woo, lots going on haven't stopped writing answers to questions since we launched yesterday. feel free if you have any questions, ask away.
I wanted to see the schematics, and I see an a31 folder but no a20 folder, and a file called "EOMA68_A31.pdf" however it is dated 2013 and labelled Allwinner Technology Co Ltd.
Is that the correct PDF, or should I be looking at a different one?
it's probably in the A10 folder.... the CPU Card itself isn't the thing you need to be looking at though (except out of curiosity or if you want to ignore the standard, which you can do), the *other side* though - where you'd want to make your own base boards, that's much more interesting. hmmm... looking around news i'll need to take a look.
what is it exactly that you'd like to see?
I see a link that says:
- EOMA68-A20 Schematics and PDFs contains the complete set of datasheets for the EOMA68-A20 Computer Card
but it goes to a location where I can see many files, but not the A20 Computer Card or A10 folder.
I wanted to see the schematic to learn more about the product that will be supplied. Also I don't want to end up with a paperweight if the overall project ceases and any forums die one day, i.e. the schematics will allow me to continue to benefit from the Computer Card when there is no technical support. . The page states that it is available, but I can't find it. Is there a precise URL that I may be missing for the PDF schematics?
Just as an example I recently contributed to the Lime SDR funding campaign but I didn't do so until I had examined its schematics and then the main component datasheet and register examination, so I could see precisely what it featured for the sum of funds demanded. I was satisfied I would be able to make use of it and that it was worthwhile so I contributed accordingly.
cool, great! ok i'll fire up the VM and generate a PDF, it's been so busy i've not had time to keep everything up-to-date, but the EOMA68-A20 CPU Card is the one exception where, to ensure that the investment is recovered and that manufacturing is not disrupted by third party suppliers, i'm *not* releasing the full schematics and PCB files... yet. which is why you haven't been able to find them uploaded, there. a PDF of the schematics, not a problem. give me a mo. btw please bear in mind, this will be the one with four 8x DDR3 RAM ICs, and i'll be doing a redesign to use two 16x DDR3 ICs - it's a lower-cost layout.
okay! so, i created an a20 directory http://hands.com/~lkcl/eoma/allwinner/a20 - the PDF schematic's there for review. background: we had an extremely competent engineer (one of wits-tech's absolute best) put that together initially, and i've been maintaining it since, having taught myself how to do PCB CAD over the past four years. some of the pages (page 1-4 for example) are a leetle out-of-date, but you get the general idea. you can actually find schematic PDFs of various tablets around: they will look reaally similar, also if you compare to the cubieboard schematics they will look *really* similar
page 5 is DDR3 connectivity (and power) for the A20
page 6 is general A20 GPIO, JTAG, and other peripherals such as HDMI, NAND, SPI, SD/MMC etc.
page 7 is the AXP209 Power Management IC
page 8 is some of the SOT23-5 and SOT-23-6 discrete PMICs needed (1.5v, 3.3v, 2.5v)
page 9 is pull-ups, XTALs, all stuff that needs to right next to the A20
page 10 is the 4x DDR3 8-bit RAM ICs (to be replaced with 2x DDR3 16-bit)
page 11 is the NAND IC, Micro SD/MMC card connector and Micro-USB-OTG
page 12 is the HDMI connector PLEASE NOTE: the RTL8201 has been REMOVED
page 13 is the EOMA68 connector, bless 'im our engineer who made this didn't speak very good english, he left it as "LCD", i just haven't had time to rename it
basically it's incredibly similar to the cubieboard, just less busy because EOMA68 is a simple standard. it should be clear though that the actual important stuff is the EOMA68 connector and the other connectors... *not* the actual processor, RAM or NAND. you've looked at some of the other PDF files (for the A31 for example) so that should be clear: they're all the same EOMA68 connector. the only exception to this would be if you needed to *NOT* conform to the EOMA68 standard. for example, you noticed that one of the pins on the EOMA68 connector had some other multiplexed functionality by going over the A20 datasheet, and that was something that you specifically wanted to use, and were happy to be making your own baseboard that wasn't compliant with the EOMA68 specification.
why would that be beneficial? well, the plan here is to ramp up to mass-volume, so that these end up being sold in best-buy, walmart, staples and other supermarkets, at really *really* competitive prices. "just go buy an upgrade computer card" like you would say "just go buy a bigger memory card".
what *that* means is that as an engineer you could literally walk into a supermarket and buy their entire stock of computer cards to fulfil a tight customer deadline! but not with something that has bits sticking out of it at least 12mm high: the component clearance on the EOMA68-A20 is only about 4mm.
anyway - hope that helps, i leave to you it.
doh! sorry - sorted used rsync to copy it up, it often sets permissions to rw-------.
found a comparable cubieboard set of schematics http://dl.cubieboard.org/hardware/cubieboard_schematic_2012-08-08.pdf
also there's a maaassive set of resources here http://docs.cubieboard.org/resources
many of which will be relevant because it's the exact same processor, memory layout (planned) - i often run the cb2 images and kernels directly on the EOMA68-A20 with little or no modifications.
