At 17:05 13.03.97 +0000, you wrote:
>Wolfram,
>
>yeah i remmember that thread about switching to SPI mode -
>
>but i'm confused - are we still using the designated I2C SDA/SCL
>pins ? so how can you switch to SPI mode?
>or are we talking about using the SPI module to do this (i.e.
>different pins) ?
>
>nishant
>

Nishant,

SDA (I2C) equals SDI (SPI). So you should connect SDI and SDO of the
SPI module, to be able to transmit and receive on the same line. But
then you have to take a lot of care to correctly configure and
reconfigure the data-direction bit for SDO to avoid collissions
between SDO and a slave device, transmitting data.

I have not tried this setup, I only think, that it might be possible
to be done.
But if you think of all the software-efforts and also the restrictions
and compromises of this SPI-driven solution, it might be easier and better,
to have an all-software solution for I2C master devices.

The best solution could be, to use the 17C75x, as it contains I2C master
and also 10bit A/D. And has a lot more features.

regards,

Wolfram


+-----------------------------------------------------+
| Wolfram Liebchen                                    |
| Forschungsinstitut fŸr Optik, TŸbingen, Deutschland |
| mailto:liebchen@ffo.fgan.de                         |
+-----------------------------------------------------+