yup! I'm using webbot, so I've tried:
And neither work. I've tried to change which pin is SS, from B4 to B3, and nothing (and I followed internet advice that said to make sure B4 is output anyway). The kicker is that I can set B0 all I want -- it has an LED on it and it goes high and low to indicate which Byte I'm sending over SPI. I can also SEND and RECEIVE stuff over SPI: the slave device turns its LED on when it receives 0x01 and off when it receives 0x00, and that's been happening, as long as I hardwire the SS pin of the slave to ground.
So I'm stumped at this point. I have absolutely no idea why I can't drive the SS pin low. My only guess is that the SS pin on the slave is floating somehow and driving the SS pin of the master to a high state always. But I've tried a pull-up resistor and also, just for fun, a pull-down. Both 10K. Maybe the circuit just hates me :-P
I think I'm just going to use an ARM and avoid inter uC communications altogether, but I'd still love to know what's wrong!