I'm afraid I've given up. I tried accessing the new URL, and I see this:
Besides, the URL states they are August 2012 schematics.. Is the project really using 4-year old technology?
A major benefit of your project is supposed to be freely available 'everything'. But I feel I'm getting fobbed off with schematics dated 2013 according to the title block (despite the file name containing the number 2014) of the previous link you supplied (Index of /~lkcl/eoma/allwinner/a20 )
Where are the PDF schematics to the actual board, or the current revision board, in PDF format?
If they are not going to be available to users, that's alright, it is your choice, and I wouldn't have tried looking for the schematics. I only looked because it was stated that they were available, and a key part of your project are the statements like the ones below, and it was merely prudent to examine first before potentially funding. If I misunderstood and they are not to be made available just yet, then I apologise. But I feel it could have been made clearer right from the start.
- Truly Free: Everything is freely licensed
"we will NEVER compromise on our commitment to libre principles: you will always be able to repair your own EOMA68 devices by 3D printing replacement casework parts; you will always have access to the source code and the PCB CAD files"
"Many projects claim a degree of “open-ness”, using the word “open” in order to attract users and developers, but a simple in-depth investigation of such projects quickly reveals the claim of “open-ness” to be misleading or outright false."
"A commitment to being fully Libre is a critical strategic part of this project. We are working with the FSF to apply for RYF Certification of the Libre Tea Computer Card for example, but are also going way beyond that by providing full CAD files, schematics, and datasheets for all the parts (without NDAs) as well as having the 3D CAD files for the casework as a completely open GPLv3+ licensed project right from its inception."
- EOMA68-A20 Schematics and PDFs contains the complete set of datasheets for the EOMA68-A20 Computer Card
aww tooom, grrr, he's got a bad link on the cubieboard site (which is nothing to do with me btw). i assumed he'd be keeping his site up-to-date *sigh* give me one second to find (and check this time!) cubieboard schematics... ok google "cubieboard schematics" and there's one that i've just double-checked downloads (it's a copy from someone else's web site) http://cdn2.boxtec.ch/pub/iteadstudio/cubieboard_schematic_2012-08-08.pdf
if you really can't download that (i.e. if someone deletes it before you get a chance to), please do google it for yourself ok? you should be able to use archive.org as a last resort.
> Is the project really using 4-year old technology?
yes. it began over five years ago. you can see the archives of the news site date back that far: for this *one* sub-project (the EOMA68-A20 Computer Card) it has its own news site, here: news
it's taken that long to get the standard stabilised. we raised $15,000 to get that first revision done, then a further $2,000 for the second revision (after having to make changes to the standard), then another $2,000 for the third revision, each with approximately a year between each one as i have had full-time jobs to help pay for all these board designs and much more.
> But I feel I'm getting fobbed off with schematics dated 2013 according to the title block
you're not. i'm up to revision 2.2 of the board, and will be moving to revision 2.5 for the 2x16-bit DDR3 layout. remember, this project has been going on for a LONG time, i've been talking about it on the arm-netbooks mailing list (see lists.phcomp.co.uk), but i have been too busy to be on other forums to let people know what's been happening. i'm taking a break from design work to manage the campaign communications and keep up-to-date (full-time) with the various forums.
> Where are the PDF schematics to the actual board, or the current revision board, in PDF format?
if you want the revision 2.5 ones, that's basically exactly the same but with the 2x DDR3 16-bit blocks moved off the *top* of the page at the moment because i'm still working on them. basically i was able to find someone else's .SCH design which had the same DDR3x16 RAM ICs, and cut/paste those in.
i am *ONLY* changing the DDR3 RAM ICs between the 2.2 and the 2.5 revisions. NOTHING else. so the 2.2 revision schematics, because they're completed, are actually more useful.
> If they are not going to be available to users, that's alright, it is your choice, and I wouldn't have tried looking for the schematics.
you have the current schematics for the current stable board. i can generate the current schematics for the current board in development if you like but it's a work-in-progress where stuff will be off-page and not visible: basically it'll look exactly the same as the 2.4 revision but with the 4 DDR3x8 ICs missing, and a whole stack of disconnected netlists.
in the bit you quoted you missed out the bit about the possibility of third parties taking the PCB designs and creating competing product runs, which is something i can't let happen. *everything else* - base-boards for the tablet, the laptop, the micro-desktop, those *are* all available (and are actually more useful to people who may wish to make their own base boards), they have their own separate news page, place where i keep the datasheets and schematics and so on. *AFTER* the investment of the past five years has been recouped in some way *THEN* i will release the CAD files of the CPU Card.
i'm working on this project pretty much on my own - there used to be some help but they gave up. i can't do everything myself, so i make do. if this was a VC-invested effort it would have been completed and to market years ago. but, it would not be an eco-conscious project if it was VC-backed, that's for sure.
you have the current schematics for the current stable board
Except that I don't. Your file at Index of /~lkcl/eoma/allwinner/a20 has a 13-page PDF from 2013 by AllWinner, where you've removed pages 14-21 (they are still listed on the content page) and the remainder pages still refer to GPS, WiFi and other features which your project page does not state are present. Are those pins now used for something else, a new feature perhaps, or left disconnected?
