Getting X-Windows and VGA out of an iPaq or Stargate board

Yesterday I took a tutorial on building a wearable computer from the Intel-based Stargate board. Both the Stargate and for that matter the iPaq have a good form-factor for a Tin-Lizzy-style wearable (small, low power and have USB-Host for a one-handed keyboard) except for the big problem that they don’t have VGA-out to drive a head-up display. Kent Lyons has developed a nice hack to get around this limitation. (Technical summary follows.)

The hardware Kent’s using is IO Data’s Compact-Flash XGA card. Compact Flash doesn’t have enough pins to memory-map, so the CFXGA card uses the BLT interface to send just the pixels that change. (The card is designed for giving PowerPoint presentations from your handheld so they’re not worried about fast-changing scenes.) Kent leverages this by using his own modified X server that can use the BLT interface. It’s only 640×480 at 16 bpp, but it’s enough for text and simple interfaces on a head-up display. There’s code and a brief how-to at Kent’s website, as well as an email address where you can bug him to add more detail :).