Main Site Documentation

+5 Volts when connected to USB


#1

I read in the docs that when connected to USB +5 volts is not available from the board (but 3.3v is available). If I am trying to use a shield which requires +5v with the Domino (and debug at the same time) is it kosher to connect both the USB and external power source - or will this cause problems?

Update; looks like (when connected to USB) I’m getting 3.3v from the 3.3v header connection and 4.6v from the 5v header connection. Makes sense if the incoming DC is going through a voltage regulator (or two).

Thanks!
Greg


#2

Yeh I was just about to say I tested mine and see 4.6-4.7 on the 5v header :slight_smile:


#3

That is incorrect, FEZ Domino gives you 3.3V and 5V both.

The 5V pin comes directly from the USB power, if you are powering from USB, so you will gee whatever your PC will provide.
Now, if you connect a power pack to FEZ Domino then you will get exactly 5V


#4

When connected to USB only I get +4.6v out of the +5v header pin on the Domino (just as brett reports). Interestingly an Arduino Duemilanove connected to the same computer (USB only) gives +5v on the same header pin.

So its ok to connect power to the “power input barrel connector” at the same time that I am connected to USB?

The particular shield that I am playing with uses 3.3v but does have one pull-up resistor connected to +5v. So if it is ok to connect power + USB (at the same time) then I can give that a try to see if that is the cause of my SPI comm issue with the shield.

Page 1 of the FEZ Domino brochure indicates that the +5v header pin only offers +5v when connected to an external power supply (and not just USB).

“5 Volts Out+”
"+ Available only with external power (not USB powered)."

So what I really want to know is if powering via external power while connected to to USB is kosher.

Thanks!
Greg


#5

“When connected to USB only I get +4.6v out of the +5v header pin on the Domino (just as brett reports). Interestingly an Arduino Duemilanove connected to the same computer (USB only) gives +5v on the same header pin.”

That is normal, FEZ Domino is a 72Mhz 32bit ARM processor and so it draws a lot more power so you will see a bit less than 5V

“So its ok to connect power to the “power input barrel connector” at the same time that I am connected to USB?”

Yes it is okay.

"The particular shield that I am playing with uses 3.3v but does have one pull-up resistor connected to +5v. So if it is ok to connect power + USB (at the same time) then I can give that a try to see if that is the cause of my SPI comm issue with the shield."
Yes it is okay, just connect it.
What shield are you using?

“Page 1 of the FEZ Domino brochure indicates that the +5v header pin only offers +5v when connected to an external power supply (and not just USB).”

We need to update the manual then.

"So what I really want to know is if powering via external power while connected to to USB is kosher."
Yes you are good to go :wink:


#6

Excellent! Thanks Chimpanzee!

What shield are you using?
A shield, offered by AsyncLabs, that contains an Atmel AT45DB161D data flash. And yeah I saw the sample for this piece but cannot open it due to the fact that it uses MF 3.0 which is not present on my machine. I’ll give the concurent USB+power connection a try and then maybe “port” the AT45DB161D sample so that it works for MF 4.0 only users.

I’m new to C#/VS but not programming. Figured a FEZ would be a fun way to aid in learning C# - plus it has some really cool features which need to be looked at :wink:

Thanks!
Greg


#7

Brochure is fixed


#8

Thanks! Did give external power + USB connection a try and all went well (the magic smoke was contained) - and I got a nice +5v out of the appropriate header pin (while being able to debug/etc. via USB).

Unfortunately this did not fix my SPI issue :frowning:

Greg


#9

What SPI issue?
You never mentioned what shield you are using. Maybe we already tried it and have code for it.


#10

What SPI issue?
You never mentioned what shield you are using. Maybe we already tried it and have code for it.

I did, a couple posts up in this thread :wink: Also queried on the SPI issue in a different thread.

Any way I got it working! Reading the dev id data via SPI seems to be working - at least I am getting back valid looking data. Interesting thing is that I am expecting 4 bytes return data but am getting 5. The first is always set to 255 but the following bytes match what I should be getting back!

Its nice to have a little success now and then :wink:

Thanks!
Greg


#11

Yes you did! I didn’t see it somehow!
So, you are trying to port uIP TCP/IP stack to C#? Or just trying to get the dataflash to work?

By the way, the project you couldn’t open because it is for 3.0 is still useful. You can still open the C# source code and copy it to your project.


#12

Starting easy :wink:

Just trying to get AsyncLab’s FlashShield 1.0 working with the Domino, well, to learn. The FlashShield contains a small “workspace”, the Atmel data flash mentioned above but no WiFi. We’ll look at WiFi later - as a more advanced project. This is just to get my feet wet :wink:

http://www.asynclabs.com/store?page=shop.product_details&flypage=flypage.tpl&product_id=28&category_id=6

Greg


#13

I never noticed the FlashShield before, now I see it.
Although using SD is better since you get file system…files… folders…etc, using dataflash can be a simpler option. Maybe I will order one myself and make a FEZ driver for it, using the old 3.0 project we have and with your help.

I will expose our management to this shield, maybe they will make a similar one for FEZ or stock the same one.


#14

Good news, can now read and write a byte to the buffer memory and figured out how to get rid of the extraneous byte that I previously mentioned. Owning this device is just a few hours of coding away :wink:

Yeah, I could use SD but several of the project ideas that I have for the Domino involve SPI so this is a good chance to learn! I do have a PIC based project (that uses SD) all breadboarded out - maybe will need to be re-jiggered for my next Domino :wink:

I know that it does not matter much to you… But I’d rather see you point customer’s at AsyncLab’s products (aint much margin in the FlashShield); they are great folks and I have been working with them for a while. Part of the reason that I want to see their shields working on the Domino is to increase value for both your and their customers.

The Arduino is what it is - but the Domino is Freakin Cool!

And just say the word and I’ll send you what I have - be gentle as I am a C# noob :wink:

Greg


#15

Maybe AsyncLab would like to stock FEZ Domino too. I believe someone here will contact them soon but if you like you can also contact them and recommend the FEZ.


#16

Will do :wink: