Author Archives: Dave

Motorola’s USB charging scheme

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As I mentioned in the previous post, I have a Motorola Xyboard 8.2 Android tablet [1].

Motorola Xyboard 8.2 (Xoom 2 ME) Android tablet

Motorola Xyboard 8.2 (Xoom 2 ME) Android tablet

Among other things, I use it as a GPS (with live Google Maps) in the car – it’s a WiFi-only tablet, but I tether it to my phone via WiFi or Bluetooth, so the tablet can talk to Google in the car. This works great.

But after a day of driving, the tablet always runs out of power, even though I had it plugged into a car charger the whole time.

I tried a bunch of different car chargers, including ones rated for tablets and iPads, claiming to source anywhere up to 3.1 amps, but they all did the same thing.

Finally, I hooked up the USB charging port to some meters and an oscilloscope to see what is going on.

About USB charging

USB charging is an unreasonably complex subject. You can read lots about the details here and here and here (and of course here), but I’ll summarize:

  • Per the USB 2.0 spec, all USB devices can draw 100 mA (at 5v) without negotiation.
  • Also per the spec, USB devices can draw up to 500 mA (again at 5v) after negotiating with the USB host

In practice, lots of devices draw 500 mA without negotiating. They get away with it because most PC USB ports just supply 500 mA to all the ports, regardless of whether or not the device negotiates.

Smartphones usually want more, and tablets, much more. My Nexus 4 draws up to about 750 mA when charging. And the Xyboard tablet can draw up to 1.5 A. Most phones and tablets are smart enough to reduce the amount of current they draw if the USB port can’t supply what they want – the result is they charge slower. In the case of my Xyboard tablet, 500 mA isn’t enough to keep it from discharging – it just drains the battery slower. That’s why I run out of power after a day of driving.

It would be expensive for vendors to make a dumb charger that’s smart enough to do the USB power negotiation, and even if they did, 500 mA isn’t really enough. So they came up with their own schemes:

  • Apple has a complicated and slightly-secret scheme where on their dumb chargers they put resistors on the D+ and D- USB data lines. The effect of the resistors is to put different voltages on these lines, which indicate to the device how much current the charger can supply.
  • In 2007, the Chinese set a standard that if the D+ and D- lines are shorted together, that indicates that the charger can supply more than 500 mA (at least 1000 mA; often more).
  • In 2009, the EU set a standard almost identical to the Chinese one, except they say to put 200 ohms between D+ and D-. Happily, this is close enough to the Chinese standard that they work with each other.

So as of 2013 (as I write this), virtually all non-Apple high-current chargers do the Chinese thing and short D+ to D- to indicate their capability.

But the result of this mess is that Apple chargers can’t charge Android devices (very fast), and vice-versa.

What Motorola does

But that still doesn’t explain why I couldn’t charge the Xyboard (well enough to keep it from draining), even with a high-current Android-type car charger.

It turns out that, at least on the Xyboard 8.2/Xoom 2 ME (and possibly on other Motorola devices), they don’t follow either standard.

I started by looking at the various car chargers I’d been trying. Some were Apple type, some were Android type. I even put power resistors on the output and measured how much current they could supply without the voltage dropping – lots (2.6 to 3.1 amps, depending on which charger).

But none would charge the Xyboard at faster than 640 mA.

Motorola uses their own scheme. When you plug in the USB charging cable, it gradually loads the charger over a period of about 2 seconds. If you watch the voltage on an oscilloscope, you can see it gradually dropping as the tablet pulls more current.

If at the full current draw of about 1.5 amps the voltage drops below about 5.3 volts, then the tablet decides the charger can’t supply that much, and drops the charge rate to about 640 mA. (The threshold was somewhere between 5.28 and 5.33 volts when I tested.)

Since USB ports are supposed to supply 5 volts DC, +/- 5%, 5.3 volts is slightly more than the maximum 5.25 volts allowed. So any conformant USB charger will be interpreted by the tablet as “low current”, even if D+ is shorted to D-, and no matter how much current it can actually supply.

