Nov. 25th, 2018 01:48 pm

pyusbip

joshua0: (Default)

I spent this last Thanksgiving week at home with my family in the greater Boston area, which has been a wonderfully relaxing break from all the goings-on of my ordinary life in the Bay Area. Since I planned to get a little bit of work done for a client, I brought with me some development boards, including a Lattice MachXO3L eval kit. I had a productive Monday and Tuesday, getting quite a lot done, testing all the while in simulation, but by Friday, I was ready to test on hardware, and this posed a problem: the tool to program a bitstream onto the board runs on Windows and Linux, but I only had my Mac with me. I considered all the obvious solutions to this problem, weighed them each on their individual merits, and then discarded them all and chose the most complicated unreasonable approach possible.

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A few months ago, I wrote a little review of the Wahoo ELEMNT BOLT, and a miniature teardown of the software on it. I was surprised to find that it, in fact, ran Android, but that the license compliance story on it was not great. Over the intervening time, though, I've been exchanging some mail with Chip Hawkins, the CEO at Wahoo, and it sounds like they're working on getting the licensing story all fixed up there -- and, to my surprise, that engaging with the enthusiast community is something that they are interested in! So, this post has a short update on some of those discussions, and my experiments so far in modifying the thing.

My initial post led off with this arguably clickbait-like statement that the device was in violation of its myriad licenses, so I think it is only fair to the Wahoo team to give an update on where that stands. As of the time I write this, source isn't available for the GPL components, and attribution isn't in place for the Apache components, but as far as I can tell, Chip and his team are pretty serious about getting this squared away. They have a release pending that has been occupying basically all of their engineering time, which also will have some UI changes; so, for the attribution components, they plan to include those in the new UI, rather than running a fire-drill to retrofit that a branch that is unlikely to see another release again. This makes sense to me. My impression is that the next release will have attributions included, then, and kernel source for that release will go out with it, too. They seem to understand what components they need to release source for, and where to look for other licenses that they need to include. So, my claim is that anyone who wishes to be mad about there not being source available yet, should wait for the next release -- it does sound like they are trying, and have a plan to get into compliance! The Android app already has an attributions tab, which is a good start, and I hope that they get the on-device software squared away soon too.

Chip also gave me some information on doing some hacking on the device, which is exciting. They plan to release a recovery image (for Android people, this is a full update.zip, including boot, /system, and userdata images) along with the next release, but until that is ready, one caveat to all of the following is that would-be hackers must be extremely careful, because there is currently no image available to restore a device from unless you create one, and further, that if you modify the root filesystem, then the device will no longer be able to take over-the-air updates until you restore it from backup.

With all those warnings said, here are some tricks to get you started messing with the device. I mentioned in my previous post that the device had an ADB daemon running, but it wasn't accessible; as it turns out, there is a key shortcut to get access to it! If you press the power button and the up button on the right side at the same time, the ADB daemon should unlock. Chip notes that it's best to press them a few times in a row in order to ensure that the event actually happens; after you do that, unplug the device from your computer, then plug it back in, and you should be able to adb shell in. For me, the ADB daemon was already running as root, but if this wasn't the case for you, I am told that adb root should work.

Since there isn't a recovery image available yet, I recommend that the first thing that you do is to make your own. To get a bare minimum backup of the system image on your device, you might want to run something like for i in boot system recovery nvdata ; do adb pull /dev/block/platform/mtk-msdc.0/by-name/$i elemnt-backup-$i.img; done, which will grab a backup of, at least, everything you need to reflash a known-good bootable configuration onto your device.

Once you have boot and system partition images, you are now in a much safer position to explore the device. The other step that you might want to take is to unlock the bootloader on the device, so that you can flash those images again if you need to. The ELEMNT devices run Fastboot, but they have a very finicky version of Fastboot running on them; as far as I can tell, after every command, you need to unplug and plug the device back in, or else it will not respond to you again. Unlocking the bootloader will wipe any data that you have on the device, so make sure to back up anything that you want (either using ADB, or over MTP with Android File Transfer) before you do it!

To boot the device into Fastboot, turn it all the way off, then hold the "down" button on the right side while pressing the power button. If everything goes well, it will give you a black screen, and present a Fastboot interface over USB. Run fastboot oem unlock on your computer side; you'll get a message like "waiting for user" or something of that nature. When you do, press the power button once, and wait; you'll eventually get a message like "erasing user data...", and then the device will be unlocked. To be sure of that, you can unplug and plug the USB connection back in, and then run fastboot getvar all; in there, you'll see the message "unlocked: yes". When you're ready, you can then run fastboot continue, and your device will continue to boot. If you get yourself into trouble later, you can restore your backup with something like fastboot flash:raw boot elemnt-backup-boot.img, and similarly, fastboot flash system elemnt-backup-system.img.

I had been putting this post off for a while, since I had planned to try to modify the .apk that runs the thing. Sadly, I never really got time to do that. But I did get mail from Chip saying that he didn't have objections to people redistributing modified system ROMs -- and modified BoltApp.apks. So what I'm hearing is that, for the enterprising hacker with spare time, this could be a fun toy! He notes that the launcher is pretty careful about monitoring the main app for crashes, and that there are intents that you can send the launcher to make it happier; I tried decompiling the launcher, but found that the version of Android that runs on the device is not compatible with any of the de-odex tools that are out there. So that also sounds like future work.

Anyway, I'm still using mine. I still wish it would boot faster, and especially that it would restore a paused ride faster. I also wish that it would show me sunset times. But I've put a few hundred miles on mine by now, and it hasn't eaten a ride yet. And that makes it better than my Edge 510.

joshua0: (Default)

There have been a lot of exciting changes for me in the past month -- maybe the most exciting being that I left my job, and so I've been spending the last month biking and hiking and generally getting outside. I've been meaning to write about those, and I have a post drafted about that, but this is not that post. Instead, this post is an unrepentently nerdy dissection of a new toy that I got, in which I unintentionally buy yet another Android device -- a Wahoo ELEMNT BOLT, which is a bike computer with GPS (and other data) logging support, phone and internet connectivity, and a whole bunch of exciting gadget and doodad features.

Update August 6th, 2018: I am in contact with Chip, at Wahoo Fitness, about the licensing issues -- and with promising news about hackability! I'll write a little more later when I get a chance, but I figured this update should be front and center....

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joshua0: (Default)
MicHead board installed

(click for full writeup)

There is, truly, no kill like overkill. This is a story of how I spent untold tens of hours of engineering time designing and retrofitting an upgrade for the headphones amp that I keep at my desk to support a microphone input, and all for no real good reason. I jumped through contortions at every stage to get there. But, it was fun -- and that's what matters.

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