Re: Mecrisp on the TI Stellaris Launchpad

From	Paul Rubin <no.email@nospam.invalid>
Newsgroups	comp.arch.embedded, comp.lang.forth
Subject	Re: Mecrisp on the TI Stellaris Launchpad
Date	2015-04-16 21:56 -0700
Organization	A noiseless patient Spider
Message-ID	<87h9sfwdy1.fsf@jester.gateway.pace.com> (permalink)
References	(1 earlier) <51cc1808-8727-4694-b94a-ee9d08209da4@googlegroups.com> <ec2dd465-48dc-49fa-8584-8fa1183ebbc8@googlegroups.com> <87618vyb8d.fsf@jester.gateway.pace.com> <mgpv33$469$1@dont-email.me> <mgq1j5$b0a$1@dont-email.me>

Cross-posted to 2 groups.

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rickman <gnuarm@gmail.com> writes:
> I was using a gadget to measure the voltage and current going into the
> rPi.  That side is at 5.25 volts give or take with around 400 mA of
> current.  I moved the meter to the launchpad and the output on the USB
> port is only 4.95 volts.

I remember reading somewhere (probably adafruit.com) that you should use
a pretty beefy 5V power supply with the rpi especially if it's under any
type of load.  They actually tweak their rpi power supplies to deliver
5.25 volts to compensate for some inevitable sag.

I don't remember hearing that the USB ports themselves are out of spec
but it's possible.  Despite popular misconception USB ports are only
supposed to be able to deliver 100 mA unless they grant the client
"permission" to draw more (up to 500ma), through a power negotiation
protocol that's part of USB.  Most x86 motherboards can deliver 500 mA
with no problem, so lots of badly designed client devices just assume
the power is available, and try to draw it without bothering with the
protocol.  Maybe something like that is going on here.