I’m guessing only Motorola’s own chargers supply 5.3+ volts.

It’s a shame that Motorola’s devices can’t charge from standard Android-type USB chargers. I have one of the Motorola car chargers on order; I hope that works.

And I hope this info is useful to somebody.

[1] I’ve tried 7″ and 10.1″ tablets, and I really think the 8.2″ size is the sweet spot, at least for me.

I like the Xyboard 8.2 – Motorola priced it way too high so it didn’t sell.

As it ought to be for the price they asked, it’s very well built (they claim it’s waterproof), and the ICS implementation is good (except for the minor Bluetooth problem I mentioned in my last post). It’s getting old now – if you can find one at a cheap price, it’s a nice unit.

But be aware that it’s orphaned – ICS is the last version of Android you can put on it; it sold so few units that there aren’t any custom ROMs available (although you can root it). It’s called the “Xoom 2 ME” outside of North America.

Pairing a Bluetooth keyboard with a Motorola Xyboard (Xoom 2) tablet

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I bought this rather nice Bluetooth keyboard for use with my Motorola Xyboard (Xoom 2) tablet.

BT_keyboard_IMG_6561

It was about $18, shipped, on eBay. It’s small, designed for Android (it has Android-specific keys instead of iPad keys), and runs on two AAA batteries, so I don’t have to worry about keeping it charged. (It uses about 2 mA – I measured – so should be good for about 500 hours of run time on a fresh set of alkaline AAAs.)

Unfortunately, I had trouble pairing it. I don’t think it’s the keyboard’s fault, since it paired perfectly with my Nexus 4.

After much fiddling, I got it to pair – here’s the trick:

  1. Before pairing, make sure the tablet does not already know about the keyboard. (That will happen if you had a previous unsuccessful attempt at pairing.) To clear the keyboard from the tablet, do a “scan for devices” on the tablet, with the keyboard powered off.
  2. In Settings>Input, select “SwiftKey Tablet X”.
  3. Then pair.

Then it works. At least it did for me, on Motorola’s stock Android 4.0.4 build for the Xyboard 8.2 (Xoom 2 ME).  I’d guess this might apply to other Motorola tablets, too.

I think this is Motorola’s fault, but given that this is an “orphan” tablet at this point, I don’t think they’re going to fix it.

My God, it’s full of… disk drives!

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What’s going on with the X-37B?

X-37B (USAF photo)

I read today that the USAF has launched one again, on, I think, the 3rd flight.

What is unique about this vehicle compared to most other space systems is:

  • It’s reusable and returns to Earth (lands on a runway, ala the Space Shuttle)
  • It has a long on-orbit dwell time (270 days was supposedly the spec, with the second flight lasting 469 days)
  • Some significant amount of on-orbit delta-v for orbital maneuvering
  • Payload capacity “similar to a pick-up truck”

What is this thing for? The government has been strangely silent about its purpose, leading to a lot of random speculation, none of which makes any sense to me. The only thing they’ve said is:

“The X-37B is a risk reduction vehicle for space experimentation and to explore concepts of operation for a long duration, reusable space vehicle.”

I’m sure that’s true to some extent, but I’m sure that’s not all that is going on; otherwise why all the hush-hush?

Some of the theories I’ve seen claim that it’s:

  1. For spying on the Chinese manned space program
  2. For spying on random spacecraft in orbit
  3. Some sort of on-orbit anti-satellite weapon
  4. For repairing satellites in orbit
  5. A ground-attack (or ICBM interception) weapon (rods-from-god or similar)
  6. An orbital bomber
  7. For stealing satellites, like in You Only Live Twice
  8. Some professor at the Naval War College said “the Air Force has always wanted a crewed space plane, and this was the closest they could get”.

