On Wed, Apr 30, 2008 at 02:26:22PM -0700, Trent Piepho wrote: > On Tue, 29 Apr 2008, Hans J. Koch wrote: > > I have an embedded board with a PCA9554 on it. It's an 8-bit IO expander > > similar to the PCF8574 in mainline. One difference is that when reading > > from the inputs, you have to do the following: > > > > - start condition > > - send slave address, R/W=0 > > - send command (0x00 = read input register) > > - issue another start condition (!) > > - send slave address, R/W=1 > > - read data > > - stop condition > > > > Can such a protocol be handled by the i2c subsystem? > > Yes. That is a normal repeated start transaction, and AFAIK exactly what > all the other PCA, and virtually every other i2c chip for that matter, use. > The smbus read byte data function will do this for you.
OK, thanks. I admit, I would be strange if the i2c subsystem didn't support that. > > If you want multiple stops in a single transaction, the i2c subsystem can't > do it, but I wrote a simple patch that allows it. No need for that now, but I'll remember that... Thanks, Hans _______________________________________________ i2c mailing list [email protected] http://lists.lm-sensors.org/mailman/listinfo/i2c
