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'[PIC:] Powering a QuickProto-01 from an external 5'
2005\10\02@120316 by Jan-Erik Soderholm

face picon face
Hi.
This is an variation on the other QuickProto/EasyProg thread... :-)

I'm using (at least planning to) the QuickProto for an
USB based prototype (using 18F2550).

Now, this applikation will probably be "bus-powered", that is,
taking the 5V from the USB connector.

So, is it safe to feed the QuickProto from an external 5V
source ? Or will it conflict with the internal PSU ?

The circuit doesn't use much (proc, xtal, a few caps, an USB-b
connector), so it could be built on a "strip-/vero-board", but
I thought it was a nice time to test a QuickProto... :-)

Jan-Erik.

PS:
Flashing the 18F2550 in the QP from the EP run OK.
It was just a clean build of the "mouse" demo as
supplied with the USB "kit" from Microchip...



2005\10\02@130532 by olin piclist

face picon face
Jan-Erik Soderholm wrote:
> So, is it safe to feed the QuickProto from an external 5V
> source ? Or will it conflict with the internal PSU ?

That's what jumper J3 is for.  Cut it and the on board power supply is
decoupled from the 5V supply line on the board.  The 11-30V and 5.5V supply
lines will now be dead unless you supply normal external power to the board.

> Flashing the 18F2550 in the QP from the EP run OK.

Thanks, that's good to know.  How did you end up connecting the two?


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com

2005\10\02@132523 by lm XA (TN/PAC)jan-erik.xa.soderholm

flavicon
Olin Lathrop wrote :

> Jan-Erik Soderholm wrote:
> > So, is it safe to feed the QuickProto from an external 5V
> > source ? Or will it conflict with the internal PSU ?
>
> That's what jumper J3 is for.  Cut it and the on board
> power supply is decoupled from the 5V supply line on
> the board.

OK, I see. It's currently a blank wire jumper, any special
reason it isn't a regular jumper like J5, J6, and J7 ?
I'll probably replace it with a two-pin heder and a jumper...

So, I'll just connect 5V from the USB connector to one of
the 5V rails in the proto-area then, right ?

> > Flashing the 18F2550 in the QP from the EP run OK.
>
> Thanks, that's good to know.  How did you end up connecting the two?

24 VDC to the normal power input of the EasyProg.
The two RJ sockets connected.
Serial input (actualy the same USB/ser adapter I use for the
Wisp628) connected to the seriel port of the EasyProg. The
adapter mates directly whith the EP, so there is no
RS232 cable...

I programmed the HEX file from the "mouse" demo from the
Mchip firmware framework (had to do a few changes since the
demo was written for the 40-pin 18F4550 and the specific
hardware found on the "PICDEM FS USB" board).

Jan-Erik.
>
>
> *****************************************************************
> Embed Inc, embedded system specialists in Littleton Massachusetts
> (978) 742-9014, http://www.embedinc.com
> --

2005\10\02@172706 by olin piclist

face picon face
Jan-Erik Söderholm wrote:
> OK, I see. It's currently a blank wire jumper, any special
> reason it isn't a regular jumper like J5, J6, and J7 ?
> I'll probably replace it with a two-pin heder and a jumper...

I had originally intended all the jumpers except J1 to be soldered wires
with J1 left as open pads.  This would be the normal configuration used most
of the time.  Soldered wire jumpers are more reliable and won't have
intermittent or noise problems, especially when in series with the power
supply.  The normal usage of this board wouldn't be to go back and forth
between configurations, so I figured someone would either leave the jumpers
alone or cut them once and leave them that way.  The manufacturer installed
jumper blocks for a few of these even though they were all listed the same
on the BOM.  Oh well.

> So, I'll just connect 5V from the USB connector to one of
> the 5V rails in the proto-area then, right ?

Yes, after J3 is cut.  And keep in mind that USB power is rather loosely
specified on the device end.  It could be just a little over 4V worst case
if I remember right.  The minimum guaranteed voltage is definitely below the
4.5V level which is the minimum required by some digital chips.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.co

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