2020 Project Status? #13
Comments
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I am just completing the build of mine, I have some spare boards (unpopulated) available. I may have some spare components (eg the Skyworks switch) .. I'd like to at least get mine up and running first though. |
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It's a really cool project. I purchased a commercial AIS for my boat. But I think this could be both a great learning platform and a great open source project.
…-------- Original Message --------
On Apr 24, 2020, 7:30 PM, Robin Szemeti wrote:
I am just completing the build of mine, I have some spare boards (unpopulated) available. I may have some spare components (eg the Skyworks switch) .. I'd like to at least get mine up and running first though.
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i did not want to open an issue just to ask this one: but what does it cost to build one myself compared to getting a commercial unit? |
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The basic cost in components is around maybe €75 to 100 euros, but you will
have to buy some parts in x5 even though you only need x1 You also need
the PCB .. I was able to mix the PCB with others I was ordering so my price
was not too bad, I have some spare PCB now.
You will also need to order a stainless stencil for the solder paste. You
will have difficulty mounting some of the smaller IC without a stencil for
the paste. The radio transceiver chips are quite small to mount, and the
T/R switch is very small (2mm x 2mm, 12 connections) if you are not
experienced, it will be difficult for you.
I took quite some time to get the software to load and run. I forget what
the exact problem was, but it took a while to find it, I think it was in
the initial clock configuration. Allow "some time" to get the software
loaded if you are new to the STM32. Maybe a day or two ... maybe more,
depending on your experience level.
…On Sun, 26 Jul 2020 at 11:02, Bo Herrmannsen ***@***.***> wrote:
i did not want to open an issue just to ask this one: but what does it
cost to build one myself compared to getting a commercial unit?
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that is not so bad (price) and i do have experience with SMD and have the tools (dispenser and oven) |
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Are the hardware components list and schemas on OSH? |
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They are on GitHub ...
…On Sat, 29 Aug 2020 at 17:22, mfrostus ***@***.***> wrote:
Are the hardware components list and schemas on OSH?
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Hello all. I have suddenly found my self with spare time on my hands, and I'm thinking about reviving this project, or rather the evolved version of it. I built the next version of the circuit on my boat (including antenna) and it has been operating for 3 years now. I'd like to start a discussion about the best way to make it available. Here are some basic facts about it (sorry, all the internal photos of it were lost overboard with my iPhone!)
The design allows the transponder and antenna to be mounted as one piece somewhere up high, directly onto 1" railing, secured using UV-resistant heat shrink tubing (3 years and counting, still looks great). The 4-wire (phone) cable to the cabin travels inside the railing or mast, until it hits a control circuit where it's converted to USB for feeding into a RPi or some other similar device. I've had great success with 3.3V level UART travelling > 35 feet in twisted pair cable with no issues. I have often thought about commercializing this, but the amount of regulatory pain here in the US is higher than my threshold (I deal with the FCC as part of my day job). What if I made this available as a do-it-yourself kit? I think this would allow me to dodge the regulatory reef, but it comes with its own challenges. What would a system like this be worth? Let's discuss here. |
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A kit would be OK, but I think without the SMT stencil and the ability to
use a SMT oven, people will struggle. I still have some spare PCBs if
anyone wants one.
I had some success, my board runs, and I can load software to it that
appears to function, but I've never seen a successful transmission from it
.. I put it on one side. I found compiling as a non-HAL project to be
difficult, there are errors in the clock configuration in the project as it
stands, so it loads and then crashes. Debugging is dificult in this
condition. What I did notice is I could successfully use the STM32 cube
programmer to load and run test code perfectly, but the same not the
bootloader ... it took me some time to find the clock config problem.
A kit might be interesting, but I already have large amounts of SMD
components so just a board and some of the harder to find pieces would be
good for me, or I just add a board to my next PCB order. Either is good.
It would be nice to see it make progress again, apart from the one I built,
I am not sure how many others have built one. A kit may improve that
situation, but they will need excellent SMD skills.
