From: Tony Williams
Subject: Re: Best way to power array of LEDs?
Date: Fri, 06 Dec 2002 11:42:03 +0000 (GMT)
References: <email@example.com> <firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org> <email@example.com>
NNTP-Posting-Date: Fri, 6 Dec 2002 12:10:43 +0000 (UTC)
User-Agent: Pluto/1.14i (RISC-OS/3.60)
In article <firstname.lastname@example.org>,
Spehro Pefhany wrote:
> > In the original software, the sequence of "set port-
> > pins to logic 0, then set port-pins to outputs"
> > resulted in the pins being set to logic 1, the LED
> > lit up like a searchlight, with 130mA drawn off the 5v.
> Hmm.. so the voltage must have been high enough at
> the inputs to read as a "1", since most of the PIC
> inputs are TTL levels, it doesn't take much. I'll bet
> you wished you put a little transistor in there. ;-)
Abso-bleedin-lutely! But I had all those pins spare
on the PIC and a Real Cheapskate can never stand that.
> Must have been written as a series of BSFs.
No, and it still bit me Speff.
> > Fortunately that 20mA could be gated-Off for a few uS.
> > If that was done, then the original sequence worked
> > correctly.
> Hardware solutions work too. ;-)
Not on a finished board that is going out to the
customer, pdq. Any way, it was all academic, the
prototype worked ok, but the customer changed his
mind...... didn't even pay development costs. :-(
When he came back with yet another "thousands off"
development job he was politely told to P-off.