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SSP on the BitsyXb
The BitsyXb makes use of the three PXA270 synchronous serial ports as illustrated in the
following diagram.
PXA270
Touch
panel
controller
ATMega
ADSmartIO
SSP3
SSP1
SSP2
J3
J16
The BitsyXb uses PXA270 SSP1 to communicate with the ADSmartIO controller. The signals for
SSP1 come out to J16 for factory programming, but are not intended for application use.
The BitsyXb uses SSP2 to communicate with the touch panel controller. Applications can use
SSP3 for control of external peripherals.
The BitsyXb generates the SSP bit clocks from the on-chip 13 MHz clock. It does not support an
external clock input.
Electrical specifications for SSP3 are listed in section 6.3.9. Consult the operating system
references for details about how to use the SSP bus for external devices.
4.5.4
I
2
C Bus Master
I
2
C (Inter-IC) Bus is a multi-master, "two-wire" synchronous serial bus developed by Philips for
communications between integrated circuits (ICs). The bus master addresses devices using the
data line and provides a synchronous clock for reading and writing devices. Client devices
respond only when queried by the master device. Philips has developed many I
2
C devices, but
other organizations have adopted I
2
C as a convenient means for addressing peripherals in a
system.
