Arduino Forum

Products => Arduino Due => Topic started by: valerun on Apr 14, 2014, 04:22 am

Title: Small-footprint Due
Post by: valerun on Apr 14, 2014, 04:22 am
Hi Guys -

Need your expert feedback on the Due board we are designing.

We wanted to build a smallest possible footprint Due-compatible board for embedding into our products (such as our Open Source EV Charging stations, EV chargers, etc - some info for the curious ones: http://www.emotorwerks.com/products/online-store/product/show/44-emw-juicebox-level-2-15kw-ev-charging-station-kit-or-assembled-unit).

We have sifted through all the posts I could find on various relevant topics to try to collect all gotchas (e.g., errors in Schematics, suboptimal I2C pullup resistor values). We have also looked for various types of user feedback to help us design a board that can not only be useful for us but also could be interesting for others making small production runs based on SAM3X8E. E.g. we have added a 64Kbit EEPROM on board, broken out AREF pin, etc.

At this moment, we were able to get a 4-layer layout containing LQFP-144 package to fit into a 1.2"x1.4" footprint. It would have an external programming board with Due programming circuit on it. This way small production runs are way more economical as you don't have to spend all that $$ and board space on programmer circuits you don't use in production.

See the screenshot below for some details. The picture is admittedly a bit messy with all layers visible - SAM chip is mounted on top of board, all other components - on the bottom. 68 .1" pins on perimeter. Main design objective was the smallest footprint while maximizing the number of peripheral types broken out. The trade-off is a smaller number of broken-out Digital I/O pins. You will also notice there are no reset / erase buttons. Again, we do not expect those to be useful in production environment. And they would take a huge amount of space + cost of electromech components is non-trivial.


In addition to general feedback, would be cool to hear your opinion on some open questions we still have:

* What should we do with VBUS / UOTGVBOF / VBG lines? We are NOT breaking out Native USB at this point so none of the USB hardware would actually be used but I am wondering what we need to keep from the original Due schematics so the system still works. E.g., should we provide VCC to VBUS input? Should we still have an RC network on VBG pin? Etc.

* Should we try to break out native USB? The reason it's not on right now is that a micro-AB slot would take 20% of our board space and in fact would make the board at least 40% larger. Soon enough the space benefit from having this MicroDue board is diminished. So unless one can see extremely high utility for native USB, we would keep it out. IMO given that there is going to be a separate programmer board, native USB is ONLY useful for USB HOST mode. I am just not sure what % of target users this will be important for. Maybe I am missing some uses other than USB HOST?

* Are there any other gotchas we should be aware of?


Thoughts? Would you want something like this? ;-)

Thanks,
Valery.
Title: Re: Small-footprint Due
Post by: luisonoff on Apr 14, 2014, 01:06 pm
This is interesting.
How much do you think it will cost you every fully assembled board?
Title: Re: Small-footprint Due
Post by: graynomad on Apr 14, 2014, 02:01 pm
Any chance of a schematic, it's hard to tell much from the PCB, for example why do you have 5v pins?

______
Rob
Title: Re: Small-footprint Due
Post by: gogol on Apr 14, 2014, 04:45 pm
Title: Re: Small-footprint Due
Post by: dlloyd on Apr 14, 2014, 05:23 pm
If you can include the neglected slave select pin NPCS3 (LFBGA pin A2) for SPI, then it would be possible to use the external decoder support to allow up to 15 peripherals. That one wire could expand SPI peripherals to 4 (or 15 with decoder). It looks like the Arduino software already supports this pin, but its left unconnected on the Due board.

Nice mini-board - I was (am) considering something similar - a mini core board with LFBGA that breaks out all pins.
Title: Re: Small-footprint Due
Post by: valerun on Apr 14, 2014, 08:31 pm
Thanks guys. Will post schematics shortly.

This IS based on 144 lqfp. Very hard to deal with bga without using very expensive pcb process.

5v is there to allow plug into boards with 5v supply.

Good idea on adding usb pins. Would you want the associated circuitry on this board or leave out for the shield?

Same on the 4th spi Cs pin.

Cost wise I expect $13 all in. Assuming good volume of course

Title: Re: Small-footprint Due
Post by: gogol on Apr 15, 2014, 09:28 am
Quote
Good idea on adding usb pins. Would you want the associated circuitry on this board or leave out for the shield?