Thread

Mecrisp on the TI Stellaris Launchpad rickman <gnuarm@gmail.com> - 2015-04-02 21:08 -0400
  Re: Mecrisp on the TI Stellaris Launchpad rickman <gnuarm@gmail.com> - 2015-04-13 21:47 -0400
  Re: Mecrisp on the TI Stellaris Launchpad rickman <gnuarm@gmail.com> - 2015-04-16 23:37 -0400
    Re: Mecrisp on the TI Stellaris Launchpad Paul Rubin <no.email@nospam.invalid> - 2015-04-16 20:59 -0700
      Re: Mecrisp on the TI Stellaris Launchpad Mel Wilson <mwilson@the-wire.com> - 2015-04-17 13:16 +0000
    Re: Mecrisp on the TI Stellaris Launchpad rickman <gnuarm@gmail.com> - 2015-04-17 00:19 -0400
      Re: Mecrisp on the TI Stellaris Launchpad Paul Rubin <no.email@nospam.invalid> - 2015-04-16 21:56 -0700
        Re: Mecrisp on the TI Stellaris Launchpad rickman <gnuarm@gmail.com> - 2015-04-17 14:47 -0400
          WAS: Mecrisp on the TI Stellaris Launchpad  IS: Thunderbird Line Breaking rickman <gnuarm@gmail.com> - 2015-04-17 15:12 -0400
            Re: WAS: Mecrisp on the TI Stellaris Launchpad  IS: Thunderbird Line Breaking Martin Gregorie <martin@address-in-sig.invalid> - 2015-04-17 20:14 +0000
              Re: WAS: Mecrisp on the TI Stellaris Launchpad  IS: Thunderbird Line Breaking rickman <gnuarm@gmail.com> - 2015-04-17 16:59 -0400
            Re: WAS: Mecrisp on the TI Stellaris Launchpad  IS: Thunderbird Line Breaking David Brown <david.brown@hesbynett.no> - 2015-04-18 10:00 +0200
              Re: WAS: Mecrisp on the TI Stellaris Launchpad  IS: Thunderbird Line Breaking rickman <gnuarm@gmail.com> - 2015-04-18 09:32 -0400
                Re: WAS: Mecrisp on the TI Stellaris Launchpad  IS: Thunderbird Line Breaking Martin Gregorie <martin@address-in-sig.invalid> - 2015-04-18 15:15 +0000
                Re: WAS: Mecrisp on the TI Stellaris Launchpad  IS: Thunderbird Line Breaking rickman <gnuarm@gmail.com> - 2015-04-18 11:31 -0400
                Re: WAS: Mecrisp on the TI Stellaris Launchpad  IS: Thunderbird Line   Breaking Niklas Holsti <niklas.holsti@tidorum.invalid> - 2015-04-18 19:21 +0300
                Re: WAS: Mecrisp on the TI Stellaris Launchpad  IS: Thunderbird Line   Breaking rickman <gnuarm@gmail.com> - 2015-04-19 16:39 -0400
                Re: WAS: Mecrisp on the TI Stellaris Launchpad  IS: Thunderbird Line Breaking Alan Adams <alan@adamshome.org.uk> - 2015-04-18 18:52 +0100
                Re: WAS: Mecrisp on the TI Stellaris Launchpad  IS: Thunderbird Line Breaking "Rod Pemberton" <bork@lllljunkqwer.cpm> - 2015-04-18 18:55 -0400
                Re: WAS: Mecrisp on the TI Stellaris Launchpad  IS: Thunderbird Line Breaking The Natural Philosopher <tnp@invalid.invalid> - 2015-04-19 09:13 +0100
                Re: WAS: Mecrisp on the TI Stellaris Launchpad  IS: Thunderbird Line Breaking Dimiter_Popoff <dp@tgi-sci.com> - 2015-04-19 13:22 +0300
                Re: WAS: Mecrisp on the TI Stellaris Launchpad  IS: Thunderbird Line Breaking David Brown <david.brown@hesbynett.no> - 2015-04-19 22:09 +0200
          Re: Mecrisp on the TI Stellaris Launchpad mm0fmf <none@mailinator.com> - 2015-04-17 21:15 +0100
            Re: Mecrisp on the TI Stellaris Launchpad rickman <gnuarm@gmail.com> - 2015-04-17 17:02 -0400
              Re: Mecrisp on the TI Stellaris Launchpad mm0fmf <none@mailinator.com> - 2015-04-18 17:06 +0100
                Re: Mecrisp on the TI Stellaris Launchpad rickman <gnuarm@gmail.com> - 2015-04-19 16:57 -0400
                Re: Mecrisp on the TI Stellaris Launchpad Alan Adams <alan@adamshome.org.uk> - 2015-04-20 09:33 +0100
                Re: Mecrisp on the TI Stellaris Launchpad mm0fmf <none@mailinator.com> - 2015-04-20 18:03 +0100
                Re: Mecrisp on the TI Stellaris Launchpad rickman <gnuarm@gmail.com> - 2015-04-21 01:16 -0400
          Re: Mecrisp on the TI Stellaris Launchpad rickman <gnuarm@gmail.com> - 2015-04-17 20:20 -0400
            Re: Mecrisp on the TI Stellaris Launchpad Paul Rubin <no.email@nospam.invalid> - 2015-04-17 17:24 -0700
              Re: Mecrisp on the TI Stellaris Launchpad rickman <gnuarm@gmail.com> - 2015-04-17 20:40 -0400
