This is a serial AVR programmer, even though it connects to the computer's parallel port. See the Programers page for more.
This programmer is not slow. Cable length may be something to watch. I used a 6 foot cable with no problems, but I have an older motherboard
in the test machine, so it may have higher voltage outputs. Most of the other parallel port programmers here may have better reliability
than this one, since they are buffered in some way.
Schematic Diagram
Parts
R1-R4 470 Ohm 5% 1/8W resistor
X1 DB25P solder cup connector
Not shown
DB25 headshell
6 or 10 conductor ribbon cable
6 or 10 conductor ribbon connector
Notes
The target microcontroller must provide it's own power.
The target power supply voltage must be the same as that of the parallel port.
The parallel port forms an SPI serial interface to the chip.
Assembly
This is the easiest of all of the programmers. No perfboard is required, since all connections to the port are
either direct or through a single series resistor. I haven't tried it, but general experience suggests that it
would be foolish to omit the resistors.
The thing that looks like a wire tie is. The cable clamp on the 25-pin connector is too large to clamp the cable,
so I put a wire tie on to give it something to pull against.
