Wow. So much has happened with this project since December 10
th. Many apologies for not posting an update sooner, but we've been quite busy.
The hardware design is nearing completion. We've made some changes that may or may not be temporary. I've
highlighted those changes here, and I'll include a bit of further discussion as to the
permanence of these changes at the bottom.
WiFi -
For now, we had to get rid of it. I'd mislabeled the module as being an
Infineon module, when in actuality it was a module that
incorporated the Marvell
Libertas chipset. For those that might not be aware, Marvell requires people implementing their products to sign an
NDA in order to access integration documents and driver source code. Their driver source is supposedly then provided under the
GPL, but they
apparently get a bit upset if you go and redistribute that code.
Hard Drive -The
HDD, despite its amazingly small form factor, had to go. I did some 3D modeling after the initial design phase to try and determine the best internal layout to keep the device as slim as possible. With the hard drive included, the device could not be kept slim. We're talking a device that literally looks like a brick here. Good news, though. I managed to locate some
NAND flash chips, and have integrated a 4gig
NAND chip into the design instead. In the near future (within a year or so) we will be able to integrate up to 16gigs per chip, and *I think* up to 4 chips per device. Using software RAID, this gives us an available 64gig
SSD. Right now the cost per GB is a bit too prohibitive to do that, but it's coming down quickly. Without the hard drive, the device is getting pretty slim :-D
LCD -If you haven't seen our
datasheet page, or checked out our contributors list, don't feel bad - 'cause I only just updated them. However, if you go check them now, you'll notice that we've switched our LCD to one that was donated by Lyle
Bainbridge. The screen he donated is the exact same screen as the one we were using before, with the addition of a rear
FPC that contains a few DC-to-DC converters. In English, that means that to 'drive' the LCD we don't have to power it with a ton of different weird voltages like we would have for the other screen. Instead we'll just be able to supply it with 3.3V for its logic, and ~30V for its
backlight. Since Lyle was also kind enough to supply us with a schematic he has tested, this donation has saved us *tons* of debugging time. We like not wasting time on things.
Thanks Lyle!I'm optimistic about all these changes, mainly because each change has had positive implications for our project (improved power consumption, lowered test/integration time, smaller form factor)
. It's possible that none of these changes will be
permanent, though.
Missing the
WiFi module means that in order to make use of a local broadband
internet connection, the connection has to be 'funneled' through the
Bluetooth stack, which has limited range. However,
WiFi and
Bluetooth coexistence is not something that is easy to produce in high-quality, and it requires a hardware-level cooperation between both RF controllers. I've considered switching to
NXP. They've got a
Wifi SiP in a
leadless package that coexists with their
Bluetooth SiP. Both chips are in stock at
Digikey. However, I can't seem to locate a good specification for their
WiFi SiP, meaning that I'll probably run into a similar situation as the one
Gumstix is in with Marvell. As soon as I have time to make the consideration on this, I'll be getting someone from
NXP on the phone to talk about it, though.
As for the
HDD, From a size and power perspective, I say good riddance! However, from a cost/gig perspective, I'm mourning its demise. This will eventually change, though, and I'm optimistic. For those people who might wish to build a phone with the
HDD integrated, I've still got an old design revision which includes it. If there's a want for it, it shouldn't be much trouble to bring it up to speed with the current schematic, and post it on the site as well. However, with everything that's going on right now I can't make any immediate promises about a layout for it -- good chance to get your name on the list of contributors, though!
As for the LCD, I have mixed feelings. On one hand, I love the new one. It's perfect in every way. On the other hand, this past summer I literally spent 2-3 evenings per week over a 6 month period trying to locate a supplier that sold it online to individuals in single quantities. I couldn't. Lyle was able to obtain a single unit through some professional contacts he had. That's great for him -- and us -- but I know that the average hobbyist doesn't have this kind of professional network set up. If this initial prototype goes well and I can drum up enough interest out on the
interweb, I'm willing to go through another search for a distributor, and I believe Lyle is willing to help. If a single-quantity distributor can't be found, we can consider group buys, or just switch to a different screen at that time. Either way - this is the screen I'd originally
spec'd for this project, and being that I have one in my hands, I can't pass up the opportunity to see the true potential of this device.
That's all for now folks. I have tons more to say, a schematic to publish, and tons of design notes to get up on the site. Keep watching the wiki and this blog for updates, as I'm sure it's going to be tons more busy here in the next few weeks.
Take care!
