Logicport overview
posted Jun 24th 2008 4:30am by Eliot Phillipsfiled under: misc hacks
As promised earlier, the Near Future Laboratory has published an overview of the Logicport Logic Analyzer. They’re using the Playstation 2 analysis as an example. The Logicport uses “interpreters” to define protocols. It has I2C/TWI, SPI, RS232, and CAN 2.0A/2.0B, but you can build your own interpreter based on these. You can specify bit order and the format you want the data in. Slave interpreters can be used for specific tasks: with the PS2 they were used to just show the fifth byte, which is the actual button press.
“Triggers” are used to signal specific activity. On the PS2, one was attached to the falling signal on the slave select line. This event means the master is about to start sending data.
The final area worth exploring is “measurements”. These can be frequency or arbitrary time intervals between events. The Logicport has multiple ground connections to eliminate noise from the signal and you’ll have to play with sample rate and logic level to get things running smooth. It’s nice to see how-tos written from the perspective of someone just getting started with the tool.
Using this would have been a lot easier than turning PICs into SPI-to-serial converters, which is what we did to research our ps2 interface guide: http://www.curiousinventor.com/guides/ps2
For people looking to emulate a PS2 controller, we recorded the first 600 or so bytes of handshaking between a PS2 and various controllers (dual shock, guitar hero, Chinese knock off–worked about the same as the official DS). The recordings are available in a spreadsheet at the bottom of the guide, as well as a circuit diagram and source code. It’s surprising how much handshaking goes on considering that only a few commands are necessary to setup a controller to use all the analog values (including button pressures) and vibration motors.
Posted at 8:12 am on Jun 24th, 2008 by CuriousInventor