…On Sat, 29 Aug 2020 at 18:01, Peter Antypas ***@***.***> wrote:
Hello all. I have suddenly found my self with spare time on my hands, and
I'm thinking about reviving this project, or rather the evolved version of
it.
I built the next version of the circuit on my boat (including antenna) and
it has been operating for 3 years now. I'd like to start a discussion about
the best way to make it available. Here are some basic facts about it
(sorry, all the internal photos of it were lost overboard with my iPhone!)
- 1" wide 4-layer PCBA directly attached via SMA connector to custom
"flowerpot" antenna, tuned to 162MHz with SWR of < 1.25:1
- Telit SE873 GNSS with ceramic antenna on the PCBA
- Full 2W output, using Toshiba AFTxxxx series RF MOSFET as PA,
confirmed range of 10 NM
- Redesigned RX section, easily "sees" targets > 15 NM away depending
on mounting height
- STM32L432 MCU with HAL code
- Running entirely from 12V with onboard buck converter and
appropriate input filter
- TX burst current supplied by 10mF supercap on the PCBA
The design allows the transponder and antenna to be mounted as one piece
somewhere up high, directly onto 1" railing, secured using UV-resistant
heat shrink tubing (3 years and counting, still looks great). The 4-wire
(phone) cable to the cabin travels inside the railing or mast, until it
hits a control circuit where it's converted to USB for feeding into a RPi
or some other similar device. I've had great success with 3.3V level UART
travelling > 35 feet in twisted pair cable with no issues.
I have often thought about commercializing this, but the amount of
regulatory pain here in the US is higher than my threshold (I deal with the
FCC as part of my day job).
What if I made this available as a do-it-yourself kit? I think this would
allow me to dodge the regulatory reef, but it comes with its own
challenges. What would a system like this be worth?
Let's discuss here.
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Thanks for the feedback. For sure, SMD will be a challenge. I'm thinking of bundling a 95% finished PCBA, the antenna, cabling and control box parts, plus instructions for programming firmware (which will be open source, here on github).These will require significant enough assembly to be considered a "kit" but will still be within the reach of a reasonably tech-savvy person. |
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That would be really interesting. As far as I understand a kit can be fairly complete... E.g. I understood the raspberry pi also got started that way (maybe still?). That is also a complete PCB.. just the fact that it was without housing was already enough. What sort of cost are you expecting.. the cheap Chinese versions start @ 200€ already, can imagine this comes close. |
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I may the least capable here just so you know. I have successfully completed some Adafruit projects but I am limited to following detailed instruction and cut and paste scripts. I can even do some basic tings in Linux if i have code to cut and paste. Hardware wise I can connect boards to each other but soldering on a board is a challenge for me. my dexterity and eyesight just isn't what it used to be. And it was probably never as good as I want to think so. But I do feel a sencse of accomplishment even just being able to do the above. |
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Interesting take, @marcelrv. What are you thinking in terms of wireless NMEA? Joining an existing WiFi network on the boat, or being the WiFi gateway for NMEA data? |
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Personally, I always buy wired instruments. We had the option of wireless
wind for the masthead, but we went with wired, one less thing to worry
about.
…On Sun, 30 Aug 2020 at 00:49, Peter Antypas ***@***.***> wrote:
Interesting take, @marcelrv <https://github.com/marcelrv>. What are you
thinking in terms of wireless NMEA? Joining an existing WiFi network on the
boat, or being the WiFi gateway for NMEA data?
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@peterantypas what I personally use on my boat is from this project https://github.com/jeelabs/esp-link Obviously it can be made much more fancy, but it was a very low effort way of avoiding wiring through very hard to get to places on the boat. E.g mast wiring and related through deck connections I find a huge pain in the ** I designed small PCB that contains the needed buck converter and max3232 to go from TTL to serial. Note.. I used jlcpcb for my project... I soldered the smd components by hand. However I think they also offer a fairly low cost and assembly service. ( I'm not affiliated with the guys, nor tried their assembly service, but it would be what I would consider if any of my PCB projects would be in higher demand than <10 units) |
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Here is a photo of the final PCB I installed on my boat. It is very small. I can redo the layout as a Raspberry Pi hat and leave it up to the end user to integrate it as they like. What are your thoughts?
