.\" man page for Munts Technologies Linux Simple I/O Library
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.TH libspi 2 "21 December 2018" "version 1" "Linux Simple I/O Library"
.SH NAME
.B libspi
\-\- Linux Simple I/O Library: SPI Module
.SH SYNOPSIS
.nf
.B #include <libsimpleio/libspi.h>

.BI "void SPI_open(const char *" name ", int32_t " mode ", int32_t " wordsize ","
.BI "  int32_t " speed ", int32_t *" fd ", int32_t *" error ");"

.BI "void SPI_close(int32_t " fd ", int32_t *" error ");"

.BI "void SPI_transaction(int32_t " spifd ", int32_t " csfd ", void *" cmd ","
.BI "  int32_t " cmdlen ", int32_t " delayus ", void *" resp ", int32_t " resplen ","
.BI "  int32_t *" error ");"

.fi
Link with
.BR -lsimpleio .
.SH DESCRIPTION
.nh
All functions return either
.B 0
(upon success) or an
.B errno
value (upon failure) in
.IR *error .
.PP
.B SPI_open()
opens an SPI slave device.  The device name,
.BR /dev/spidevx.x ,
must be passed in the
.IR name
parameter. The
.I mode
parameter specifies the SPI bus transfer mode,
.BR 0 " to " 3 .
The
.I wordsize
parameter specifies the SPI bus transfer unit size, usually
.BR 8 ", " 16 ", or " 32 " bits."
Some SPI controllers only allow 8-bit transfers.
The
.I speed
parameter specifies the SPI bus transfer speed in bits per second.
Upon success, a file descriptor for the
SPI slave device is returned in
.IR *fd .
.PP
.B SPI_close()
closes a previously opened SPI slave device.
.PP
.B SPI_transaction()
performs a single SPI bus transaction, with optional transmit and receive
phases. Either the address of a command message and its length must be passed in the
.IR cmd " and " cmdlen
parameters, or
.BR NULL " and " 0
for a receive only transaction.  The
.I delayus
parameter indicates the time in microseconds between the transmit and receive phases.  It
should be set long enough for the SPI slave device to execute the command and generate its
response.
Either the address of a receive buffer and its size must be passed in the
.IR resp " and " resplen
parameters, or
.BR NULL " and " 0
for a transmit only transaction.  The
.IR csfd
parameter should be set to
.BR SPI_CS_AUTO
to use the hardware controlled slave chip select signal or set to the open file descriptor
for a GPIO pin to use for the software controlled slave chip select signal.
.SH SEE ALSO
.BR libsimpleio "(2), " libadc "(2), " libdac "(2), " libevent "(2), " libgpio "(2),"
.br
.BR libhidraw "(2), " libi2c "(2), " libipv4 "(2), " liblinux "(2), " liblinx "(2),"
.br
.BR libpwm "(2), " libserial "(2), " libstream "(2), " libwatchdog "(2)"
.SH AUTHOR
Philip Munts dba Munts Technologies.