Depending on space. The most important point would be, to have the pins available.  If there is space left on the board for the circuitry, the shield would be very easy.  Without pins however, the functions are not accessible.
Better leave the circuitry off, if that gives you space for other pins. 

Quote
Cost wise I expect $13 all in. Assuming good volume of course

I assume, that this should be no problem with a good crowdfunding campaign.

Title: Re: Small-footprint Due
Post by: valerun on Apr 15, 2014, 08:20 pm
thx. added a row of pins to break this out. circuitry on board so you just need to connect the pins to VUSB, D+, D-, ID, UGND.  I wonder if there are some creative ways to simplify addition of the connector to these...

Used some extra space to add 4 additional digital pins and better layout for AREF reference.
Title: Re: Small-footprint Due
Post by: valerun on Apr 16, 2014, 07:12 am

  • make VDBU available



what is VDBU pin? It's not in SAM's datasheet...
Title: Re: Small-footprint Due
Post by: gogol on Apr 16, 2014, 08:15 am
Sorry, I missed a "D":   VDDBU ...
Title: Re: Small-footprint Due
Post by: valerun on Apr 16, 2014, 08:35 am

Sorry, I missed a "D":   VDDBU ...



got it. but why would this need to be broken out? why not leave it permanently tied to +3.3V supply?

What might need to be broken out is RTC crystal pads, right? I mean, if we go to the trouble of breaking out NRST, we should make RTC fully functional, right?
Title: Re: Small-footprint Due
Post by: gogol on Apr 16, 2014, 01:15 pm

got it. but why would this need to be broken out? why not leave it permanently tied to +3.3V supply?

Figure 5-3 in the Atmel-Dokumentation shows the purpose, when you wish to connect the backup-batterie like a small coin package.  That may need some kind of solder-pad, where the connection to +3.3V can be cutted/solder-closed as needed.


What might need to be broken out is RTC crystal pads, right? I mean, if we go to the trouble of breaking out NRST, we should make RTC fully functional, right?

Right with that, but the second advantage is, that the NRST is bidirectional, so that external components can be reset through it.
If you connect the external components to NRST they are reset, whenever the reset-controller resets the chip, even when caused by software!  That means, that you need no code, which uses GPIO-pins to reset your peripherals.
Quote from: Atmel SAM3x8E documentation chapter 14.2

• Manages all Resets of the System, Including
- External Devices through the NRST Pin
- Processor Reset
- Peripheral Set Reset


Title: Re: Small-footprint Due
Post by: valerun on Apr 17, 2014, 01:58 am


got it. but why would this need to be broken out? why not leave it permanently tied to +3.3V supply?

Figure 5-3 in the Atmel-Dokumentation shows the purpose, when you wish to connect the backup-batterie like a small coin package.  That may need some kind of solder-pad, where the connection to +3.3V can be cutted/solder-closed as needed.


Thanks. I read through that section but can't understand if there is going to be any residual consumption on rest of VDD pins if the chip is put into a backup mode... If the consumption is zero on all other pins (chip is down, after all), then one could just keep the battery connected to all supply pins at all times. This does assume that the user would move the chip to backup mode once loss of 3.3v external power is detected (perhaps using one of the digital pins to sense that). But this does sound like a kludge. Will try to  break this one out, as well. Running out of space, though ;-)
Title: Re: Small-footprint Due
Post by: graynomad on Apr 17, 2014, 02:42 am
The SAM has a SHDN pin that is supposed to be used to shut down external regulators, that may imply that this should be done to get the best low power operation, but I think it's just to kill external circuitry, the CPU itself has this well handled.

One would assume as you say that the current used on the VDD pins is next to nothing, in fact if you look at Fig 46-4 they have all the VDD pins shorted to GND for testing the VDDBU current, so it's fair to say there is nothing but some leakage current on those pins under a normal shutdown situation.

______
Rob
Title: Re: Small-footprint Due
Post by: valerun on Apr 17, 2014, 03:23 am
ok got the USB pins out (R5, R6 39R resistors fitted on board but varistors don't fit so a shield would have to implement those).

Also got the VDDBU out (bridged to +3.3v - would need to be cut if this feature is used).

Finally, was able to fit in 32khz crystal and caps - at the expense of one digital pin breakout ;-) I just would hate to have sensitive crystal circuitry broken out via huge 0.1" pins...