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I think as a Pi HAT is maybe not the best idea, but then you have to take
into account at least 1dB of loss in the cable to the antenna, no one
should put a Pi outside. And there is the AIS aerial which is built in ...
I think the remote unit is a better solution. Personally, I would like the
option of an SMA for a remote aerial on the GPS. The CPS chip antenna works
best when it is flat. If mounted with the board vertical, then the
reception from the back of the board is likely to be poor. I would prefer
some solution that has the option for a remote antenna for the GPS.
Usually they are auto-sensing so it would just need the connection bringing
out to a suitable board edge connector.
Maybe a HAT board that this can piggy back on if needed?
…On Mon, 31 Aug 2020 at 16:50, Peter Antypas ***@***.***> wrote:
Here is a photo of the final PCB I installed on my boat. It is *very*
small. I can redo the layout as a Raspberry Pi hat and leave it up to the
end user to integrate it as they like. What are your thoughts?
[image: IMG_0754]
<https://user-images.githubusercontent.com/1565933/91739575-fb16fa00-eb66-11ea-8760-3b35582e02a7.jpg>
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Here is how the current unit is assembled. Notice the location of the GNSS module and chip antenna. It works great, no need for anything external.
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And here is the final installation on my boat. It's not an ideal photo, but that's the only one I could find on short notice. The transponder is mounted on a 1" fiberglass mast secured to the rear railing. It has performed very well. From an RX perspective, I can see targets > 12 NM away, so I haven't had a compelling reason to mount it higher. Your mileage may vary, of course, but I want to keep it simple for now and avoid adding another wireless module to it (which is another point of failure potentially). My main goal is to create the best possible low cost solution for the boat that has nothing, because I want every boater out there to have one. That's my "vision" if you like.
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Yep, it looks good ... I was just thinking of the people who might want to
put it inside, with antenna outside.
Here is my unit that I built, I did not see anyone else on the list build
one yet ...
[image: image.png]
…On Mon, 31 Aug 2020 at 17:23, Peter Antypas ***@***.***> wrote:
And here is the final installation on my boat. It's not an ideal photo,
but that's the only one I could find on short notice. The transponder is
mounted on a 1" fiberglass mast secured to the rear railing. It has
performed very well. From an RX perspective, I can see targets > 12 NM
away, so I haven't had a compelling reason to mount it higher.
Your mileage may vary, of course, but I want to keep it simple for now and
avoid adding another wireless module to it (which is another point of
failure potentially).
My main goal is to create the best possible low cost solution for the boat
that has nothing, because I want every boater out there to have one. That's
my "vision" if you like.
[image: TransponderOnBoat]
<https://user-images.githubusercontent.com/1565933/91742436-200d6c00-eb6b-11ea-81c3-ea4f29c00cbc.jpg>
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Yeah, this seems to be the prevailing paradigm, and I'm all about shuttering paradigms. There is no compelling reason for the transponder unit to be located inside the cabin. Building it into an IP67 enclosure at the base of the antenna removes the dependency on third party antennas, and offers the best possible performance and user experience. This is straight out of Apple's playbook ;) |
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I had not considered an exterior, all-in-one device. My instinct is to keep electrical bits as far from the wet bits as possible, but I love the elegance of a single sealed unit with its own antenna. great idea! I'm all for it. |
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Yes, I agree, the only problem is the connector joint at the top ... making
that 100% waterproof can be difficult. I know from years of amateur radio
and sailing that water always gets in. I thought about using a potting
compound, or maybe a silicon conformal coating ... on antennas for ham
radio, I use something called "plastidip" on the feedpoint, it is a spray
on rubber coating.
Anyway, I have 4 more sets of components, so building another board would
be easy with a stencil, but if you go the "kit" route, that is OK too. it
would be nice to get the one I built working ... it sees the GPS, and I
think it sees the all the chips OK, but so far I did not see any RF out on
my scope, I'll find some time to try it again. I could see some switches in
the software for test modes, but I forget how far I got with them ...
