RE: gEDA-user: Announcement : gTAG schematics released

[Stefan Petersen <spe@stacken.kth.se>]

Hello Luis,

On Mon, 5 Feb 2001, Luis Miguel Brugarolas wrote:

> 1.- I have used EZ-USB parts before the company was bought by Cypress.

Aha an experienced user user! Good! What is your over all experince of
these chips? Are they good or have you gone further to better stuff? A
couple of my friends are trying to use a Philips chip and a PIC.
Apparently the Philips chip are a bit buggy?


> In my first prototype I used the RESET arangement recommended by the
> manufacturer, which is the one used in gTAG. While this worked well
> for some PCs it did not for others 
[snip]
> We measured in those PCs (well known manufacturer) the USB supply rise
> time was very slow. You can fix for this PC but tomorrow will come
> another slower, and you have to change once again. We solved th
> problem using a 3-pin MAX-810SEUR-T connected to RESET, GND and +3.3V

Hmm, you're right. They usually suck, these cap-res stuff. I have a power
supply circuit from Maxim that converts 5V to 3.3V (MAX882). I looked at
the data sheet and it said it has a rise time of the power out of 200
us. Hope it's enough. So it seems like I'm saved by the bell :-)

Serious, I didn't consider this at first. When you pointed it out I
thougth "o, no", but after looking in the data sheet for the Maxim MAX882 
I think it will work as is.


> 2.- IMHO I2C bus should have an expansion port including SCL, GND,
> +3.3V and SDA.

Stephen already answered this and I let the case rest. Of course he's
upset by the extra connector I "sneaked" in. ;-)

Thanks for your input. I really appreciate it!

Regards,
/spe
/----------------------------------\
! Stefan Petersen, MSc EE         !  \    
! http://www.stacken.kth.se/~spe/ !    \_________________________
! spe@stacken.kth.se              !    /  ! umop apisdn 'sdoo !
! stefan.petersen@home.se         !  /    ---------------------
\----------------------------------/