[Testannounce] Librem 5 Dogwood Update

Fri May 15 13:50:48 PDT 2020

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<h1>Librem 5 Dogwood Update</h1>
<p><b>Summary:</b><br> We are almost at the end of the Dogwood board
verification and have found and fixed a number of issues with the
initial Dogwood boards. We believe we will be able to complete testing
and start shipping Dogwood phones out within a few weeks. We have also
been working on Evergreen in parallel to procure the remaining
components we need for mass production.</p>
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<p>We know the community is eager to hear any updates we might have
about the Librem 5. Like with our <a
href="https://puri.sm/posts/librem-5-birch-shipping-update-delay-of-just-a-few-days/">Birch</a>
and <a
href="https://puri.sm/posts/librem-5-chestnut-hardware-changes/">Chestnut</a>
updates, we are trying our best to give you correct information for each
batch with a reasonable level of confidence without venturing into
speculation or guesses. This is especially important when it comes to
reporting hardware updates as it can take time and iterations to trace
down a problem into the component or mistake that caused it and often
first guesses for a root cause prove to be incorrect.</p>
<p>Like everyone else we have been impacted by the COVID-19 pandemic and
back in February we published an overall <a
href="https://puri.sm/posts/coronavirus-delays/">shipping update</a>
based on the best information we had at the time including dates for
Dogwood:</p>
<hr>
<ul>
<li>End of March: Librem 5 Dogwood internal hardware revision for the
Purism team</li>
<li>End of April: Librem 5 Dogwood batch for customer pre-orders</li>
</ul>
<hr>
<p><a href="https://social.librem.one/@purism/103968824971000879">We
started receiving the internal Dogwood hardware revision</a> a bit later
than expected in April and started the work to test and verify the
changes. As we mentioned in our <a
href="https://puri.sm/posts/breaking-ground/">Breaking Ground</a> post,
the Librem 5 is an entirely new phone built from the ground up and that
means significantly more testing and tweaking than with an off-the-shelf
design. Unlike with Birch and Chestnut batches, which only had minor
tweaks on the previous batch based on problems we uncovered during
testing, Dogwood represented a much larger change–a CPU flip to the
other side of the PCB to help with heat dissipation–that meant a full
redesign of the PCB layout.</p>
<figure>
<img
src="https://puri.sm/wp-content/uploads/2020/05/20200512_081030-1024x768.jpg"
alt="Dogwood PCB CPU side up">
<figcaption>Dogwood PCB CPU side up</figcaption>
</figure>
<p>We knew it would take longer to test Dogwood compared to Birch and
Chestnut and budgeted extra weeks for the tests assuming we didn’t come
across any major issues. Once testing was complete we would apply any
fixes and then send out the remaining Dogwood batch to customers. Like
with Birch and Chestnut we wanted to bring you along for the ride and
give you updates as we have them, but up until now there honestly hasn’t
been all that much to report except that the testing was in progress.
This kind of testing of every component in a long checklist is tedious
work and is only interrupted with a bit of excitement when something
doesn’t work as expected and you must drop everything to figure out why.</p>
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<h2>Dogwood Hardware Fixes</h2>
<p>It's been about a month since we started that verification and as
expected we did find some issues with the initial Dogwood boards.
Overall the glitches we found have been minor from a design and fix
perspective such as an incorrect MOS FET transistor part and a minor
mistake in the CPU power supply, but were glitches which resulted in odd
and sometimes much larger problems in the functionality of the device
ranging from damaging the USB section of the CPU in one case and
disabling an entire I2C bus in another! It’s taken more time than
expected to trace through these problems and then apply and test fixes
especially in the case of the CPU since it required reworks in the PCB
that were difficult to make on the existing boards and new CPUs.</p>
<figure>
<img
src="https://puri.sm/wp-content/uploads/2020/05/20200512_081019-1024x768.jpg"
alt="Dogwood PCB CPU side down">
<figcaption>Dogwood PCB CPU side down</figcaption>
</figure>
<p>Another system we have been looking into since Birch is GNSS (aka
GPS). GNSS is a pretty delicate thing, the GNSS satellite signals are so
weak, it’s like trying to spot an 80W light bulb in orbit (that’s about
the energy equivalent). What is received on the ground here on earth is
usually below the noise level of the antenna and takes pretty
significant signal processing to get data from it. This means that the
GNSS antenna signal path must be pretty close to perfect.</p>
<p>Besides this with Chestnut we discovered that ST Micro, the
manufacturer of the TESEO LIV3 GNSS multi constellation receiver we are
using in the L5, silently changed the recommendations for the antenna
input electronics design. Now in Dogwood we see that GNSS reception
still wasn’t great so we went back to suppliers and the drawing board,
applied some more changes and are now finally getting a fix!</p>
<p><p>Of course, <em>now</em> is the time to apply all of these fixes,
<em>before</em> we go into mass production. As you might expect, changes
are much more complicated with larger volumes, which is why we chose the
public small batch approach to begin with and invited you to come along
with us for this ride. At this point we have successfully verified
almost all of the components with only a handful left to go and we feel
we are pretty close to being able to greenlight the remaining Dogwood
PCB production within a week so we can start shipping a few weeks after
that. While this has been going on we have also been working in parallel
on Evergreen to complete procurement of the components we’ll need for
mass production.</p></p>
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<h2>What's Next</h2>
<p>Now that we are almost to the end of Dogwood hardware verification,
soon we will be able to shift focus from testing individual components
on a PCB to evaluating Dogwood and the CPU flip in particular as a
whole. We know many people are curious about the impact of the CPU flip
on heat dissipation and we intend to publish more detailed analysis soon
in a future update.</p>
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<p>Thanking you for your support,<br> — the Purism team <span>(feedback
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