…On Mon, 31 Aug 2020 at 17:45, Peter Antypas ***@***.***> wrote:
Yeah, this seems to be the prevailing paradigm, and I'm all about
shuttering paradigms. There is no compelling reason for the transponder
unit to be located inside the cabin. Building it into an IP67 enclosure at
the base of the antenna removes the dependency on third party antennas, and
offers the best possible performance and user experience. This is straight
out of Apple's playbook ;)
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On my boat, I have the main antenna at the masthead and a second backup
antenna on the rear arch ... it is always useful to have a backup antenna.
I thought to use the backup for AIS ... in reality, unless you need it
for some rescue purpose or tracking purpose, a range a 1 or 2 miles is
enough for AIS, the reality is you are not going to crash into vessels 10
nm away ... I use half-wave antennas, as the lack of groundplane works
well with this type.
It can be done either way, one more antenna is not a problem, I have HF,
Navtex, GPS, 2 x VHF ... one more is fine.
…On Mon, 31 Aug 2020 at 17:52, mfrostus ***@***.***> wrote:
I had not considered an exterior, all-in-one device. My instinct is to
keep electrical bits as far from the wet bits as possible, but I love the
elegance of a single sealed unit with its own antenna. great idea! I'm all
for it.
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Fully agree... with this size having it as build inside a tube is perfect... Would not go for RPI hat, if anyone want it to connect it to RPI, can just connect the 3 wires. Maybe to support this flavour you may want to have a pin for low volt (3v3) power in, so it would not need the 12V if there is 3v3 / or 5V available from the RPI |
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The PA needs a 28ms 600mA burst at 7.5V for transmission. Currently, this is supplied by an LDO fed from a 10mF supercapacitor which gets slowly charged to 12V and then discharged to about 9V during a packet transmission. To power the unit from 5V, I will need to add a boost circuit with the associated EMI risks, but it's doable. Definitely an option to consider. In terms of cable, I originally used 4-wire twisted pair phone cable. I'm thinking of going to Cat-5 next so there will be enough signals for 2 different voltage options, TX enable/disable function, RX status for LEDs, GNSS status, etc. In my current control box I used an MCU to analyze the NMEA messages for controlling status LEDs. That was probably overkill ;P |
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a kit would be nice, and all you have to do to make it a kit is for the end user to do something to make it work Soldering on a smd fuse or power connector would do the trick A side Q i got in my head is if this could be connected to a chart plotter etc? As for the hat and all in one idea i would not like that, spec if it means i had to get up the mast to do repairs |
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Hi Bo,
The basic idea is the "RF Unit" sends back serial data to a small processor
(Pi, Arduino .. whatever) and the small processor then processes the date
from the RF unit and converts/filters it into a suitable format to feed to
a plotter, eg NMEA 0183, NMEA2000 etc
…On Mon, 31 Aug 2020 at 20:56, Bo Herrmannsen ***@***.***> wrote:
a kit would be nice, and all you have to do to make it a kit is for the
end user to do something to make it work
Soldering on a smd fuse or power connector would do the trick
A side Q i got in my head is if this could be connected to a chart plotter
etc?
As for the hat and all in one idea i would not like that, spec if it means
i had to get up the mast to do repairs
and pi's tend to get a corrupt sd card now and then.
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Update: With the help of a former colleague-turned-consultant (an Apple/GoPro alum), I am finalizing the mechanical aspects of the transponder design to achieve IP68 while still being easy to assemble as a kit. I have updated the EE design to lower the BOM cost and I'll be validating it next week. If all goes well, I should have the new design + updated firmware posted here within a month. The kit will most likely go for sale on tindie.com, but I'm not sure exactly how long it will take. The mechanical design will require a custom moulded part, and that process always takes a couple of months or more. I went sailing today and took a screenshot of the AIS overlay in iNavX for iPad. This should give you an idea of the performance.