All this cost ~8% increase in board size. On the plus side, that allowed adding one more analog and a few digital pins

Will post new board and schematics shortly
Title: Re: Small-footprint Due
Post by: valerun on Apr 17, 2014, 06:36 am
...got to stop adding pins...

added one more row on the 109-144 side of the chip which allowed a few additional digital pins but more importantly placing a 3.3v CAN tranceiver to be able to use an excellent CAN-DUE library by collins80 and a few others. These tranceivers run in our EV chargers and work like a charm. So now we have a fully plug-and-play CAN channel on board.

1.4"x1.4" board with 91 pins in 2 rows along the perimeter. The original idea was to have ~40 pins... lol

Sample chips arrived from ATMEL today.

Any other suggestions before we order the first ~10 boards for testing?

V
Title: Re: Small-footprint Due
Post by: gogol on Apr 17, 2014, 08:18 am
That really sounds like a boost-board for the DUE-family. A fraction of the size of the original, with an estimated price, where you have not to think about letting the board in a project.
Title: Re: Small-footprint Due
Post by: valerun on Apr 17, 2014, 06:44 pm
yes, that's the idea.

someone mentioned something about breaking out EBI data bus... What do you guys think about that? Better be very critical as I REALLY  don't want to add a third row of pins
Title: Re: Small-footprint Due
Post by: valerun on Apr 18, 2014, 08:41 am
just checked - full EBI bus is ~50 pins. so perhaps sometime in the future...
Title: Re: Small-footprint Due
Post by: ODwyerPW on Apr 19, 2014, 06:30 am
Will you consider breaking out the Ethernet?
Title: Re: Small-footprint Due
Post by: valerun on Apr 19, 2014, 09:40 am
would RMII be sufficient? 8 pins way better than 16...
Title: Re: Small-footprint Due
Post by: graynomad on Apr 19, 2014, 09:55 am
You want to be careful about feature creep, I've done two Due-compatible designs now and in both cases they got too big and complicated so I ditched them.

OTOH it's a shame not to have all the SAM features :)

______
Rob
Title: Re: Small-footprint Due
Post by: valerun on Apr 19, 2014, 10:33 am

You want to be careful about feature creep, I've done two Due-compatible designs now and in both cases they got too big and complicated so I ditched them.

OTOH it's a shame not to have all the SAM features :)

______
Rob


so true...
Title: Re: Small-footprint Due
Post by: valerun on Apr 21, 2014, 07:32 am
ok RMII is in. Same board size (just reduced number of ground pins in the corners. Sending to PCB house today
Title: Re: Small-footprint Due
Post by: valerun on Apr 28, 2014, 04:55 am
sample boards ordered. 4 sets of:
1. 2x MicroDue V1.1
2. 2x WiFly shield (same 1.4x1.4" footprint)
3. 2x u144 LCD shield (same footprint)
4. 1x MicroDue 'motherboard' in Arduino UNO R3 layout - with USB jack, power input, SPI breakout, second CAN tranceiver (in addition to the first tranceiver that is on MicroDue already)

They arrive next Fri. I plan to populate using our T962A over that weekend and start testing.

Who wants some test boards?

Val.
Title: Re: Small-footprint Due
Post by: Palliser on Apr 28, 2014, 02:55 pm
Hi Val.  A very good initiative. I would like to get involve in the testing of your boards, specially with the EMAC and CAN peripherals.
Regards!

p
Title: Re: Small-footprint Due
Post by: vanduino on Apr 28, 2014, 08:14 pm
My list:

USB Host on native USB port while externally powered (12V Vin).

Persistent RTC with breakout for backup battery.

3mm+ mounting holes in corners.
Title: Re: Small-footprint Due
Post by: valerun on Apr 28, 2014, 08:35 pm

My list:

USB Host on native USB port while externally powered (12V Vin).

Persistent RTC with breakout for backup battery.

3mm+ mounting holes in corners.


thx. the only thing we don't yet have from your list are mounting holes. These would increase the size of the board by 30% (or result in the loss of ~10 pins) which is pretty significant. We are designing this board to be a pluggable MCU board for small production runs - similar to how Arduino Pro Mini or Spark.io boards are used...

But pls let me know if you have some creative ideas.

thanks,
Valery
Title: Re: Small-footprint Due
Post by: gogol on Apr 29, 2014, 09:47 am
In a kickstarter project the same discussion ended with that solution:

https://www.kickstarter.com/projects/214379695/micro-python-python-for-microcontrollers/posts/727834
Title: Re: Small-footprint Due
Post by: pjrc on Apr 29, 2014, 10:12 am

A fraction of the size of the original, with an estimated price, where you have not to think about letting the board in a project.


