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General Questions to 86duino One Bios
2015 年 07 月 19 日
10:48:09
Alex
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2015 年 07 月 18 日
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I'm thinking to buy X86Duino one including the VGA Card. My motivation is to learn about the software side (low level) of X86 embedded systems. In this context I have a lot of questions and hope someone can answer them.

1) Is the result of build coreboot a complete Firmware Image which could be flashed to the 86duino one board ?
2) Are there some closed source/precompiled parts inside or can I study the complete source?
3) Does the generated image contain a VGA Bios, so the VGA stays functional?
4) The arduino layer is based on freedos, which is contained in the flash (virtual drive A??). Does the generated bios image contain this part also?
5) Someone here said that the JTAG interface is not a standard one, but what is about the SPI Flash Chip? Is it possible to read the chip without desoldering? The 16 golden pins (for an alternative flash package?) around the flash chip are perfect to connect some wires. Does the CPU start if I apply the power to the flash-chip? Can I hold the cpu in reset state manually while reading the flash?

thank you in advance and sorry for asking too much questions and my bad english.

2015 年 07 月 20 日
19:49:22
George Andrews III
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2015 年 03 月 13 日
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Hello, Alex.

I have no clue what you're talking about in the first question. What do you mean by "coreboot"? For the second question, I answer no; the BIOS and internal operations can be learned in the Intel Software Developer's Manual (because Vortex86EX is based off of the Pentium II). You should also have a look at the Vortex86EX datasheet. It contains information about the registers, system busses, and general information about how the processor works. For the third question, are you talking about Sysimage when you say "firmware"? If so then yes, the firmware does support the MiniPCIe VGA Card which is designed for the 86Duino One. I'm not entirely sure how to answer your fourth question. What do you mean by "the Arduino layer"? And here is what gets me really confused: what do you mean by "generated BIOS image"? Are you talking about the boot loader which is stored in the processor's cache? For your fifth question, I simply don't know. I have never tried to do this before. I would not recommend trying; you could break something.

Best of luck.
George

2015 年 07 月 21 日
00:35:11
Alex
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2015 年 07 月 18 日
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Thank you for your reply,
sorry for my unclear expression.

what I'm talking about is this repository: https://github.com/roboard/build-coreboot/blob/master/README

To make it simple: can I recompile the complete BIOS+Bootloader from this repository and get an image which I can use to update 86Duino one, without loosing any functionality. (correct crossbar settings, BIOS int 10h for VGA, the freedos-drive (A) in SPI Flash). Are there some precompiled parts inside (so I cannot read the complete source).

If this is not the correct repo, where I can find the correct one?

Regarding the last question: "what should I do if my coreboot modification would brick the system?". Desolder SPI-Flash and make a backup with external programmer and in a case of brick, desolder the flash again to reprogram it with backup should be the safest solution, but also the most complex one. Maybe there is a simpler solution without desoldering the flash? What I was thinking about is to simply connect some wires to the golden pins around the flash chip (the board is powered off) and make a backup or write it back via SPI, but to do this I have to apply power to the VDD/VSS pins and this will maybe power up the cpu, which can also try to access the spi-bus... On some microcontroller boards it's possible to do this by simply holding the cpu in reset state (reset-pin active) all the time, but I don't know if such solution is working with this soc.

Thank you in advance

2015 年 07 月 21 日
02:08:26
George Andrews III
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2015 年 03 月 13 日
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I don't see any reason why you shouldn't be able to do that. However, since I never tried that myself, I am not 100% sure that the code is open-source (so you can compile it manually). Feel free to try it out, though. Your solution to an SPI Flash failure looks good, too. Go ahead and do what you want to do. Once you have done that, I would like to hear how it turned out.

Thank you,
George

2015 年 07 月 29 日
01:52:39
Glaux
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2013 年 10 月 11 日
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Hi Alex,
have a look on my older threads releated to coreboot (I have Zero board), your questions was answered there. In the past, the coreboot contained a closed source binary ext. ROM for drive A: emulation but it was later replaced with opensource code. AFAIK the current state is that you should be able to rebuild the entire coreboot image and flash it (also you need properly configuerd crossbar binary block, it needs pay attention on several build steps). Unfortunately I didn't find a free time to try myself yet but sure I will try.
The question about reflashing SPI flash - I was done some experiments with CB and it resulted to brick the device (due to bad crossbar config or so) and I had to desolder the chip and flash it by external programmer (I made a tool called SPIPGM some years ago). It's even a bit more complicated because the used SPI flash is 1,8V device so you need a voltage level translator to interface it. I don't know much about the used JTAG but it was told that it needs some very expansive device so forgot it.

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