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This hack will allow user-written software to be run on a JuiceBox media player toy. It works by tricking the built-in picture viewer application to run code contained in a .JBP picture file that starts with a specific 8-byte sequence. Normal operation of the JuiceBox is not affected, other than the 1-out-of-18-quintillion chance of a real picture containing the trigger sequence.
You will need the following items and equipment:
You will need the following items and equipment:
- A JuiceBox, either 2MB or 8MB. (To tell the difference: only 2MB units have a power-on LED, located above and to the right of the REWIND button.) Note that an 8MB unit does not necessarily allow larger programs to be run, the top 6MB normally just goes to waste.
- A SD/MMC card adaptor for the JuiceBox, either the official one that came with the MP3 Starter Kit, or a homemade one as numerous people have built; a SD or MMC card of no more than 512MB capacity; and some way of copying files onto that card from a computer. Basically, you have to be able to use the built-in picture viewer application.
- A soldering iron with a fine tip.
- At least some knowledge of how to USE that soldering iron - I wouldn't recommend this as your first soldering project. You will need to be able to solder pins that are spaced 1/20" apart without bridging them.
- Solder, preferrably of small diameter - I use 0.020" solder for fine work like this.
- Tweezers and/or needle-nose pliers.
- Wire cutters.
- Small Phillips and flat-tip screwdrivers.
- Electrical tape.
- A magnifying glass would be very helpful.
- Modding your JuiceBox to add a serial port is necessary for some Pixecutor programs (such as the one that gives you shell access), but there are still things you can do without a serial port.
- A PIC microcontroller, specifically a PIC12F508-I/SN, programmed with the Pixecutor code found here: http://www.elinux.org/wiki/JuiceBoxPixecutor (try http://moin.elinux.org/wiki/JuiceBoxPixecutor if that site doesn't have the info). This is not something you're likely to be able to do yourself; even if you had a PIC programmer, you probably don't have the adapter needed to handle a SOIC-8 chip (and those aren't exactly cheap). I now sell programmed chips for those of you who aren't equipped to do it yourself. If anybody else out there wants to offer preprogrammed chips at a reasonable price, I'd be happy to link to you.
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Signing UpStep 1Open case, remove foil
Start by removing the four screws in the corners of the back cover. You don't need to remove the screw that holds the battery cover in place.
Carefully separate the two halves of the case - keep in mind that they're still connected together by wires at the bottom edge. (You could disconnect these wires and entirely separate the halves, but that's probably not worth the extra effort.) Make sure you find the little piece of plastic that just flew across the room - it's needed to hold the flip-up screen cover in place.
Position the unit as shown - LCD screen face down, cartridge slot to the right. All subsequent steps will show the unit in this same orientation.
You need to peel away at least part of the shielding foil on the back of the circuit board, starting in the corner between the volume control and headphone jack. Make sure you get the underlying layer of clear plastic, too, not just the copper foil. Make sure there are no slivers of foil left behind that could short something out.
Carefully separate the two halves of the case - keep in mind that they're still connected together by wires at the bottom edge. (You could disconnect these wires and entirely separate the halves, but that's probably not worth the extra effort.) Make sure you find the little piece of plastic that just flew across the room - it's needed to hold the flip-up screen cover in place.
Position the unit as shown - LCD screen face down, cartridge slot to the right. All subsequent steps will show the unit in this same orientation.
You need to peel away at least part of the shielding foil on the back of the circuit board, starting in the corner between the volume control and headphone jack. Make sure you get the underlying layer of clear plastic, too, not just the copper foil. Make sure there are no slivers of foil left behind that could short something out.
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Holding the PIC in reset would indeed allow it to stay out of the way of a JTAG debugger. However, there's no general way to get the JTAG debugger to tri-state its outputs, to get out of the PIC's way. You'd probably have to physically disconnect and reconnect the JTAG pod every time you ran the program.