> The hardware I2C gadget inside the OOPic is used ONLY for oDDELink.
> All other I2C peripherals connect to the local I2C bus the OOPic uses
> to talk to the EEPROM. This is bit-banged and pretty slow.
This is probably philosophy but do people use oDDELink enough to
justify essentially eliminating the hardware I2C gadget?
> You compass (and every other device you want to interface with I2C)
> will connect to this low speed, bit-banged, I2C bus. Be careful about
> capacitive loading (long cables).
>
> Your PIC will have to operate as an I2C slave because the OOPic is
> always the bus master. For this to have a chance of working, you
> should probably write the PIC serial IO routines as fully interrupt
> driven with a large circular buffer (not that the PIC has very much
> RAM!). The I2C gadget is normally coded as an interrupt driven state
> machine. Code is available at Microchip and on the web.
>
> All the PIC mainline code has to do is grab the sentences from the
> serial buffer, do some interpretation and post the results to an area
> of memory that the I2C code can grab.
>
> Frankly, I wouldn't do it this way. I2C is hard to implement, much
> harder than SPI. I would spend a little time looking at the OOPic
> oSPI object and the PIC datasheet and see if SPI would be easier.
I am getting ready to interface to a bunch of I2C devices and just
need to use I2C. It seems so silly to make the hardware I2C widget in
the PIC unusable to talk to other sensor devices. This is looking like
it might turn out to be a real pain. I am just wondering about the
logic or whether Savage Innovations is considering making a change.
--
73 de Brian, WB6RQN
Brian Lloyd - brian HYPHEN wb6rqn AT lloyd DOT com
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