/
spi.go
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/
spi.go
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package bbio
// #include <linux/spi/spidev.h>
// #include <sys/ioctl.h>
import "C"
import (
"fmt"
"os"
"syscall"
"unsafe"
)
const (
SPI_CPHA uint8 = 0x01 /* clock phase */
SPI_CPOL uint8 = 0x02 /* clock polarity */
SPI_CS_HIGH uint8 = 0x04 /* chipselect active high? */
SPI_LSB_FIRST uint8 = 0x08 /* per-word bits-on-wire */
SPI_3WIRE uint8 = 0x10 /* SI/SO signals shared */
SPI_LOOP uint8 = 0x20 /* loopback mode */
)
// not used yet
const (
SPI_NO_CS = 0x40 /* 1 dev/bus, no chipselect */
SPI_READY = 0x80 /* slave pulls low to pause */
SPI_TX_DUAL = 0x100 /* transmit with 2 wires */
SPI_TX_QUAD = 0x200 /* transmit with 4 wires */
SPI_RX_DUAL = 0x400 /* receive with 2 wires */
SPI_RX_QUAD = 0x800 /* receive with 4 wires */
)
// SPI mode as two bit pattern of
// Clock Polarity and Phase [CPOL|CPHA]
// min: 0b00 = 0 max: 0b11 = 3
type SPIMode uint8
const (
SPI_MODE_0 SPIMode = 0 /* (original MicroWire) */
SPI_MODE_1 SPIMode = SPIMode(SPI_CPHA)
SPI_MODE_2 SPIMode = SPIMode(SPI_CPOL)
SPI_MODE_3 SPIMode = SPIMode(SPI_CPOL | SPI_CPHA)
)
type SPI struct {
file *os.File /* open file descriptor: /dev/spi-X.Y */
mode uint8 /* current SPI mode */
bitsPerWord uint8 /* current SPI bits per word setting */
maxSpeedHz uint32 /* current SPI max speed setting in Hz */
}
// NewSPI returns a new SPI object that is connected to the
// specified SPI device interface.
//
// NewSPI(X,Y) will open /dev/spidev-X.Y
//
// SPI is an object type that allows SPI transactions
// on hosts running the Linux kernel. The host kernel must have SPI
// support and SPI device interface support.
// All of these can be either built-in to the kernel, or loaded from modules.
//
// Because the SPI device interface is opened R/W, users of this
// module usually must have root permissions.
func NewSPI(bus, device int) (*SPI, error) {
deviceTreeName := fmt.Sprintf("ADAFRUIT-SPI%d", bus)
err := LoadDeviceTree(deviceTreeName)
if err != nil {
return nil, err
}
spi := new(SPI)
path := fmt.Sprintf("/dev/spidev%d.%d", bus+1, device)
spi.file, err = os.OpenFile(path, os.O_RDWR, 0)
if err != nil {
return nil, err
}
r, _, err := syscall.Syscall(syscall.SYS_IOCTL, spi.file.Fd(), C.SPI_IOC_RD_MODE, uintptr(unsafe.Pointer(&spi.mode)))
if r != 0 {
return nil, err
}
r, _, err = syscall.Syscall(syscall.SYS_IOCTL, spi.file.Fd(), C.SPI_IOC_RD_BITS_PER_WORD, uintptr(unsafe.Pointer(&spi.bitsPerWord)))
if r != 0 {
return nil, err
}
r, _, err = syscall.Syscall(syscall.SYS_IOCTL, spi.file.Fd(), C.SPI_IOC_RD_MAX_SPEED_HZ, uintptr(unsafe.Pointer(&spi.maxSpeedHz)))
if r != 0 {
return nil, err
}
return spi, nil
}
// Read len(data) bytes from SPI device.
func (spi *SPI) Read(data []byte) (n int, err error) {
return spi.file.Read(data)
}
// Write data to SPI device.
func (spi *SPI) Write(data []byte) (n int, err error) {
return spi.file.Write(data)
}
type spi_ioc_transfer struct {
tx_buf uintptr
rx_buf uintptr
len uint32
speed_hz uint32
delay_usecs uint16
bits_per_word uint8
cs_change uint8
pad uint32
}
// Xfer performs a SPI transaction.
// CS will be released and reactivated between blocks.
// delay specifies delay in usec between blocks.
func (spi *SPI) Xfer(txBuf []byte, delay_usecs uint16) (rxBuf []byte, err error) {
length := len(txBuf)
rxBuf = make([]byte, length)
xfer := make([]spi_ioc_transfer, length)
for i := range xfer {
xfer[i].tx_buf = uintptr(unsafe.Pointer(&txBuf[i]))
xfer[i].rx_buf = uintptr(unsafe.Pointer(&rxBuf[i]))
xfer[i].len = 1
xfer[i].delay_usecs = delay_usecs
}
SPI_IOC_MESSAGE := C._IOC_WRITE<<C._IOC_DIRSHIFT | C.SPI_IOC_MAGIC<<C._IOC_TYPESHIFT | length<<C._IOC_SIZESHIFT
r, _, err := syscall.Syscall(syscall.SYS_IOCTL, spi.file.Fd(), uintptr(SPI_IOC_MESSAGE), uintptr(unsafe.Pointer(&xfer[0])))
if r != 0 {
return nil, err
}
// WA:
// in CS_HIGH mode CS isn't pulled to low after transfer, but after read
// reading 0 bytes doesnt matter but brings cs down
syscall.Syscall(syscall.SYS_READ, spi.file.Fd(), uintptr(unsafe.Pointer(&rxBuf[0])), 0)
return rxBuf, nil
}
// Xfer2 performs a SPI transaction.