None of those make sense. One at a time:

1 and 2 – Spying on other spacecraft

The DoD is already pretty good at pointing ground telescopes at spacecraft in orbit. Remember they offered to check out Space Shuttle Columbia’s missing tiles back in 2003? Matching orbits and a close approach to an opponent’s spacecraft would be tremendously provocative (it’s not as if you can do it secretly), and how much more can you really learn by looking at a spacecraft up-close vs. from a distance anyway? Not enough to justify this doubtless hugely expensive program, I’m sure. If despite that, you really want to do this, you don’t need a vehicle that can land. As for spying on the Chinese manned space program, why would that be of any interest at all? (Besides, it’s been in the wrong orbit for that.)

So I don’t buy those explanations.

3 – It’s an ASAT weapon

So why does an ASAT weapon need to land? No matter how much the thing costs, it’s got to be cheaper to just build and launch a new one every so often than land it, refurbish it, and re-fly it.

4 – Repairing satellites in orbit

That’s crazy. Maybe if it were manned; if that’s what you want to do it’d be way cheaper to fly repair techs on a SpaceX Dragon. And what possible purpose would there be in having the repair-bot sit on orbit for a year, or have the capability to land?

5 – Rods from God

Again, no need for such a thing to land. If you really want to build that, sure build it, but why complicate things by having it land? Makes no sense.

6 – Orbital bomber

First, that would violate the Outer Space Treaty. I can see people wanting to get out of that treaty, but I think the US would do so explicitly rather than in this not-very-sneaky way. But, again, why does it need to land? Maybe you can make a case that the USAF doesn’t want to leave nukes on orbit forever – they want a way to get them back eventually. But there are many simpler ways to accomplish that – it can de-orbit the warhead with a parachute (ala Corona, as well as the whole Apollo program), they could plan on a future OTV or manned spacecraft to collect warheads in 15 years, etc. Plus, who needs another way to deliver nukes anyway? The Soviets are not coming back, and the Chinese only want to sell us stuff.

7 – Pac-Man (waka waka)

Snatching someone else’s satellite out of orbit would be an act of war. And difficult, because you don’t know where it’s CG is or how much damage it’ll take by being bounced around on re-entry. And why do you need your snatch machine to sit on orbit for a year? You can always just launch it when you need it.

8 – Manned spacecraft wannabe

Except they already built the full-size version (that flying pink elephant, the Space Shuttle), and this one doesn’t carry anybody. And a Dragon will be way cheaper, and NASA is already funding that. Not to mention Orion (oops… too late, I mentioned it. It’ll probably never fly anyway.) And, of course, they’ll have trouble getting even one brave soul to sit in a space the size of a pickup truck bed for a year (let alone finding room for oxygen, water, and food for that duration).

So what’s it for, then?

OK, here’s my theory. It’s a spy satellite full of disk drives.

The payload bay has some sensors, probably high-resolution cameras; maybe other things too. The rest of the payload is disk drives.

The X-37B collects data (pictures, maybe sigint, maybe other things), and stores it on the disk drives. Every so often it changes orbits in order to be able to look at some particular thing at particular times (or just to keep the other guy guessing). Once the disk drives are full (a year or so), or sooner if the data is needed on the ground sooner, it lands.

It lands so that the data on the disk drives can be read off.

Why not just radio the data down? Because there is way, way, too much of it.

Suppose the payload bay is 4 x 8 x 3 meters (roughly a full-size pickup truck bed). That’s 96 cubic meters (96 million cc). A 3.5″ hard drive is 101.6 x 25.4 x 146 millimeters, that’s 377 cc. So there’s enough room for about 250,000 drives. Figure a tenth of that after allowing room for the sensors, power supplies, and cooling (cooling is a big deal in space). 25,000 drives at 3 TBytes each is 73 petabytes. (BTW, that’s about $2.5M worth of disk drives; peanuts for the DoD.)

73 petabytes over a year is 25 gigabits/second. That’s 24×7, including when not over a convenient ground station.

How does that compare with the bandwidth available for a satellite downlink? I don’t know exactly, but the whole X-band is only 500 MHz, as is the Ku band. The Ka band is 2.5 GHz. That’s the whole band. You do the numbers.

