Help with X20 ARM programming

[keenox]

Hello! I played a little with my X20 firmware and the Insignia firmaware and i managed to flash my iriver with the insignia firmware, but it has no sound (more details here) so i switched back to iriver and played a little with it. can someone help me with a good arm editor/compiler, so i can view/modify the iriver firmware? some good arm asm tutorials would also be good as i have never programmed in asm... thank you!

[Llorean]

Rockbox isn't about modifying the original firmware. Please, questions for helping to modify other firmwares don't really belong here.

[keenox]

hmm... aren't we supposed to modify the firmware in order to make a working bootloader for rockbox???

[Llorean]

Rockbox bootloaders are written as stand alone programs. The original firmware isn't modified, usually a case is set up where the Rockbox bootloader is run *instead* of the original firmware, then it may launch the original.

[keenox]

i thought that using the original firmware as a starting point is easier for writing a bootloader... you said that the original firmware may be run after the bootloader. what is this useful for? isn't rockbox supposed to replace the original os? i was planning to modify/rewrite the original firmware in order to make a bootloader as a base for porting. 

[Llorean]

Often users want to dual boot. Sometimes this is because the OF has a feature Rockbox doesn't have yet. So usually an attempt is made to have the player in a state where it can dual boot. This is especially important on some players where Rockbox won't have its own USB access for a while, so the original firmware's USB must be used.

Rockbox is made from the ground up. It does not contain parts of the original firmware. "Modifying" it would be quite contrary to that, as a modification of the OF would, by definition, include parts of it, wouldn't it?

[keenox]

i was meaning that we could use parts of the original firmware in order to use certain hardware. i guess that the firmware programmers know what they are doing and using parts from the OF could help rockbox developers to access different features. isn't it possible, for example, to include the usb functionality of the OF into the bootloader and low-level access it from Rockbox? (i don't really know much about low-level programming, so i apologize if i sound stupid)

[Llorean]

It does not contain parts of the original firmware.

Actually incorporating parts of the original firmware would be a violation of their copyright on it.

[keenox]

i don't think common parts of the software count as copyrighted. for example, if i copy the file access part of a program, does it count as a violation of the author's copyright? that part can be the same in many programs... btw. do you have a messenger id? it's rather unconfortable talking on a forum like this.

[Llorean]

The whole point of the forum is that other people can join in the conversation.

ANY code you write is copyright you. You cannot simply take parts of another person's program and use them without permission.

[saratoga]

i don't think common parts of the software count as copyrighted. for example, if i copy the file access part of a program, does it count as a violation of the author's copyright?

Absolutely.  You cannot take even a single line from someone else's code.  If you're reverse engineering a binary, you can take facts about how the hardware works (register addresses, init sequences, etc), but no code.

Anyway, if you want to learn ARM, the programmers manual for your specific ARM core would be a good thing to start with.  Theres one for each ARM series core on the ARM website. 

[keenox]

thanks! i'll look for the manuals, but i've seen that you have to buy the software. do you know any free gcc->arm or basic->arm compilers? i found references about them on the net, but nothing to download.

[LambdaCalculus]

There's some very useful information on this page:

http://www.rockbox.org/twiki/bin/view/Main/DevelopmentGuide

You can get all the required tools when you prepare a build environment.

Remember, Rockbox is written primarily in C, with some assembler. C++ is used on Rockbox Utility.

[keenox]

LambdaCalculus379 thanks! but as i said before, i must first make a basic bootloader...

[LambdaCalculus]

That's understandable, but if you want to get the idea of how a Rockbox bootloader works, why not read the source code for Rockbox?

Also, read some of the other New Ports threads, and go through the wiki. Take in all of the information you can. Download firmware updates and monitor USB traffic so you can see how the process is done. Come onto IRC and ask some of the devs a question or two.

Information is key, Padawan. Use it to your advantage!

Remember: No firmware modifications, as was told. Use the original firmware only for pointers, not as a basis for programming.