#define _PAGE_ Rockbox in Flash - FAQ and User Manual #include "head.t"

by Jörg Hohensohn aka [IDC]Dragon

1. Introduction
2. Method
3. Risks
4. Requirements
5. Flashing procedure
6. Bringing in a current or personal build of Rockbox
7. Known issues and limitations
8. Movies and images

1. Introduction

Flashing in the sense used here and elsewhere in regard to Rockbox means reprogramming the flash memory of the Archos unit. Flash memory (sometimes called "Flash ROM") is a type of nonvolatile memory that can be erased and reprogrammed in-circuit. It is a variation of electrically erasable programmable read-only memory (EEPROM).

When you bought your Archos, it came with the Archos firmware flashed. Now, you can replace the built-in software with Rockbox.

Terminology used in the following:
Firmware means the flash ROM content as a whole.
Image means one operating software started from there.

By reprogramming the firmware, we can boot much faster. Archos has a pathetic boot loader, versus the boot time for Rockbox is much faster than the disk spinup, in fact it has to wait for the disk. Your boot time will be as quick as a disk spinup (e.g. 4 seconds from powerup until resuming playback).

2. Method

The replaced firmware will host a bootloader and 2 images. This possible by compression. The first is the "permanent" backup, not to be changed any more. The second is the default one to be started, the first is only used when you hold the F1 key (will be Menu for recorders) during start. Like supplied here, the first image is the original Archos firmware, the second is a current build of Rockbox. This second image is meant to be reprogrammed, it can contain anything you like, if you prefer, you can program the Archos firmware to there, too.

There are two programming tools supplied:

More technical details will be provided in the future, as well as non-user tools. There's an authoring tool which composed the firmware file with the bootloader and the 2 images, the bootloader project, the plugin sources, and the tools for the UART boot feature: a monitor program for the box and a PC tool to drive it. Feel free to review the sources for all of it, but be careful when fooling around with powerful toys!

3. Risks

Well, is it dangerous? Yes, certainly, like programming a mainboard BIOS, CD/DVD drive firmware, mobile phone, etc. If the power fails, your chip breaks while programming or most of all the programming software malfunctions, you'll have a dead box. We take no responsibility of any kind, you do that at your own risk. However, we tried as carefully as possible to bulletproof this code. The new firmware file is completely read before it starts programming, there are a lot of sanity checks. If any fails, it will not program. Before releasing this, we have checked the flow with exactly these files supplied here, starting from the original firmware in flash. It worked reliably, there's no reason why such low level code should behave different on your box.

There's one ultimate safety net to bring back boxes with even completely garbled flash content: the UART boot mod, which in turn requires the serial mod. It can bring the dead back to life, with that it's possible to reflash independently from the outside, even if the flash is completely erased. It has been used that during development, else Rockbox in flash wouldn't have been possible. Extensive development effort went into the exploitation of the UART boot mod. Mechanically adept users with good soldering skills can easily perform these mods. Others may feel uncomfortable using the first tool (firmware_flash.rock) for reflashing the firmware.

To comfort you a bit again: If you are starting with a known-good image, you are unlikely to experience problems. The flash tools have been stable for quite a while. Several users have used them extensively, even flashing while playing! Although it worked, it's not the recommended method. ;-)"

About the safety of operation: Since we have dual boot, you're not giving up the Archos firmware. It's still there when you hold F1 during startup. So even if Rockbox from flash is not 100% stable for everyone, you can still use the box, reflash the second image with an updated Rockbox copy, etc.

The flash chip being used by Archos is specified for 100,000 cycles (in words: one hundred thousand), so you don't need to worry about that wearing out.

4. Requirements

You need two things:

5. Flashing procedure

Short explanation: copy the firmware_*.bin files for your model from the distribution to the root directory of your box, then run the "firmware_flash.rock" plugin. Long version, step by step procedure:

6. Bringing in a current or personal build of Rockbox

Short explanation: very easy, just play a .ucl file like "rockbox.ucl" from the download or build. Long version:

The second image is the working copy, the "rockbox_flash.rock" plugin from this package reprograms it. The plugins needs to be consistant with the Rockbox plugin API version, otherwise it will detect mismatch and won't run.

It requires an exotic input, a UCL-compressed image, because that's the internal format. UCL is a nice open-source compression library. The decompression is very fast and less than a page of C-code. The efficiency is even better than Zip with maximum compression, cooks it down to about 58% of the original size. For details on UCL, see: www.oberhumer.com/opensource/ucl/

Linux users will have to download it from there and compile it, for Win32 and Cygwin the executables are in the packages. The sample program from that download is called "uclpack". We'll use that to compress "rockbox.bin" which is the result of the compilation. This is a part of the build process meanwhile. If you compile Rockbox yourself, you should copy uclpack to a directory which is in the path, we recommend placing it in the same dir as SH compiler.

Don't flash any "old" builds which don't have the latest coldstart ability. They won't boot. These instructions refer to builds from cvs state 2003-07-10 on.

Here are the steps:

If you like or have to, you can also flash the Archos image as the second one, e.g. in case Rockbox from flash doesn't work for you. This way you keep the dual bootloader and you can easily try different later. You can download UCLs for the latest firmware here.

7. Restoring the original firmware

If you'd like to revert to the original firmware, you can do like you did when you flashed Rockbox for the first time (section 5), but copy and rename your backup to be "firmware_rec.bin" on the box this time. Keep the Rockbox copy and the plugins of this package for that job, because that's the one it was tested with.

8. Known issues and limitations

Latest Rockbox now has a charging screen, but it is in an early stage. You'll get it when the unit is off and you plug in the charger. The Rockbox charging algorithm is first measuring the battery voltage for about 40 seconds, after that it only starts charging when the capacity is below 85%. You can use the Archos charging (which always tops off) by holding F1 while plugging in. Some FM users reported charging problems even with F1, they had to revert to the original flash content.

If the plugin API is changed, new builds may render the plugins incompatible. When updating, make sure you grab those too, and rolo into the new version before flashing it.

There are two variants of how the boxes starts, therefore the normal and the _norom firmware files. The vast majority of the Player/Recorder/FM all have the same boot ROM content, differentiation comes later by flash content. Rockbox identifies this boot ROM with a CRC value of 0x222F in the hardware info screen. Some recorders have the boot ROM disabled (it might be unprogrammed) and start directly from a flash mirror at address zero. They need the new _norom firmware, it has a slightly different bootloader. Without a boot ROM there is no UART boot safety net. To compensate for that as much as possible the MiniMon monitor is included, it starts with F3+On. Using that the box can be reprogrammed via serial if the first ~2000 bytes of the flash are OK.

8. Movies and images

Jörg's AVI movie (1.5MB) rockbox_flash_boot.avi showing his unit booting Rockbox from flash.

Roland's screendump from the movie:
#include "foot.t"