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That's great news. |
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Update: Latest board works as expected with a couple of caveats:
That said, I'm not particularly worried about this at the moment. I will validate one more spin of the PCBA and should be ready to update github in the next couple of weeks. I will do this using "git move", so the entire legacy project will move under a "Legacy" subdirectory. The new firmware will have a proper BSP architecture to support new board iterations with little effort. Also, the bootloader will go away and it will rely on ST's ROM bootloader for DFU over UART. I will include a Python script for this. |
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That sounds perfect. The bootloader did give me some issues, but I did
manage to load code over it (I think I wrote some Perl to do this in the
end, as there was no obvious loader script) but it made life harder than it
needed to be, so I won't be sorry to see it go.
…On Wed, 23 Sep 2020 at 17:58, Peter Antypas ***@***.***> wrote:
Update: Latest board works as expected with a couple of caveats:
1. The total output power at the fundamental is +32 dB, so not quite 2
Watts. I could raise it a bit, but:
2. There is a significant 2nd harmonic component that is best
suppressed with a notch at the very output, suggesting that the RF switch
itself is responsible. Even with the notch and duty cycle adjustments, the
level of this harmonic would still violate FCC rules given that it falls
within a restricted band (aviation).
That said, I'm not particularly worried about this at the moment. I will
validate one more spin of the PCBA and should be ready to update github in
the next couple of weeks. I will do this using "git move", so the entire
legacy project will move under a "Legacy" subdirectory.
The new firmware will have a proper BSP architecture to support new board
iterations with little effort. Also, the bootloader will go away and it
will rely on ST's ROM bootloader for DFU over UART. I will include a Python
script for this.
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There was another issue with the current board: Spurious emissions due to improper ramp up and ramp down:
The solution required both a hardware and a firmware change, but things look much better now:
The updates will be in the next revision. Note that there is a 10dB pad at the input of the SA, so add 10dB to all measurements. |
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indeed significant improvement in the 2nd one. Now only very minimal spike left indeed |
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The last issue that makes the design non-compliant (for FCC anyway) is the harmonic signature:
All evidence suggests that the main culprit is the (rather inexpensive) Skyworks RF switch I used (13330-397LF). I was able to get the second harmonic where it is by constructing a single pole notch filter at the output. I am designing a 3-pole notch for the next PCB, so hopefully it will get close to the level of the 3d. That said, I'm not going to worry too much about it. In case you're wondering, there is an extra 10dB of attenuation at the input of the SA, so add 10dB to all measurements ;) |
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Here is why I'm not going to worry about the harmonics:
It turns out that the antenna is such a horrible radiator for the 2nd harmonic that it acts as a secondary notch filter, with an additional mismatch loss of 6dB (or thereabouts). I can see why this would be a concern for a device that connects to a user-supplied antenna, but this is not the case here. So at 3 meters, assuming a normal free space path loss of 32dB, the radiated power of the 2nd harmonic should be -2.1 - 6 - 32 = -37.1dB, and that assumes 100% antenna efficiency. This is still 12dB above the FCC limit, but there is no way that this 27ms "click" in the aviation band will interfere with an aircraft flying hundreds or thousands of feet above your boat :D |
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Would not a simple lpf be easier and more forgiving to component tolerance
than a notch? Swapping the multilayer ceramics in the output filter for
AVX C0G types might help as well.
…On Fri, 25 Sep 2020 at 22:58, Peter Antypas ***@***.***> wrote:
Here is why I'm not going to worry about the harmonics:
[image: Antenna-Broadband-S11]
<https://user-images.githubusercontent.com/1565933/94318868-4cd05b80-ff3e-11ea-8214-5344cdde5bb3.png>
It turns out that the antenna is such a horrible radiator for the 2nd
harmonic that it acts as a secondary notch filter, with an additional
mismatch loss of 6dB (or thereabouts). I can see why this would be a
concern for a device that connects to a user-supplied antenna, but this is
not the case here.
