I2C Controller

Hi Andrew,

I have a simple I2C-Slave from an old design, mixing schematic and VHDL design Please check if it's of any use for you. It has been using a 8 MHz clock originally. The I2C connection is intended to use an external buffer for 5V capability, for a 3.3V bus, you can use internal IO of course.

FYI. Don't know if you have the option but SPI is slightly easier to work with.

I'm using a USB controller (FX2LP) that is communicating with the FPGA, but from what I've read the FX2LP doesn't have a SPI interface. It has standard serial pins, but that's not the same, is it? I've never used SPI so I don't know what's involved. When you say easier do you mean more cores are available or is it just a simpler protocol?

Oh, one other thing, I was checking out the opencore design but that seems like its a master only. Has anyone used any of the slave designs on opencores and do they work reliably?

With FX2, an I2C controller is already present while SPI has to be emulated by I/O bit-banging. Thus I2C needs less resources at the uP side and can operate faster. If the FPGA is intended to be configured by the uP through passive serial, you need to create an SPI-like interface anyway and can use it for runtime communication as well.

Thanks for all the help everyone. I spent a little time playing around with a slave I2C core from opencores (http://www.opencores.org/?do=project&who=i2cslave) and much to my delight it worked on the first try! So if anyone needs to do a similar thing check out that core, its super easy to use.

Sorry, a bit late coming to the party.

try this: http://www.grigaitis.eu/?p=18