[J-core] Fwd: General Questions

D. Jeff Dionne Jeff at SE-Instruments.com
Tue Sep 27 12:26:37 EDT 2016

On Sep 28, 2016, at 12:27 AM, Marina Shishova <thngttr at ya.ru> wrote:

> Hi!

Hi :)

> Hope I write to the right address.
> I do my very first steps with J2 Soft Core, so there are a lot of questions you may find either obvious or too general or maybe too early to be asked but I hope you can answer at least some of them.

Very quickly...

> So, say we do have Aboriginal Linux OS started on Numato Mimas V2 board. What's next?
> 1. How to access hardware like ports/pins, memory, buttons, leds, vga, etc.?

You a, make sure the appropriate IP cores are connected to the appropriate pins and b, write a program or device driver to control said core.

> 2. How to create executable files? Should I write them through terminal connection? Or put them directly to SD card? What IDE and/or toolchain should I use?

Did you build from sources or did you use a precompiled binary?  If you built from source, then you have the compiler installed, otherwise you need to follow the instructions on the j-core.org page and build / install a toolchain (using musl cross make).

> 3. Is it possible to perform project build natively on J2 running on Mimas V2? Is there a way to merge neccessary binaries (like gcc) and libraries with Linux beforehand?

Yes, Rich F demonstrated that (on Turtle) but it’s very very slow.  You want to install the compilers and build on your Linux machine.

> 4. How to load executable binary (hex or elf or other format) from outside to execute within J2 Linux environment?

On mimas, there is no ethernet.  So you can drop the binary on the sdcard and run it from there.  On a platform with Ethernet, you can also FTP the file over to the board.

> 5. Is there any support for DRAM? As you know, Mimas V2 has 512 Mbits of LPDDR, is that memory accessible for J2 for any purposes in current version?

Linux, as you show in your boot messages, runs from DDR.

> 6. We see 511 MB of memory listed during Linux boot (please check the attached screenshot). What does "MB" mean - bits or bytes? Does that value correspond to LPDDR onboard?

Notice the line that says 

Memory: 126068K/131072K available (1993K kernel code...

This is telling you that you have 128MByte of total memory, of which 123MByte is available once the Linux kernel etc has been loaded (5MByte is used).


> Have a nice day,
> thngttr
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