[Edit, March 2013: There’s a mistake in the numbers above – a pickup bed is about 4 x 8 x 3 feet, not meters. But on further thought the X-37B is almost certainly using SSDs instead of rotating media, and the density of that is a lot higher. So I think the two mistakes roughly cancel out, without changing the conclusion.]

What can you do with that?

The Earth’s surface area is 510 million square kilometers (about a third of that is land). Let’s assume 24 bits/pixel (you can divide that up into bands as you like). Unless I made a mistake in the math, 73 petabytes is enough for pixels 40 centimeters on a side, of the whole planet.

Or, somewhat bigger pixels, but multiple copies in the disk drives, so hardware on-board the spacecraft can compare old images against new ones, and identify differences. You get the idea.

Makes Google Earth look kinda…lame.

[Disclaimer: This is just a guess; I have no inside info. Just imagination and a calculator.]

How to add the “sent” label to GMail messages

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…or, how to “move” GMail messages to the “sent” folder. (GMail uses labels, not folders, but if you use 1 label/message you can emulate folders.)

This is my last posting about GMail for a while (I hope!). 5 posts down, you can see that I completely revised my July 20 posting about migration to GMail – it’s finally done.

GMail’s web interface won’t let you move messages into the “sent” folder, but you can do it if you sync your account with Outlook, then do it in Outlook:

  1. Install Google Apps Sync for Microsoft Outlook®.
  2. Install Outlook (I used Outlook 2003).
  3. Synchronize Outlook with the GMail account (this may take a long time – days – if you have a lot of mail)
  4. Move the messages in Outlook.
  5. Let it sync again.

That’s it. Now you can get rid of Outlook if you want.

How to remove un-labelled mail from GMail

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I had over 80,000 un-labelled messages (6.8 GBytes) in GMail. I wanted to delete them.

Guess what – there’s no way to select messages without any labels. Google’s own help files say “There isn’t a search operator for unlabeled messages“.

It seems I’m not the only one with this problem. After a Google search on the problem, I discovered that the only known method is to search using the “-label: ” operator that finds messages that don’t have a given label. If you have 4 labels you can search on messages that don’t have any of the 4 like this:

-label:Label1 -label:Label2 -label:Label3 -label:Label4

or

-label:{Inbox Outbox label1 Label2 …} // only for single-word labels

Which is fine if you only have four labels. I had hundreds of labels.

Google support said there was no way to delete just the unlabeled ones, except by hand.

But there is.

  1. Install Google Apps Sync for Microsoft Outlook®.
  2. Install Outlook (I used Outlook 2003).
  3. Synchronize Outlook with the GMail account (this may take a long time – days – if you have a lot of mail)
  4. Exit Outlook (important!)
  5. Go into GMail, select “All Mail”, click on “Select all messages that match this search”.
  6. Delete all the mail in the GMail account.
  7. Run Google Apps Migration for Microsoft Outlook® (this gets installed automatically when you install Apps Sync)
  8. Migrate your Outlook .PST file (the account you synced in step 3) to your GMail account.
  9. Restart Outlook. Let it sync with GMail (may take a long time – it’ll transfer the entire account).

You’re done. You can un-install Outlook now if you don’t want to use it (you don’t have to; it’ll stay synced with GMail).

I did this. It works. Now I have only the 792 messages that actually have labels.

Dropbox is still better than Google Drive

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[Update 2014: This is obsolete. Google Keep solves the problem better now.]

In July I switched from an iPhone to a Galaxy Nexus running Android Jellybean.

I was fed up with Apple’s sue-happy arrogance and with being locked to AT&T (I travel; AT&T’s international roaming rates are highway robbery).

Plus Jellybean just looked like a more advanced platform. Google’s price of $350 unlocked and usable anywhere in the world was a great deal. When Apple got an injunction against the Galaxy Nexus, I pulled the trigger and snapped one up before it got yanked off the market.