I would not need to ask, nor would I need to guess, if you actually had supplied the actual PDF schematics for your current board..
> Except that I don't.
yes, you really do.
i'm not trained as an electrical engineer, i'm a very busy software engineer who's had to work full-time on other jobs whilst doing this part-time (including learning how to do PCB CAD design, from scratch).
> has a 13-page PDF from 2013 by AllWinner
because i don't know how to change the name, and it was Reference Designs supplied by Allwinner, to Wits-Tech (who also didn't change the name), and it's not important to the functionality of the board, so i've left it there.
> where you've removed pages 14-21 (they are still listed on the content page)
because i don't know how to change the page numbers
> and the remainder pages still refer to GPS, WiFi and other features
because i left them in as they're not important to the functionality of the board, and i'm short on time. remember, i'm *not* trained as an electrical engineer, and i'm not being paid full-time to do this work "for a client", i'm doing this for myself. so anything that saves time, i've left it alone.
remember there's NOBODY ELSE working on this with me, and i have to do the casework (learned from scratch how to do 3D CAD design), source the components (2 years), keep the suppliers happy, get quotes, get the crowdfunding up and running - it's a hell of a lot of work.
if you'd like to help clean up the schematics i can send you the PADS .sch file.
> which your project page does not state are present.
that would be a good indication that they're not going to be included in the project.
> Are those pins now used for something else, a new feature perhaps, or left disconnected?
left disconnected. you may be confused because a normal single-board computer would be using those functions. this is cut down to the bare minimum, then USB, SPI, I2C and SD/MMC devices are connected on the peripheral board, not the main computer card. it *really is* this simple, so a lot of stuff gets cut.
> I would not need to ask, nor would I need to guess, if you actually had supplied the actual PDF schematics for your current board.
i _have_ supplied the actual PDF schematics for the current board. it really is as bare-bones as it looks. the PCB size is 43mm x 70mm x 1.2mm thickness: you can see on the crowdfunding page how tiny it is. there isn't room for WIFI, GPS or other chipset. it's PMIC, CPU and RAM on the top, connectors on the ends, and one NAND IC on the back. *that's it*.
that really is all there is to it. everything else is left disconnected.
the reason why it's this bare-bones is because EOMA68 is designed as lowest-common-denominator across a wide range of low-power low-cost SoCs. there's one from ICubeCorp - the IC1t - that is only a 176-pin QFP. i *barely* managed to get it into EOMA68 form-factor on its pincount. i think there was like maybe one spare GPIO pin left.
whereas the A20 is 441 pins, a whole stack are therefore completely unused. SATA, Ethernet, 2nd LCD interface, TS0, TS1, VGA - all left disconnected.
hi shabaz, how did you get on reviewing the archive news so that you could verify the history of this board's development? would you like me to send you the SCH file (which i can export to PADS ascii format) so that you can help clean it up?
ok after reviewing current shenzen prices of 8 gigabit DDR3x16 RAM ICs ($9 in qty 500) vs 4 gigabit DDR3x8 RAM ICs ($2.95 in qty 500) the cost of putting in 2 GBYTEs of DDR3 RAM at this 800/1033 mhz level would be a whopping $18 using the planned 2x DDR3x16 ICs compared to $12 for 4x DDR3x8. we can't use more common DDR3x16 1600mhz or greater because they won't go down to the 800mhz level which we'll need for both power-saving as well as "play it safe" reasons...
... so ironically i will be sticking with the original design and just adding an extra address line. so this is very similar to what is on the Cubietruck (aka Cubieboard 3). the Reference Design that everyone is working from only had 14 address lines for the 4x DDR3x8 which only allows up to 1 GBYTE memory addressing... i'll have to squeeze in an extra address line somehow! should be ok...
hi folks after the discussion came up a while ago here on element14 about EOMA68 i thought you might appreciate knowing that the crowdfunding campaign will start tomorrow and run for two months. i have a heck of a lot to do so here are a couple of links http://crowdsupply.com/eoma68 and http://rhombus-tech.net/crowdsupply/ - we'll have a micro-desktop housing, a 15.6in laptop housing and a computer card with 2gb RAM, 8gb NAND and an Allwinner A20 dual-core ARM Cortex A7 running at 1.2ghz.