As someone who makes ARM-based Arduino compatible boards (but not with Atmel SAM3), I'm curious what price point you'd consider low enough to just leave the board in a project?
Title: Re: Small-footprint Due
Post by: valerun on Apr 29, 2014, 10:16 am

In a kickstarter project the same discussion ended with that solution:

https://www.kickstarter.com/projects/214379695/micro-python-python-for-microcontrollers/posts/727834



nice! thx for linking!
Title: Re: Small-footprint Due
Post by: graynomad on Apr 29, 2014, 10:43 am
Quote
mounting holes. These would increase the size of the board by 30%

How about having mounting tabs like the board on Gogol's Kickstarter link, they can snap off if not wanted.

______
Rob
Title: Re: Small-footprint Due
Post by: vanduino on Apr 30, 2014, 03:44 am
re: Mounting Holes

I can appreciate keeping the size to a minimum, so I understand your hole aversion.

I work with mobile projects: vibration and temperature swings. The board would have to be removable, therefore pin headers. I haven't seen many pin headers come loose, but I worry about them over time. So I like the idea of a removable module that can be locked down. How about one bolt hole near the center, can you squeeze that in?
Title: Re: Small-footprint Due
Post by: valerun on Apr 30, 2014, 03:53 am

re: Mounting Holes
How about one bolt hole near the center, can you squeeze that in?


center hole will be tough as the entire center of the board is taken up by a huge SAM3X8E chip ;-)  We tried to work BGA-144 in and gave up ;-)  LQFP is a 1x1" package (with leads)

In our designs using Pro Mini today, we actually solder in the Pro Mini board to the main board. No worry about pins loosening and also saves spend on mating connectors.
Title: Re: Small-footprint Due
Post by: vanduino on Apr 30, 2014, 04:50 am
Cannot afford to solder such a module to a motherboard that will go through option/revisions/updates in its life cycle. Has to be swappable. Mounting hole does not need to be large or dead center, just helps to keep pin headers from creeping loose.

You get the picture, I wont belabor it. Good luck with the project. Will be a welcome addition to the family.
Title: Re: Small-footprint Due
Post by: valerun on May 04, 2014, 05:35 am
quick update - first sketch!

https://www.youtube.com/watch?v=kPL8APZyh4A

playing pick-and-place with 0402 parts is a b*tch ;-)

will confirm USB upload next week and will be ready for small production run I think...

Title: Re: Small-footprint Due
Post by: Palliser on May 04, 2014, 07:33 am
:smiley-eek-blue: Wow. Awesome video! One small foot-step for eMotorWerknstein, one giant leap for the Arduino Due based-kind!

p
Title: Re: Small-footprint Due
Post by: valerun on May 04, 2014, 08:14 am

:smiley-eek-blue: Wow. Awesome video! One small foot-step for eMotorWerknstein, one giant leap for the Arduino Due based-kind!

p


;-))

thanks P. the idea is to do a bunch of tests now for every periphery and pin. Ideally I would get ~100 of these made and shipped to people like you to test. The only snag is that we don't (yet) have an SMT lab here and contracting a 100-unit run will cost us ~$2,500 in fixed labor costs. Trying to figure this out now
Title: Re: Small-footprint Due
Post by: valerun on May 05, 2014, 05:14 am
guys - couple of questions as we are finalizing design:

1. is CAN termination resistor (120R) needed on this board? If it's connected to fully configured CAN bus, one would have to desolder 0402 part from the board...

2. As you saw in the video (https://www.youtube.com/watch?v=kPL8APZyh4A), the idea is to have a separate landing board in the UNO format. That board would provide micro-USB connection, ability to power from 7-12V source, etc. The question is what else we should provide on that board. For now, we have added a second CAN tranceiver - after all, most of our own uses will be automotive-related. What else?

3. If you were really paying attention to the video, you could spot a few MicroShields on the PCB array. At the moment, we have a WiFi MicroShield and a LCD MicroShield. What else could be interesting?

Any other thoughts?

V.
Title: Re: Small-footprint Due
Post by: Palliser on May 05, 2014, 03:29 pm


1. is CAN termination resistor (120R) needed on this board? If it's connected to fully configured CAN bus, one would have to desolder 0402 part from the board...