                Re: Mecrisp on the TI Stellaris Launchpad Paul Rubin <no.email@nospam.invalid> - 2015-04-17 17:57 -0700
            Re: Mecrisp on the TI Stellaris Launchpad David Brown <david.brown@hesbynett.no> - 2015-04-18 10:04 +0200
            Re: Mecrisp on the TI Stellaris Launchpad Jan Coombs <Jan-54 <jenfhaomndgfwutc@murmic.plus.com>> - 2015-04-18 09:38 +0100
              Re: Mecrisp on the TI Stellaris Launchpad rickman <gnuarm@gmail.com> - 2015-04-18 11:04 -0400
                Re: Mecrisp on the TI Stellaris Launchpad David Brown <david.brown@hesbynett.no> - 2015-04-18 17:54 +0200
                Re: Mecrisp on the TI Stellaris Launchpad hal-usenet@ip-64-139-1-69.sjc.megapath.net (Hal Murray) - 2015-04-18 15:36 -0500
                Re: Mecrisp on the TI Stellaris Launchpad Theo Markettos <theom+news@chiark.greenend.org.uk> - 2015-04-23 07:59 +0100
                Re: Mecrisp on the TI Stellaris Launchpad rickman <gnuarm@gmail.com> - 2015-04-25 14:35 -0400
                Re: Mecrisp on the TI Stellaris Launchpad rickman <gnuarm@gmail.com> - 2015-04-25 15:44 -0400
                Re: Mecrisp on the TI Stellaris Launchpad rickman <gnuarm@gmail.com> - 2015-05-08 12:00 -0400
                Re: Mecrisp on the TI Stellaris Launchpad rickman <gnuarm@gmail.com> - 2015-05-10 03:36 -0400
                Re: Mecrisp on the TI Stellaris Launchpad Theo Markettos <theom+news@chiark.greenend.org.uk> - 2015-05-10 10:32 +0100
                Re: Mecrisp on the TI Stellaris Launchpad Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2015-05-10 12:56 +0300
                Re: Mecrisp on the TI Stellaris Launchpad rickman <gnuarm@gmail.com> - 2015-05-10 10:48 -0400
                Re: Mecrisp on the TI Stellaris Launchpad The Natural Philosopher <tnp@invalid.invalid> - 2015-05-10 16:05 +0100
                Re: Mecrisp on the TI Stellaris Launchpad Mark Wills <markwills1970@gmail.com> - 2015-05-10 08:55 -0700
                Re: Mecrisp on the TI Stellaris Launchpad rickman <gnuarm@gmail.com> - 2015-05-10 13:13 -0400
                Re: Mecrisp on the TI Stellaris Launchpad rickman <gnuarm@gmail.com> - 2015-05-10 15:34 -0400
                Re: Mecrisp on the TI Stellaris Launchpad albert@spenarnc.xs4all.nl (Albert van der Horst) - 2015-05-10 11:41 +0000
                Re: Mecrisp on the TI Stellaris Launchpad Theo Markettos <theom+news@chiark.greenend.org.uk> - 2015-05-10 16:56 +0100
                Re: Mecrisp on the TI Stellaris Launchpad rickman <gnuarm@gmail.com> - 2015-05-10 13:01 -0400
      Re: Mecrisp on the TI Stellaris Launchpad stephen@mpeforth.com (Stephen Pelc) - 2015-04-18 19:22 +0000
        Re: Mecrisp on the TI Stellaris Launchpad rickman <gnuarm@gmail.com> - 2015-04-19 17:04 -0400
          Re: Mecrisp on the TI Stellaris Launchpad Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2015-04-20 13:24 +0300
            Re: Mecrisp on the TI Stellaris Launchpad rickman <gnuarm@gmail.com> - 2015-04-22 13:23 -0400
              Re: Mecrisp on the TI Stellaris Launchpad Dimiter_Popoff <dp@tgi-sci.com> - 2015-04-22 20:44 +0300
                Re: Mecrisp on the TI Stellaris Launchpad rickman <gnuarm@gmail.com> - 2015-04-22 13:51 -0400
              Re: Mecrisp on the TI Stellaris Launchpad Waldek Hebisch <hebisch@math.uni.wroc.pl> - 2015-04-22 19:10 +0000
                Re: Mecrisp on the TI Stellaris Launchpad rickman <gnuarm@gmail.com> - 2015-04-22 15:31 -0400
                Re: Mecrisp on the TI Stellaris Launchpad Waldek Hebisch <hebisch@math.uni.wroc.pl> - 2015-04-23 02:08 +0000
                Re: Mecrisp on the TI Stellaris Launchpad Waldek Hebisch <hebisch@math.uni.wroc.pl> - 2015-04-24 02:52 +0000
                Re: Mecrisp on the TI Stellaris Launchpad rickman <gnuarm@gmail.com> - 2015-04-25 14:40 -0400
                Re: Mecrisp on the TI Stellaris Launchpad rickman <gnuarm@gmail.com> - 2015-04-25 15:42 -0400
    Re: Mecrisp on the TI Stellaris Launchpad albert@spenarnc.xs4all.nl (Albert van der Horst) - 2015-04-17 10:52 +0000
      Re: Mecrisp on the TI Stellaris Launchpad Dimiter_Popoff <dp@tgi-sci.com> - 2015-04-17 14:05 +0300