So at 3 meters, assuming a normal free space path loss of 32dB, the
radiated power of the 2nd harmonic should be -2.1 - 6 - 32 = -37.1dB, and
that assumes 100% antenna efficiency. This is still 12dB above the FCC
limit, but there is no way that this 27ms "click" in the aviation band will
interfere with an aircraft flying hundreds or thousands of feet above your
boat :D
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I need at least 30dB of total attenuation in the 2nd harmonic to be compliant, and it can only be effective past the RF switch. I have not been able to devise a low pass filter that will achieve this without at least 1.4dB loss at the fundamental as well, but definitely want to explore this option too. I sent a bunch of boards to JLCPCB for fab yesterday. There are 5 different RF switches and 2 filter configurations in there that I want to try out, so hopefully one of them will work well enough. We may just end up with a design that only transmits at +31dBm, which is still OK, it will have a few miles of range. |
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The downside to a filter after the switch is that the loss also degrades
the noise figure of the receiver. Maybe a discrete PIN diode switch would
perform better than the skytronics switch?
…On Fri, 25 Sep 2020 at 23:58, Peter Antypas ***@***.***> wrote:
I need at least 30dB of total attenuation in the 2nd harmonic to be
compliant, and it can only be effective past the RF switch. I have not been
able to devise a low pass filter that will achieve this without at least
1.4dB loss at the fundamental as well, but definitely want to explore this
option as well.
I sent a bunch of boards to JLCPCB for fab yesterday. There are 5
different RF switches and 2 filter configurations in there that I want to
try out, so hopefully one of them will work well enough. We may just end up
with a design that only transmits at +31dBm, which is still OK, it will
have a few miles of range.
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Yeah, I really wanted to avoid anything between the switch and the antenna. But I got the result I wanted with a pretty sharp, high ripple Chebyshev LPF added to the PA output matching network. So I don't even think I'll need to evaluate other switches. Remember to add 10dB to all these values since there's always an external pad on my SA:
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That looks pretty good to me. 2nd harmonic 45db down should be enough, as
you noted, S11 of the antenna will assist as well.
Slightly jealous that your SA display is much crisper than mine, 8563A?
…On Mon, 28 Sep 2020 at 02:44, Peter Antypas ***@***.***> wrote:
Yeah, I really wanted to avoid anything between the switch and the
antenna. But I got the result I wanted with a pretty sharp, high ripple
Chebyshev LPF added to the PA output matching network. So I don't even
think I'll need to evaluate other switches.
Remember to add 10dB to all these values since there's always an external
pad on my SA:
[image: IMG_0850]
<https://user-images.githubusercontent.com/1565933/94382313-11c25980-00f1-11eb-89ba-0a8b0b03a108.jpg>
[image: IMG_0851]
<https://user-images.githubusercontent.com/1565933/94382317-1424b380-00f1-11eb-9fb9-475d66ff75fc.jpg>
[image: IMG_0852]
<https://user-images.githubusercontent.com/1565933/94382321-1981fe00-00f1-11eb-9d9b-6b2825c48c7a.jpg>
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Update: I got the ROM bootloader to work fine and adapted a Python script from another one of my projects. Unfortunately, the current board cannot enter DFU mode over USART1 because the GNSS is tied to USART2 and is continuously sending data. So even though firmware can enter the ROM bootloader via a serial command, the bootloader immediately shuts down every interface except USART2 because it thinks that's where the firmware update will come from. Oops! I did another board spin to validate the solution, but I totally forgot about the Chinese Harvest festival, so that will take a couple of weeks to get here. |
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The branch "new_design" is already started. I will continue updating it over the weekend and finally push to master. |
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the 6.1 board looks good, The GPS block looks like it might be difficult
to source though.
its way too late here for my brain to work well though ...
…On Sat, 3 Oct 2020 at 03:56, Peter Antypas ***@***.***> wrote:
The branch "new_design" is already started. I will continue updating it
over the weekend and finally push to master.
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Layout looks pretty good. I notice you have swapped to 0603 instead of 0805
after the PA, which should reduce parts inventory ...
the only thing I can see is a few earth vias in component pads that should
be corrected for production I guess, as it makes a paste mess under the
board eventually, but apart from that, nice work dude.