2. As you saw in the video (https://www.youtube.com/watch?v=kPL8APZyh4A), the idea is to have a separate landing board in the UNO format. That board would provide micro-USB connection, ability to power from 7-12V source, etc. The question is what else we should provide on that board. For now, we have added a second CAN tranceiver - after all, most of our own uses will be automotive-related. What else?

3. If you were really paying attention to the video, you could spot a few MicroShields on the PCB array. At the moment, we have a WiFi MicroShield and a LCD MicroShield. What else could be interesting?



Hi Val.

My answers:
1. Yes. A termination resistor 120R is necessary. Normally, a select jumper is used in series with it to select it or not.

2 & 3. Think about adding an Ethernet PHY as a separate module (similar to the one from elechouse) or soldered in your UNO landing board.

http://www.elechouse.com/elechouse/index.php?main_page=product_info&products_id=2229 (http://www.elechouse.com/elechouse/index.php?main_page=product_info&products_id=2229)

See also replies 66 and 92 for schematic and example.

http://forum.arduino.cc/index.php?topic=142908.0 (http://forum.arduino.cc/index.php?topic=142908.0)

I am also adding an 2.8 LCD TFT to Due but need ebi.

Regards!

p
Title: Re: Small-footprint Due
Post by: valerun on May 05, 2014, 10:30 pm
thanks P. will keep 120R on. jumpers will be tough - no space - so will have a trace one would have to cut (restoration would be possible by wire-jumping two small vias)

ETH PHY as shield is a good idea. Don't want to burden the landing board too much as it's likely going to be shipped with every MicroDue board and will be really sensitive to cost.

Unrelated question but hopefully some of you guys have perspective on this. We are exploring possibility to lease some in-house SMT assembly equipment for small / proto runs. Any recommendations? Has to have automatic pick and place...
Title: Re: Small-footprint Due
Post by: valerun on May 05, 2014, 10:46 pm
P - I have read your thread on ETH in its entirety a few days ago. You are doing truly amazing work for the community (ETH, CAN, etc...).

Sadly I can't figure out sourcing for DM9161 chip...
Title: Re: Small-footprint Due
Post by: valerun on May 05, 2014, 11:46 pm
quick question: how bad would it be to deviate from 0.1" pitch on external pins for MicroDue board? Right now those pins take up HALF of the board space by surface!

For example, we could use same spacing as XBee (2mm) and save some overall space and use space in the corners for mounting holes...
Title: Re: Small-footprint Due
Post by: Palliser on May 06, 2014, 02:31 am

P - I have read your thread on ETH in its entirety a few days ago. You are doing truly amazing work for the community (ETH, CAN, etc...).

Sadly I can't figure out sourcing for DM9161 chip...


Val- In case that you decide to add the EMAC peripheral to one of your boards, I'd rather recommend to use one Micrel PHY like KSZ8051MNL given Micrel's better hardware integration and available documentation.

http://www.micrel.com/_PDF/Ethernet/datasheets/ksz8051mnl-rnl.pdf (http://www.micrel.com/_PDF/Ethernet/datasheets/ksz8051mnl-rnl.pdf)

p
Title: Re: Small-footprint Due
Post by: valerun on May 06, 2014, 08:06 am
P - if you come up with schematics to connect to my RMII pinout, I promise I will make the shield ;-)
Title: Re: Small-footprint Due
Post by: JWScotSat on May 06, 2014, 12:11 pm
Great work, I'm currently working on a project that requires 2 Dues interconnected on a PCB. This would be a huge space saver for us. We'd definitely be interested in a low cost solution. Will keep track of your progress!
Title: Re: Small-footprint Due
Post by: Palliser on May 06, 2014, 08:44 pm

P - if you come up with schematics to connect to my RMII pinout, I promise I will make the shield ;-)


No problem Val. I kept running DM9161 and KSZ8051MNL PHY chips with DUE some months ago without problems but the sketches and libraries still raw. I needed ten pins from the DUE but I believe MMI pins (MDC/MDIO) are not necessary (I need to verify that). Anyway, please, confirm to me the broken out EMAC pins of your DUE-based board as follows:

PIN NAME                              DUE PIN
-EREFCK: Reference clock pin-----------113 ETX_CLK
-ECRSDV: Carrier Sense/Data Valid------119 ERX_DV
-ERX0: bit Receive Data----------------120 ERXD0
-ERX1: bit Receive Data----------------121 ERXD1
-ERXER: Receive Error------------------122 ERX_ER
-ETXEN: Transmit Enable----------------114 ETX_EN
-ETX0: bit Transmit Data---------------115 ETXD0
-ETX1: bit Transmit Data---------------118 ETXD1

