Hi
I'm trying to interface an external slave device to an IRIS mote using the MOSI
and SCK lines on the 51-pin connector and a GPIO pin (PortC5) configured as the
slave select (my external device has only 1 data line for input so MISO is
unused).
I used an oscilloscope to look at the SCK and the MOSI lines and I see the
clock
signals being generated (3 8-clock waveforms for the 3 bytes that I'm trying to
write). However, at the same time, the MOSI line stays flat. Just FYI, the MOSI
line is always low while the MISO line is always high. Also, the pattern stays
the same whether or not I actually connect the external device. Also, the radio
stack is not used in my program so there should be no conflicts (other than the
physical wires routed from the SPI lines to the radio chip)
I am using the Resource and SpiByte interfaces from the Atm128SpiC component as
follows.
event void Timer.fired(){
call SpiResource.request();
}
event void SpiResource.granted(){
post writeSlave();
}
void task writeSlave(){
uint8_t discard;
call SlaveSelect.clr(); //this is portC5
discard = call SpiByte.write(0xff);
discard = call SpiByte.write(counter);
discard = call SpiByte.write(0);
call SlaveSelect.set();
call SpiResource.release();
counter = counter + 32;
}
Does anyone have any insights on why this does not work?
Thanks
Sandip
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