[image: image.png]
…On Sat, 3 Oct 2020 at 05:09, Robin Szemeti ***@***.***> wrote:
the 6.1 board looks good, The GPS block looks like it might be difficult
to source though.
its way too late here for my brain to work well though ...
On Sat, 3 Oct 2020 at 03:56, Peter Antypas ***@***.***>
wrote:
> The branch "new_design" is already started. I will continue updating it
> over the weekend and finally push to master.
>
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That's definitely fixable, do you want to take a stab at it? I can give you commit privileges. |
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More than happy to do that if you like, or I can fork and you could pull
…On Sat, 3 Oct 2020 at 16:25, Peter Antypas ***@***.***> wrote:
That's definitely fixable, do you want to take a stab at it? I can give
you commit privileges.
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Also ... can you check the layer stackup? It looks to me like you have L2
as the 3.3V layer and L3 as the RF groundplane ... I suspect you wanted
those the other way around ...
…On Sun, 4 Oct 2020 at 03:20, Robin Szemeti ***@***.***> wrote:
More than happy to do that if you like, or I can fork and you could pull
On Sat, 3 Oct 2020 at 16:25, Peter Antypas ***@***.***>
wrote:
> That's definitely fixable, do you want to take a stab at it? I can give
> you commit privileges.
>
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That works too.
On Sat, Oct 3, 2020 at 7:21 PM Robin Szemeti <notifications@github.com>
wrote:
… More than happy to do that if you like, or I can fork and you could pull
On Sat, 3 Oct 2020 at 16:25, Peter Antypas ***@***.***>
wrote:
> That's definitely fixable, do you want to take a stab at it? I can give
> you commit privileges.
>
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RE: Layer stackup, that's intentional. I don't remember the exact reason but I had much better luck with this a few years ago than the alternative, so it kind of stuck. I think it had to do with traces being too thin to achieve 50 Ohms between L1 and L2 in a coplanar waveguide configuration. I could be wrong though ... |
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I remember what it was: I wanted my RF traces to be wide enough to encase 0603 pads without creating stubs. Could not possibly achieve that with 0.1mm height between L1 and L2 with any material. I would have needed 0201s instead. Only way to get the "hot" trace to be wide enough at 50 Ohms was using L1 and L3. |
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Could be, it just seems strange to see the 50R output trace with a 3V3
trace between it and the groundplane ... there are no buried vias though
so it would be easy just to rename the layers and try the other way around
when assigning layers at JLC. At the end of the day, its only VHF, so
unlikely to make a whole heap of difference.
…On Sun, 4 Oct 2020 at 04:26, Peter Antypas ***@***.***> wrote:
RE: Layer stackup, that's intentional. I don't remember the exact reason
but I had much better luck with this a few years ago than the alternative,
so it kind of stuck. I think it had to do with traces being too thin to
achieve 50 Ohms between L1 and L2 in a coplanar waveguide configuration. I
could be wrong though ...
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Fair enough, as I said, its only VHF, the track lengths are less than 1%
of a wavelength anyway, so whether they are 100R or 25R "width" probably is
irrelevant. Would be significant at higher frequencies obviously, but at
150mhz, the tracks are too short to be an issue. .. I'm not sure with the
3V3 trace underneath it will quite work as expected, maybe assign a block
of "keepout" on L2 under the RF tracks to prevent the fill from the L2
polygon?
…On Sun, 4 Oct 2020 at 04:35, Peter Antypas ***@***.***> wrote:
I remember what it was: I wanted my RF traces to be wide enough to encase
0603 pads without creating stubs. Could not possibly achieve that with
0.1mm height between L1 and L2 with any material. I would have needed 0201s
instead. Only way to get the "hot" trace to be wide enough at 50 Ohms was
using L1 and L3.