      Re: Mecrisp on the TI Stellaris Launchpad Paul Rubin <no.email@nospam.invalid> - 2015-04-17 07:56 -0700
        Re: Mecrisp on the TI Stellaris Launchpad David Brown <david.brown@hesbynett.no> - 2015-04-17 17:26 +0200
        Re: Mecrisp on the TI Stellaris Launchpad glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-04-17 17:01 +0000
    Re: Mecrisp on the TI Stellaris Launchpad Blajrs Jrolrsen <boegre@no.com> - 2015-04-17 13:36 +0000
      Re: Mecrisp on the TI Stellaris Launchpad anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-04-17 14:42 +0000
        Re: Mecrisp on the TI Stellaris Launchpad Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2015-04-18 00:25 +0200
          Re: Mecrisp on the TI Stellaris Launchpad rickman <gnuarm@gmail.com> - 2015-04-17 20:03 -0400
            Re: Mecrisp on the TI Stellaris Launchpad Paul Rubin <no.email@nospam.invalid> - 2015-04-17 17:14 -0700
              Re: Mecrisp on the TI Stellaris Launchpad rickman <gnuarm@gmail.com> - 2015-04-17 20:26 -0400
                Re: Mecrisp on the TI Stellaris Launchpad Paul Rubin <no.email@nospam.invalid> - 2015-04-17 17:32 -0700
                Re: Mecrisp on the TI Stellaris Launchpad rickman <gnuarm@gmail.com> - 2015-04-17 20:47 -0400
                Re: Mecrisp on the TI Stellaris Launchpad albert@spenarnc.xs4all.nl (Albert van der Horst) - 2015-04-18 08:47 +0000
                Re: Mecrisp on the TI Stellaris Launchpad rickman <gnuarm@gmail.com> - 2015-04-18 11:19 -0400
                Re: Mecrisp on the TI Stellaris Launchpad albert@spenarnc.xs4all.nl (Albert van der Horst) - 2015-04-18 15:52 +0000
                Re: Mecrisp on the TI Stellaris Launchpad rickman <gnuarm@gmail.com> - 2015-04-19 17:07 -0400
                Re: Mecrisp on the TI Stellaris Launchpad rickman <gnuarm@gmail.com> - 2015-06-09 03:04 -0400
            Re: Mecrisp on the TI Stellaris Launchpad Robert Wessel <robertwessel2@yahoo.com> - 2015-04-18 00:11 -0500
            Re: Mecrisp on the TI Stellaris Launchpad David Brown <david.brown@hesbynett.no> - 2015-04-18 10:32 +0200
              Re: Mecrisp on the TI Stellaris Launchpad rickman <gnuarm@gmail.com> - 2015-04-18 11:26 -0400
                Re: Mecrisp on the TI Stellaris Launchpad David Brown <david.brown@hesbynett.no> - 2015-04-18 17:57 +0200
                Re: Mecrisp on the TI Stellaris Launchpad Paul Rubin <no.email@nospam.invalid> - 2015-04-18 09:42 -0700
                Re: Mecrisp on the TI Stellaris Launchpad rickman <gnuarm@gmail.com> - 2015-04-19 17:11 -0400
            Re: Mecrisp on the TI Stellaris Launchpad Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2015-04-18 12:19 +0200
              Re: Mecrisp on the TI Stellaris Launchpad Dimiter_Popoff <dp@tgi-sci.com> - 2015-04-18 15:16 +0300
                Re: Mecrisp on the TI Stellaris Launchpad David Brown <david.brown@hesbynett.no> - 2015-04-18 19:57 +0200
                Re: Mecrisp on the TI Stellaris Launchpad Dimiter_Popoff <dp@tgi-sci.com> - 2015-04-18 23:11 +0300
                Re: Mecrisp on the TI Stellaris Launchpad David Brown <david.brown@hesbynett.no> - 2015-04-19 21:32 +0200
                Re: Mecrisp on the TI Stellaris Launchpad Dimiter_Popoff <dp@tgi-sci.com> - 2015-04-19 23:04 +0300
          Re: Mecrisp on the TI Stellaris Launchpad anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-04-18 09:15 +0000
            Re: Mecrisp on the TI Stellaris Launchpad David Brown <david.brown@hesbynett.no> - 2015-04-18 12:17 +0200
              Re: Mecrisp on the TI Stellaris Launchpad anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-04-18 13:08 +0000
                Re: Mecrisp on the TI Stellaris Launchpad David Brown <david.brown@hesbynett.no> - 2015-04-18 20:17 +0200
                Re: Mecrisp on the TI Stellaris Launchpad anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-04-20 15:33 +0000
      Re: Mecrisp on the TI Stellaris Launchpad rickman <gnuarm@gmail.com> - 2015-04-17 14:52 -0400
      Re: Mecrisp on the TI Stellaris Launchpad albert@spenarnc.xs4all.nl (Albert van der Horst) - 2015-04-17 20:06 +0000

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