Re: [Gumstix-users] Problem with the Reset.

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We have had no reports of this on the verdex products.
Gordon

Toner, Ben wrote:
>
> I'm interested in a reset circuit too, and have tried a bit of 
> debugging...
>
> Looking at the PXA270 Reset requirements, the only two requirements I 
> can see is a pull down time of at least 6ms and absolute stability on 
> the power supplies, specifically VCC_BATT.
>
> As there is no access to the Verdex schematics, I can only assume that 
> the power supply schematic follows that of the example in the tps65022 
> datasheet.
> If that is the case then this problem could be down to noise on the 
> power lines? or TI have not correctly specified the connection to the 
> PXA270?
>
> There is some noise on the power lines, and this is expected in such a 
> design. 
> I can see it on the main supply input. 
>
> The tps65022, if implemented well, should clean most of that noise up 
> and I've had a quick look at the VCC_BATT line (at the tps65022 side) 
> and it seems stable with limited noise (50mv Pk-Pk).  It would be 
> interesting to see if there is any noise on it at the PXA270 side (on 
> the other side of the 4.7uF capacitor (if it is there?)).  I cannot 
> get to it and it is hard to trace without schematics. 
>
> Maybe that's something for Gordon to check?  Are there any signal 
> lines crossing the VCC_BATT connection on the PXA270 side of the 
> filtering capacitor that could induce noise?
>
> Assuming that is ok, it could be worth an email to TI to ask them if 
> the schematic example in their datasheet is proven to allow hard reset 
> to work?
>
> I'll try some more tests later in the week, but I don't want to go too 
> far and destroy my only Verdex..
>
> Ben
>
> -----Original Message-----
> From: gum...@li... on behalf of Gordon 
> Kruberg
> Sent: Tue 26/06/2007 15:49
> To: General mailing list for gumstix users.
> Subject: Re: [Gumstix-users] Problem with the Reset.
>
> We have an open ticket internally to resolve this issue, which was
> recently reported by another customer.
> We believe it has to do with how the gumstix handles nRESET in hardware.
> At this point, we can only suggest workarounds such as Dave H's
> cut-power or a gpio-triggered soft-reset.
> Gordon
>
> Sir Graham (EndoraSoft) wrote:
> > 
> > Hi,
> > 
> > We put a reset extern to Gumstix, but... not works well.
> > 
> > Sometimes the CPU is stopped but not reset..... (Not initialize the S.O)
> > 
> > This is the diagram:
> > 
> > 
> > Any idea about the problem......?
> > 
> > Any suggestion?
> > 
> > 
> > Regards,
> > Sir Graham
> > 
> > 
> > 
> > 
> >
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