Electronic – Possibility of SMBus/PMBus device with I2C Master

If you take some time and poke around Wikipedia you'll find a page describing the differences between I2C and SMBus; the one that's probably getting you is the packet checksumming or PEC; this is not required for I2C transfers but SMBus devices want it. It's not difficult to calculate and append to the transfer, so you might want to start there.

Obviously if you have a logic analyzer it'd be prudent to throw that on first and see if that really is what's causing your troubles before going to the effort of writing the code. :-) You can also probably lift the PEC generation code from the linux kernel, as it has I2C and SMBus drivers and the places like the Linux Cross Reference are excellent at helping you find out where the code you're interested is hiding.

Good luck!

The meat-and-potatoes of the licensing issue is as follows: (I am not a lawyer)

• Power-One holds a patent that covers their Z-One point-of load converter: U.S. Patent No. 7,000,125
• Power-One sued Artesyn over a point-of-load product that was never released to the marketplace, based around PMBus
• Patent 7,000,125 was interpreted to cover the following:
  • A digital power control system for programming, controlling, and monitoring an array of Point of Load regulators using a data bus for communication with and control of the Point of Load regulators, where:
  • Point of Load Regulator is a dc-dc switching voltage regulator designed to receive power from a voltage bus on a printed circuit board, and adapted to power a portion of the devices on the board and to be placed near the one or more devices being powered as part of a distributed board-level power system.
• Artesyn lost and had to pay $100 (one hundred dollars)
• Power-One maintains that any POL converter with digital control and/or communication needs a license

Some quick searches show me that several companies have entered into licensing agreements with Power-One concerning digital power:

• Microchip
• International Rectifier
• Powervation
• TDK-Lambda
• CUI
• ZMD AG
• Intersil / Zilker Labs
• Texas Instruments

(etc.)

SO ... if you're using an off-the-shelf PMBus controller in a POL application, check that the manufacturer has a license. If you're spinning your own custom solution with a microcontroller, I suggest using a micro for which the manufacturer has a license.

That, and call a patent lawyer. Seriously. This patent business is exceedingly nasty.