Thanks,
p
Title: Re: Small-footprint Due
Post by: valerun on May 07, 2014, 12:53 am


P - if you come up with schematics to connect to my RMII pinout, I promise I will make the shield ;-)


No problem Val. I kept running DM9161 and KSZ8051MNL PHY chips with DUE some months ago without problems but the sketches and libraries still raw. I needed ten pins from the DUE but I believe MMI pins (MDC/MDIO) are not necessary (I need to verify that). Anyway, please, confirm to me the broken out EMAC pins of your DUE-based board as follows:

PIN NAME                              DUE PIN
-EREFCK: Reference clock pin-----------113 ETX_CLK
-ECRSDV: Carrier Sense/Data Valid------119 ERX_DV
-ERX0: bit Receive Data----------------120 ERXD0
-ERX1: bit Receive Data----------------121 ERXD1
-ERXER: Receive Error------------------122 ERX_ER
-ETXEN: Transmit Enable----------------114 ETX_EN
-ETX0: bit Transmit Data---------------115 ETXD0
-ETX1: bit Transmit Data---------------118 ETXD1

Thanks,
p



Yes, I have these exact pins broken out. I looked at the BOM for Micrel-based shield and I think we could offer a ETH MicroShield at $15-20 pricing point
Title: Re: Small-footprint Due
Post by: Palliser on May 07, 2014, 03:04 pm


Yes, I have these exact pins broken out. I looked at the BOM for Micrel-based shield and I think we could offer a ETH MicroShield at $15-20 pricing point


Man, that would be a good deal considering that some Micrel distributors sell the KSZ8051MNL small eval board for more than US$100.

p
Title: Re: Small-footprint Due
Post by: valerun on May 08, 2014, 12:08 pm
FYI we were talked out of 2mm pitch pins. So 0.1" pitch it is.
Title: Re: Small-footprint Due
Post by: JWScotSat on May 08, 2014, 02:19 pm
Do you have any timescale on when you might know the pricing?
Title: Re: Small-footprint Due
Post by: valerun on May 09, 2014, 08:23 am
I am relatively certain it's going to be below $25 for the MicroDue board
Title: Re: Small-footprint Due
Post by: dkrenzel on Jun 15, 2014, 09:59 pm
Are there by chance schematics available yet for the MicroDue board?
Title: Re: Small-footprint Due
Post by: valerun on Jun 15, 2014, 11:59 pm

Are there by chance schematics available yet for the MicroDue board?


Thanks for your interest!

Not yet - board is still in testing.

We should have some good updates in the next 3-4 weeks. Production is ready to go as soon as we get it through testing.

V
Title: Re: Small-footprint Due
Post by: Palliser on Jul 10, 2014, 04:26 am
Hello Val!
I hope everything is going well with your tests of the small-footprint Due. I am eager to work with it and specially interested in the CAN bus functionality. Regards,

Title: Re: Small-footprint Due
Post by: Palliser on Oct 19, 2014, 01:58 pm
Hello Val! ANy news on the Small-footprint Due? Thanks.
Title: Re: Small-footprint Due
Post by: paperslammer on Oct 22, 2014, 02:12 am
Nice work - this is something I am interested in as well.
Title: Re: Small-footprint Due
Post by: bobcousins on Oct 25, 2014, 01:27 pm
I would be interested in this too, but it seems to have disappeared down a black hole.

I might have a go at designing something similar.
Title: Re: Small-footprint Due
Post by: bobcousins on Oct 25, 2014, 05:45 pm
I made a start :)

ETA: Just for the archives my version of "MicroDue" morphed into "CoreSam3x" and I started a new thread http://forum.arduino.cc/index.php?topic=275705.0
Title: Re: Small-footprint Due
Post by: asimlink on Jul 03, 2015, 02:13 pm
Hi Friends,

I did an Arduino Due compatible design based on ATSAM3X8E but somehow USB interface is not working.
I have my schematics and the detailed issue posted here:

http://forum.arduino.cc/index.php?topic=328843.msg2269583#msg2269583

Since you guys have experience of making a smaller Arduino Due board, can you please help figure out what might be the issue with my design?

Thanks