 2009

Hi, 

We are trying to connect the MBED to an embedded existing development platform.  We have allocated all the MBED pins except for the IF+ and IF-.  Are these for some sort of IrDA interface?

Thanks

Mike Beach

Hitex UK

 

15 Jun 2009

Hi Mike,

We are trying to connect the MBED to an embedded existing development platform.  We have allocated all the MBED pins except for the IF+ and IF-.  Are these for some sort of IrDA interface?

These are actually alternate USB connections for the mbed Interface (i.e. the mini-USB connector on the board). They were included so the interface USB connector could also be brought out on to a baseboard in the case where someone may want the connector in a different place.

For general operation, these can just be left unconnected.

If you do get it working, perhaps post a photo to the forum (it supports linking of photos and youtube); it'd be great to see what you're adapting!

Thanks,

Simon

15 Jun 2009

Hi Simon,

 

Thanks - this will allow us to route the USB connector through to the existing miniUSB connector on our baseboard.  We have already taken the Ethernet through.

Once we have the prototype up and running, I'll send some pictures.

Mike Beach

15 Jun 2009

Hi Mike,

The D+ and D- are the USB connections for the Target microcontroller USB, so may be the ones more suited to routing out on your basedboard.

The IF+ and IF- are for the mbed Interface itself, and we wouldn't really recommend breaking them out. The standard use model for using the mbed is to plug the USB cable in to the mbed itself (for programming and optionally power), and a USB connection external to the mbed is for the target USB device.

So we don't recommend using these IF+/- pins, especially as it could lead to people plugging in two cables to the same interface. We can't guarantee they will work, and they really are there as a future option to potentially allow use on custom boards that have restricted access (e.g. inside a prototype case).

For a baseboard (I assume your case), the programming interface should really be accessed by pluging a cable in to the min-B on the mbed Microcontroller board.

Hoep this helps!

Simon

16 Jun 2009

Hi Simon,

Our baseboard has a mini USB connector that is usually used for connecting to debug interfaces such as the FTDI FT2232. Here, we intend to connect the baseboard's miniUSB to the LPC2148 debug interface.  The CPU's own USB interface (i.e. the LPC2368) is connected to a second miniUSB connector on the baseboard's communications module.  From the point of view of mounting the baseboard in an enclosure, it is best to not connect anything directly to the MBED.

There will be links on the MBED carrier to make it difficult for users to connnect to both the MBED's own socket and the one on the baseboard.  I think we have links to allow almost every pin to be re-routed so it will be fun to set this up.

BTW: We are going to put a microSD card socket on the carrier as well.  Which MBED SPI port would you recommend we use so that the example programs will work?  Also, we have a row of holes to connect to the Nokia LCD mentioned on the website.  However I am told by our hardware guy that this is obsolete.  Is there an alternative display that people have used?

Thanks

 

Mike Beach

 

 

16 Jun 2009

Hi,

We are going to put a microSD card socket on the carrier as well.  Which MBED SPI port would you recommend we use so that the example programs will work?

You can choose whichever SPI port you like really; the code is very easy to change pinouts. But i'd recommend looking at the little breakout board Chris did, and using the same pins as that:

Also, we have a row of holes to connect to the Nokia LCD mentioned on the website.  However I am told by our hardware guy that this is obsolete.  Is there an alternative display that people have used?

As long as it is a SPI LCD, I think it'd be good to go for whatever is most available, and we can look at implementing a driver. We've used these nokia 130x130 clones (which tend to have various driver chips), and also a QVGA one which I got from Embedded Artists:

I don't know of any others in use yet. It'd be great to have a range of LCDs supported from a common base class, so please just tell us what one you end up choosing so we can get hold of some too.

Simon

21 Oct 2010 . Edited: 21 Oct 2010

Hi,

 

We're using the IF+ IF- pins in our design and I just wanted to mention that one should pull the IF+ pin to VCC with a 1.5K resistor.

 

Zainul.

28 Oct 2010

Hi Zainul,

Regarding LCDs, I found this link a while ago that may be of interest:

http://hackaday.com/2010/10/14/touring-the-available-nokia-lcd-screens/

Most of these look like they should work with mbed in much the same way (SPI port).

Andrew