<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
</head>
<body>
<div class="main-wrapper">
<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>
</div>
<div class="grey-wrapper">
<div class="main-wrapper">
<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>
</div>
</div>
<div class="main-wrapper">
<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>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>
</div>
<div class="black-wrapper">
<div class="main-wrapper">
<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>
</div>
</div>
<footer class="align-center"> <img
src="https://puri.sm/wp-content/themes/wp-purism/images/brand.svg"
alt="Purism">
<p>Thanking you for your support,<br>
— the Purism team <span>(feedback at puri.sm)</span></p>
<hr>
<p>Note: contents of this email are CC-by-SA; feel free to forward
it to friends!</p>
<p><i>To remove yourself from our announcements list, simply email
<a href="mailto:announce-leave@announce.puri.sm">announce-leave@announce.puri.sm</a>
and you will automatically be instructed how to unsubscribe.</i></p>
</footer>
</body>
</html>