Back in 2009 I went thru a painful transition from the Palm Treo to the iPhone. One of the big issues then was getting my memos onto the iPhone in a form that was:

  • Synchronized with the PC (so I can edit on either device)
  • Reasonably secure (encrypted sync)
  • Editable offline (on either the PC or the phone)

My solution was to store memos in the “notes” field of address book entries. This synced securely with Google Contacts and I could edit my memos offline. It worked great.

Unfortunately the Android version of Google Contacts has a limitation on the size of the “notes” field. Neither the iPhone or the web version of Google Contacts have this problem, but I had plenty of memos that were too long to read on Android.

So I decided to move the memos into Google Drive (ex-Google Docs) files, thinking I could edit those on the phone or PC.

It turns out you can’t edit Google Drive documents when you’re offline. Also, the Google editor is complex enough to take an annoyingly long time to start on the phone (when I just want to check my shopping list).

But Dropbox works great:

  • Store the memos in Dropbox as plain text.
  • Put a shortcut to the memos folder on your “links” toolbar in Windows
  • Put the Dropbox widget (direct link to the memos folder) in the Android dock
  • Mark the memo files with a star (“favorite” them), so Dropbox will cache them locally in the phone for offline access.

That’s it. You can edit either on the PC or phone, and it syncs securely. It’s even smart enough to create a “conflict” copy if you make conflicting changes on the PC and phone.

I’m disappointed with Google Drive – this should be easy. And I don’t see why they put the size limit on Android address book notes (when there isn’t one on the PC or iPhone).

I’ll say this – the transition to Android was easy; nothing like the nightmare moving to the iPhone.

I think Apple has started a long, slow descent into irrelevance. They must think so too – winners compete, losers sue.

Questions are more valuable than answers

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…at least if you’re Google.

The interesting site Terms of Service; Didn’t Read gives Google a thumbs-down because “Google can use your content for all their existing and future services”.

I don’t think a thumbs-down is really fair here – I mean, that’s the whole point of Google.

Google is a service that gives out free answers in exchange for valuable questions.

Answers are worthless to Google (though not to you) because Google already knows those answers. But it doesn’t know your questions. So the questions are valuable (to Google, not to you). Because Google learns something from every question.

When you start typing a search into Google and it suggests searches based on what other people have searched for, that’s using your private information (your search history) to help other people. They’re not giving away any of your personal information (nobody but Google knows what you searched for or when), but they are using your information.

Google gets lots of useful information from the questions that people ask it. It uses that information to offer valuable services (like search suggestions) to other people (and to you), that they make money from (mostly by selling advertising).

That’s not a bad thing. It’s the only way to do many of the amazing, useful, and free things that Google does. I’m perfectly fine with it, but you have to more-or-less trust Google to stick to their promise to keep your private info private.

I think Google does a lot more of this than most people suspect.

When you’re driving and using Google Map to navigate, you’re getting free maps and directions. But Google is getting real-time data from you about how much traffic is on that road, and how fast it’s moving.

When you search for information on flu symptoms, Google learns something about flu trends in your area.

Sometimes I ask Google a question using voice recognition and it doesn’t understand. After a couple of tries, I type in the query.  I’ve just taught Google what I was saying – next time it’s much more likely to understand.

When you use GMail, Google learns about patterns of world commerce and communication, who is connected to who, who is awake at what time of day, etc. Even if it doesn’t read the contents of the mail.

When you search for a product, Google learns about demand in that market, by location and time of day and demographics (it knows a lot about you and your other interests).

Google learns from our questions – answers are the price Google pays for them.

Email migration from Eudora (or Thunderbird) to GMail

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Update November 17 2012: 

I started this post back on July 20 – four months ago – and have only finished the migration now. That’s because I found a lot of unexpected problems along the way.

The rest of this post is my new, improved, and corrected step-by-step guide on how to migrate email from Eudora (up to version 7) or Thunderbird to GMail, based on hard-won experience.

BACKGROUND

I’ve been using Eudora since 1995 (17 years). Before that I used Unix mail (Sun; early 1990s), CompuServe (back to 1981), and something called “The Source” (1979; I was ‘TCA818’). Disk space was expensive back then so I didn’t save a lot of email.

