"The real challenge was how [to] make IR work simultaneously with six remotes," Clarke said. "All six must send out data at different beat frequencies. How it works is that if all six buttons are pressed at the same time, there's a collision. But the receiver knows that because there's a failure. Each remote then retransmits at a different beat frequency. This way, the probability of them all colliding is minimal. It's a guaranteed protocol because we know it's not expandable beyond six."
Generally, IR is a line-of-sight interface. However, the Nytric designers wanted to get a little beyond line-of-sight, giving the signals the ability to bounce off walls and produce reflections.
"Because of the many hardware changes along the way, the software had to be written [with] complete platform independence," says Allen Rego, head of Nytric's software design team. "For this reason, we couldn't have the games compiled. So we looked for an interpreted language, something like a Java. We decided on a scripting language called Lua, which is what all the games are written in."
Lua is an open-source freeware scripting language that needs a low memory footprint compared with Java and other rival languages.
The software team then had to request direct hardware access from National Semiconductor--something National doesn't normally supply to third-party developers.
This access was needed to develop the games. Along the way, the team rewrote some of the graphics libraries and drivers to get hardware access for speed optimizations.
Then, the team members wrote the software to support the late-arriving hardware, including the IR remotes and NOR flash, adding some tricks to squeeze out the best performance.
"It's almost like developing a Web page," Rego said. "You come up with the scripting language, but at a very high level, define an architecture for the game, how you are going to move everything, what animations are going to occur, and so on. Then we wrote all the background software that went into the low-level execution."
The scripting language is byte-code interpreted so that it's cross-platform-compatible. Hence, the platform would be backward-compatible down the road, even if a different processor was employed.
Another device on the board is an octal D-type latch, the SN54LVC573A, from Texas Instruments. Designed for 2.7- to 3.6-volt VCC operation, it has three-state outputs to drive high-capacitive or low-impedance loads, such as buffer registers, I/O ports, bidirectional bus drivers and working registers.
The designers ran into a slight bump in the road in the final stages: A metal top was needed to eliminate potential emissions problems caused by the loader.
The next generation will probably come around 2009. Features could include an HD or BluRay DVD, and a more robust graphics engine. At this point, nothing is set in stone.
Richard Nass is editor in chief of Embedded Systems Design magazine. You can reach him via e-mail at rnass@cmp.com.
