Rockbox Development > New Ports

Creative Zen Vision:M

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Bagder:
The ARM core certainly is powerful enough to drive audio-only codecs fine on its own. The DSP is only really necessary to use for video. Possibly it is good to use for audio too to get the power consumption to a lower level.

But in the Neuros case and with their DM320 chip (I don't know if there even exist different versions, but I can't exclude that risk) the DAC is controlled by the DSP core so there cannot be any sound without at least some basic DSP code that gets PCM data from the ARM. But again, I'm  not sure if that is truly a chip limitation or something they opted to go with.

And yes, reverse engineering will reveal lots of stuff but the DSP code will of course require its own challenge of DSP-specific reverse engineering.

To compare with Neuros again, they intend to have a binary blob of DSP code in the ARM side that the ARM will program the DSP with at boot and if the other TMS320 systems are any similar they too have "binary blobs" in there and if so it might be able to extract them from the firmware and use them as black boxes the same way the original firmware does. But of course, then that DSP code cannot be legally reditributed.

SumWon:
Michael,

I don't think you need to buy a Vision:M just so that you can see what chips are inside. Based on the pictures I've seen of a disassembled Vision:M and the Vision I disassembled myself, I can tell you what (off the shelf) chips are inside the Vision:M:

TI TMS320DM320 - Dual Core ARM9/C54xx DSP System On Chip
Spansion S29GL032M - 4Mb flash memory
Infineon HYBL256160AF (x2) - 64Mb RAM
Philips ISP1583 - USB 2.0/ATA (IDE) controller

Unfortunately it appears that there are custom logic chips in the Vision and Vision:M. These will be hard to figure out without Creative's design documents and/or reverse-engineering the current firmware.

As other posters in this thread have indicated, the first step in getting any replacement firmware developed is to reverse-engineer the current firmware to see what it does. I've managed to extract the firmware from the firmware updater and had a quick go at running it through an ARM disassembler. It's going to take a lot of work to figure anything out about how it works...

To get the firmware image, you will need to update the firmware on your player. While the updater is running, it extracts the firmware (a file called NK.BIN) to a folder called C:\CTJbFW. If you're quick, you can copy this file before the updater deletes it (which it does when the update is complete).

HTH

ssjmichael:
Well we'd need some scans too apparently. If you're willing to scan the Vision, that would be helpful. The other reason to have an extra one was for testing purposes so we don't accidently screw up our own players. The plans to buy one have been postponed until we can get some sort of solid footing on whether its even possible to really get this going.

Bagder:
I don't see why it shouldn't be possible.

There are lots of players around using this TMS320 chip, some of them even distribute chunks of source code and there's always reverse engineering you can resort to, should all else fail.

And since we haven't mentioned this so far in this thread, our "guide" to new Rockbox ports:

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

SumWon:
Michael,

I'm still not seeing what you're hoping to achieve by 'scanning' the inside of the player. Once you have the existing firmware and an awareness of the hardware used, there is not much more you can learn from 'scans' (although I can provide you with hires digital photos of both sides of the Vision's board if you think it will help).

The Vision(:M) like most other hard disk based players, has two firmwares: a flash based bootloader, which shouldn't even be considered for modification unless you have sophisticated equipment to reprogram it when (and not if) things go wrong. And a disk based OS which is loaded by the bootloader. Most players (including the Visions) are able to (use the flash-based firmware to) reprogram the disk based OS through the USB port even if the disk has been completely replaced/zeroed.

As Daniel indicated, there's no particular reason why the firmware couldn't be rewritten on these players. They use (largely) off the shelf chips for which there are open-source firmwares available. The original Nomad Jukebox (6Gb) had an encrypted disk based OS, which meant that either the encryption had to be broken, or the bootloader reprogrammed. Which made modifying or replacing the firmware (practically) impossible. Looking at the Vision's firmware, it does not appear to be encrypted in any way.

However, there is a lot of very skilled reverse-engineering work needed before the firmware can be replaced. This will be the stumbling block (if any). I certainly wouldn't buy a player or get my hopes up until fair progress has been made on disassembling/reverse-engineering the current firmware. I'm certainly no expert in this area, but off the top of my head, I can tell you that the very least you'd need to find out, is how the (disk based) firmware's checksum is calculated and verified, and how to find the entry point...

HTH

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