But since 1995 I’ve kept everything – disk drives got bigger faster than my mail archive. So I had about 14 GBytes of email in Eudora.

Eudora has been abandoned by Qualcomm since 2006 and is getting old; there’s a new open source version based on Thunderbird (“Eudora OSE”), which sucks.

As our company grows the job of administering Eudora users (plus myself) was getting too big for me, so I decided to outsource it to Google Apps for Business. Which means GMail, and migrating the old email.

ABBREVIATIONS

In the following, I’ll use these abbreviations:

  • E7 – Eudora 7 (or any earlier version of Eudora)
  • OSE – Eudora Open Source Edition (used only for migration)
  • Tbird – Mozilla Thunderbird
  • Outlook – Microsoft Outlook 2003 or later
  • OE – Outlook Express
THINGS THAT WON’T WORK

To save you time, here are some things that won’t work:

  1. Syncing E7 to GMail using IMAP
  2. Converting E7 to E-OSE, then sync E-OSE with GMail using IMAP
  3. Converting E7 to E-OSE, then sync Tbird with GMail using IMAP
  4. Converting E7 to Outlook Express, that to Outlook, then Outlook to GMail
  5. IMAPSize
  6. Importing E7 data with Outlook, then sycning to GMail
  7. Importing Tbird data with Outlook, then sycning to GMail
  8. Importing E7 data with Thunderbird
  9. Syncing Outlook with GMail via IMAP (use this instead; it works)

Trust me, don’t bother.

If you really care or don’t believe me, in the Appendix at the very end of this posting I’ve put some of my notes on why some of those don’t work.

(I haven’t the patience to describe all the problems…comments in the Python files give some more details.)

STUFF YOU WILL NEED

To do the migration, you’ll need the following:

These are only for the migration. Once it’s done you can throw away all of them.
Continue reading →

Slow-motion rocket videos shot with Nikon J1

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On July 7 I shot some video with the Nikon J1 of the joint CMASS/MMMSC launch at the Tuckahoe Turf Farm in South Berwick, ME.

After my generally scathing review of the camera (more for missed opportunity than anything else), I figured I’d give it a chance to show what it can do with high-speed photography – specifically, I wanted to try the 10 Mpixel 60 frames/second mode as well as the 400 and 1200 fps high-speed video modes.

Here is the result:

I put it together in Sony Vegas. The blurry clips were shot at 400 frames/second (240×640 pixels). The blurrier ones are at 1200 frames/second (120×320 pixels). The video is at 30 fps, giving 1/13.3x and 1/40x speed. This video shows the full resolution output by the camera.

(To be pedantic, playback is at 29.97003 Hz (that’s 30000/1001); from what I saw in Sony Vegas, the Nikon actually records at 399.6004 and 1198.8012 fps – which makes an odd sort of sense if you know NTSC.)

As you can see, all the video is lousy. It’s poorly exposed (despite some fixing in Vegas), heavily overcompressed (in-camera) and oversharpened (again, in-camera). The 1200 fps mode is worse than the already bad 400 fps mode. You can’t control it. I don’t blame Nikon too much – the high-speed Casio cameras seem to have similar problems. On the plus side, most of the video was shot at a shutter speed of 1/5000 second, which is neat to do. A couple clips were at 1/10,000th (!).

The video is good enough for some technical purposes, but it’s not a joy to look at.

Finally, you’ll note that none of the clips are at that fantastic, promised, 10 Mpixel resolution (60 Hz). It turns out that although the Nikon J1 will record stills that fast (for 1/2 second), you can’t control the shutter speed while it’s doing it. I didn’t know that until I got there and tried it. The shutter speed it picked (on a reasonably bright day) was so slow that each frame had lots of motion blur in it. So I didn’t bother. Just another needless firmware-based disappointment from the Nikon J1.

I’ve put the camera and lenses up for sale on eBay. Such a shame, Nikon. Oh well – I’m getting excited about the rumors of the new Canon mirrorless ILC system; maybe they’ll do better.