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Schematics

The schematic is very simple. There are very few components. The main component is a PIC microcontroller which needs to be programmed (which is also easy to make)

The unilink connector is quite complicated. You will need to get a cable from a sony retailer (very expensive) or from a car radio installer. They sometime have some damaged unilink cables that you can get and cut to connect to the pic board. The JVC KS-U15K adapter has one end which is similar to the unilink connector and is pretty cheap (around ~$10 US). It should also work.

You need a generic board, place the components and connect the few needed connections. The original schematic is on the original Gnunilink project website.

The serial communication between pic and archos is totally handled by software. The pic uart is not used because I don't have a 16f628 and I don't think it is possible to perform an open collector communication with it.

You don't need to use the max202. As the software uart can invert the serial pin, it is possible to log the data with a direct rs232 cable connection to the pic. In this case, you will have to swap the SERIAL_0 and SERIAL_1 in the source code (but the archos communication won't work anymore). (please look at Faq for more info)

You can choose any pic PIO pin to communicate. (I think I use port RB2 on pin 8) It is defined by the SERIAL_PORT define in GNUnilink.asm.

Make a direct connection. Then just add a 10k pull up resistor to the PIC vcc.

If you don't have a pic programmer, I suggest that you implement an in situ programmer. (see the Schematics)

Troubleshooting

What can you do if it doesn't work.

• when you connect, does anything happen on the HU?
  • No: Check that your pic is working by programming a blinking pin hex file. Use a multimeter to see if the pin is blinking. Try an hex from there. Make sure that when you program, you use the external oscilator (HS mode)
  • Yes: your pic seems to be doing something but it is wrong.
    • First check that you have the latest version from the subversion repository.
    • Check that you have good frequency settings inside the GNUnilink.asm file and recompile.
    • If it still doesn't work, you will have to log with a serial line and the python logger then post the results in the forum.

Auto power on

It is a MUST HAVE feature. When you start your car, the archos is started automatically.

To do that I moded my player because it cannot be flashed. Flashed recorders can start automatically with power applied.

The gnunilink does have 2 control signals: one for controling the power through a power transistor, one for simulating the 'ON' button push.

For the archos players, a hardware mod is needed. I connected the On button wire to one of the line in connector wire. Some photos in Archos

The other end is directly connected to one of the pic pins (see the Schematics)

more to come...

Contact me in the forum for more details on the mod.

Recompiling the GNUnilink source

The source files are compiled with 'gnu pic utils' (gputils). gputils works on most platforms.

Personally, I recompiled gputils under cygwin under windows. To do that,

• download and install cygwin. In the setup.exe you need to check some packages to be installed: gcc, gmake (maybe some others are needed).
• download the gputils sources,
• type ./configure
• type make install

There is also a native windows version that I haven't tested.

To test if it works, just type 'gpasm'.

Once gpasm works, download the GNUnilink source from here or from the Subversion repository.

Once in the GNUnilink directory, just type gpasm GNUnilink.asm. You will obtain the GNUnilink.hex that you can program into the pic with IcProg.

It is normal that you have lots of messages like Register in operand not in bank 0. Ensure bank bits are correct Other messages are not normal...