ZBasic System Library
103
ZBasic Microcontrollers
Type
Subroutine
Invocation
DefineSPI(clkPin, mosiPin, misoPin)
Parameter
Method
Type
Description
clkPin
ByVal
Byte
The pin to serve as the SPI clock signal (output).
mosiPin
ByVal
Byte
The pin to serve as the SPI MOSI signal (output).
misoPin
ByVal
Byte
The pin to serve as the SPI MISO signal (input).
Discussion
This subroutine is used to specify the clock and data pins to use for the software driven SPI
implementation (sometimes known as a “bit banged” implementation). If the flags parameter to the
OpenSPI subroutine requests software SPI, OpenSPI will initialize the specified pins (clkPin and
mosiPin as output, misoPin as input) and set clkPin to the idle state specified by the flags
parameter to OpenSPI. If software SPI is not requested, OpenSPI will initialize the hardware SPI
controller according to the flags parameter to OpenSPI.
It is important to be aware that the pin values set by DefineSPI are used by both the OpenSPI and
SPICmd routines. This fact requires some extra attention if your application uses multiple SPI channels
and two or more of them use the software-driven implementation. In such cases, you must ensure that
the SPI pins have been correctly set by a prior call to DefineSPI before each call to OpenSPI and
SPICmd. If your application uses just one channel with software SPI, a single call to DefineSPI will
suffice and if it does not use software SPI at all then DefineSPI needn’t be called either.
Compatibility
This subroutine is not supported in BasicX mode nor it is supported on any VM mode ZX device.
See Also
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