I know this topic probably needs a stake through its heart, but here is my guesstimate of what would be involved in making a HDMI --> VGA adapter. This is based on the the absence of a cheap single chip solution that can be dropped onto a small PCB. That would be a nice simple little project.
Note that its NOT just a pcb with a few wires soldered on we are talking about here. The HDMI spec uses high speed differential serial data streams as well as a i2c control bus to talk to the display device. VGA needs 3 analog colour signals and H and V sync signals all derived from the HDMI signals. VGA also has a serial control bus - which probably needs translating. HDMI allows +5 at 50mA to power the converter circuit, which should be sufficient.
A possible design would look like -
o HDMI socket with termination for the diff signals
o VGA socket with possibly some termination
o 68-100 pin tqfp PLD (Atmel or Xylinx or Lattice) to do all the serial decoding and drive the DACs and make the V sync H sync signals
o Triple video DAC like - http://www.analog.com/en/digit.....oduct.html
- cheap, low power and looks like it can drive the VGA cable directly
o small microcontroller (PIC or Atmel) to detect the VGA monitor connected and talk to HDMI and control the operation of the PLD. Also, this micro can probably reflash the PLD firmware if required. Using a microcontroller would help make this easier as an OS project.
The parts cost would be maybe $15 - $20 each for a few hundred.
This is not a trivial project. Lots of pdf reading of HDMI and VGA specs would be required. By the time it is done the cost difference between a cheap VGA monitor and a HDMI monitor may be less than the adapter. On the other hand it may be a nice project for some engineering students who wish to learn about electronics and video standards.