--- In Kevin Cozens <> wrote:
For the TS7250, this is the case. The DIO are configured as inputs at hardware
initialisation. From the manual:
-- QUOTE
When the DIO pins are configured as outputs, they can "source" 4 mA or "sink" 8
mA and
have logic swings between GND and 3.3V. When configured as inputs, they have
standard TTL level thresholds and must not be driven below 0 Volts or above 3.3
Volts.
DIO lines DIO_0 thru DIO_3 have 4.7K Ohm "pull-up" resistors to 3.3V biasing
these
signals to a logic"1". The other DIO pins have 100K Ohm bias resistors biasing
these
inputs to a logic "1".
-- END QUOTE
So you could use a 'stronger' pull down than 4.7k if ouy are using DIO0 to 3,
or a weaker
pull down (47k?) on DIO4 to 7.
As he says, just because they show 3.3V when measured with a high impedance
voltmeter
doesn't mean they will be supplying significant current at this voltage level.
Hope this helps.
>
> evil666demonic wrote:
> > Is it possible that they are coming up as inputs, and that the voltage
> > we are seeing is really just from the internal pull-up resistors on
> > the DIO? This would explain why you read ~3.3V on those pins at
> > startup. Dangerous indeed if they attempt to source current,
> > especially in my case.
>
> It is possible. I have seen microcontrollers that come out of reset with the
> I/O pins set to input with weak pull-ups enabled.
>
> --
> Cheers!
>
> Kevin.
>
> http://www.ve3syb.ca/ |"What are we going to do today, Borg?"
> Owner of Elecraft K2 #2172 |"Same thing we always do, Pinkutus:
> | Try to assimilate the world!"
> #include <disclaimer/favourite> | -Pinkutus & the Borg
>
Yahoo! Groups Links
<*> To visit your group on the web, go to:
http://groups.yahoo.com/group/ts-7000/
<*> Your email settings:
Individual Email | Traditional
<*> To change settings online go to:
http://groups.yahoo.com/group/ts-7000/join
(Yahoo! ID required)
<*> To change settings via email:
<*> To unsubscribe from this group, send an email to:
<*> Your use of Yahoo! Groups is subject to:
http://docs.yahoo.com/info/terms/
|