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What about ... L2 before:
[image: image.png]
L2 revised:
[image: image.png]
…On Sun, 4 Oct 2020 at 04:40, Robin Szemeti ***@***.***> wrote:
Fair enough, as I said, its only VHF, the track lengths are less than 1%
of a wavelength anyway, so whether they are 100R or 25R "width" probably is
irrelevant. Would be significant at higher frequencies obviously, but at
150mhz, the tracks are too short to be an issue. .. I'm not sure with the
3V3 trace underneath it will quite work as expected, maybe assign a block
of "keepout" on L2 under the RF tracks to prevent the fill from the L2
polygon?
On Sun, 4 Oct 2020 at 04:35, Peter Antypas ***@***.***>
wrote:
> I remember what it was: I wanted my RF traces to be wide enough to encase
> 0603 pads without creating stubs. Could not possibly achieve that with
> 0.1mm height between L1 and L2 with any material. I would have needed 0201s
> instead. Only way to get the "hot" trace to be wide enough at 50 Ohms was
> using L1 and L3.
>
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That's already the case. There is no power plane anywhere near the RF traces:
BTW, I don't see any of the attachments in your messages. |
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OK, maybe I don't have the latest version from GIT or maybe my eagle
interprets it differently ... but L2 extends right under the RF in my
version .. not sure why github is removing pasted images, thats ..
annoying.
…On Sun, 4 Oct 2020 at 04:57, Peter Antypas ***@***.***> wrote:
That's already the case. There is no power plane anywhere near the RF
traces:
[image: Screenshot from 2020-10-03 20-56-25]
<https://user-images.githubusercontent.com/1565933/95006583-ffe22a00-05ba-11eb-860c-8cfedc02ecb0.png>
BTW, I don't see any of the attachments in your messages.
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For whatever reason my Eagle is not picking up that restrict polygon under
the RF for L2, I suspect it is too old a version :( ...
…On Sun, 4 Oct 2020 at 05:03, Robin Szemeti ***@***.***> wrote:
OK, maybe I don't have the latest version from GIT or maybe my eagle
interprets it differently ... but L2 extends right under the RF in my
version .. not sure why github is removing pasted images, thats ..
annoying.
On Sun, 4 Oct 2020 at 04:57, Peter Antypas ***@***.***>
wrote:
> That's already the case. There is no power plane anywhere near the RF
> traces:
>
> [image: Screenshot from 2020-10-03 20-56-25]
> <https://user-images.githubusercontent.com/1565933/95006583-ffe22a00-05ba-11eb-860c-8cfedc02ecb0.png>
>
> BTW, I don't see any of the attachments in your messages.
>
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I’ll add Gerber exports to git
…Sent from my iPhone
On Oct 3, 2020, at 9:06 PM, Robin Szemeti ***@***.***> wrote:
For whatever reason my Eagle is not picking up that restrict polygon under
the RF for L2, I suspect it is too old a version :( ...
On Sun, 4 Oct 2020 at 05:03, Robin Szemeti ***@***.***> wrote:
> OK, maybe I don't have the latest version from GIT or maybe my eagle
> interprets it differently ... but L2 extends right under the RF in my
> version .. not sure why github is removing pasted images, thats ..
> annoying.
>
> On Sun, 4 Oct 2020 at 04:57, Peter Antypas ***@***.***>
> wrote:
>
>> That's already the case. There is no power plane anywhere near the RF
>> traces:
>>
>> [image: Screenshot from 2020-10-03 20-56-25]
>> <https://user-images.githubusercontent.com/1565933/95006583-ffe22a00-05ba-11eb-860c-8cfedc02ecb0.png>
>>
>> BTW, I don't see any of the attachments in your messages.
>>
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All latest designs and firmware have been pushed to the master branch. Closing this ticket now. |
Peter, this looks like an incredibly cool project. I have a boat, and I'd love to build one of these as the commercial options are expensive, bloated, and gobble up energy.
What's the status of this project?
Have you built and used one, and if so, what has been your experience using it?
Do you want/need contributors to this project? For one thing, a blog, and/or some current documentation might be nice.
So this ticket is really all about asking for a quick refresh of the docs, project status, project needs, etc.
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