// CS will be held active between blocks.
func (spi *SPI) Xfer2(txBuf []byte, delay_usecs uint16) (rxBuf []byte, err error) {
length := len(txBuf)
rxBuf = make([]byte, length)
xfer := spi_ioc_transfer{
tx_buf: uintptr(unsafe.Pointer(&txBuf[0])),
rx_buf: uintptr(unsafe.Pointer(&rxBuf[0])),
len: uint32(length),
}
SPI_IOC_MESSAGE := C._IOC_WRITE<<C._IOC_DIRSHIFT | C.SPI_IOC_MAGIC<<C._IOC_TYPESHIFT | 1<<C._IOC_SIZESHIFT
r, _, err := syscall.Syscall(syscall.SYS_IOCTL, spi.file.Fd(), uintptr(SPI_IOC_MESSAGE), uintptr(unsafe.Pointer(&xfer)))
if r != 0 {
return nil, err
}
// WA:
// in CS_HIGH mode CS isn't pulled to low after transfer, but after read
// reading 0 bytes doesnt matter but brings cs down
syscall.Syscall(syscall.SYS_READ, spi.file.Fd(), uintptr(unsafe.Pointer(&rxBuf[0])), 0)
return rxBuf, nil
}
// Disconnects the object from the interface.
func (spi *SPI) Close() error {
return spi.file.Close()
}
func (spi *SPI) Mode() SPIMode {
return SPIMode(spi.mode) & SPI_MODE_3
}
func (spi *SPI) SetMode(mode SPIMode) error {
newMode := (spi.mode &^ uint8(SPI_MODE_3)) | uint8(mode)
err := spi.setModeInt(newMode)
if err == nil {
spi.mode = newMode
}
return err
}
// CS active high
func (spi *SPI) CSHigh() bool {
return spi.mode&SPI_CS_HIGH != 0
}
// CS active high
func (spi *SPI) SetCSHigh(csHigh bool) error {
return spi.setModeFlag(csHigh, SPI_CS_HIGH)
}
func (spi *SPI) LSBFirst() bool {
return spi.mode&SPI_LSB_FIRST != 0
}
func (spi *SPI) SetLSBFirst(lsbFirst bool) error {
return spi.setModeFlag(lsbFirst, SPI_LSB_FIRST)
}
func (spi *SPI) ThreeWire() bool {
return spi.mode&SPI_3WIRE != 0
}
func (spi *SPI) SetThreeWire(threeWire bool) error {
return spi.setModeFlag(threeWire, SPI_3WIRE)
}
// Loop returns the loopback configuration.
func (spi *SPI) Loop() bool {
return spi.mode&SPI_3WIRE != 0
}
// SetLoop sets the loopback configuration.
func (spi *SPI) SetLoop(loop bool) error {
return spi.setModeFlag(loop, SPI_LOOP)
}
func (spi *SPI) BitsPerWord() uint8 {
return spi.bitsPerWord
}
func (spi *SPI) SetBitsPerWord(bits uint8) error {
if bits < 8 || bits > 16 {
return fmt.Errorf("SPI bits per word %d outside of valid range 8 to 16", bits)
}
r, _, err := syscall.Syscall(syscall.SYS_IOCTL, spi.file.Fd(), C.SPI_IOC_WR_BITS_PER_WORD, uintptr(unsafe.Pointer(&bits)))
if r != 0 {
return err
}
var test uint8
r, _, err = syscall.Syscall(syscall.SYS_IOCTL, spi.file.Fd(), C.SPI_IOC_RD_BITS_PER_WORD, uintptr(unsafe.Pointer(&test)))
if r != 0 {
return err
}
if test == bits {
spi.bitsPerWord = bits
return nil
} else {
return fmt.Errorf("Could not set SPI bits per word %d", bits)
}
}
func (spi *SPI) MaxSpeedHz() uint32 {
return spi.maxSpeedHz
}
func (spi *SPI) SetMaxSpeedHz(maxSpeedHz uint32) error {
r, _, err := syscall.Syscall(syscall.SYS_IOCTL, spi.file.Fd(), C.SPI_IOC_WR_MAX_SPEED_HZ, uintptr(unsafe.Pointer(&maxSpeedHz)))
if r != 0 {
return err
}
var test uint32
r, _, err = syscall.Syscall(syscall.SYS_IOCTL, spi.file.Fd(), C.SPI_IOC_RD_MAX_SPEED_HZ, uintptr(unsafe.Pointer(&test)))
if r != 0 {
return err
}
if test == maxSpeedHz {
spi.maxSpeedHz = maxSpeedHz
return nil
} else {
return fmt.Errorf("Could not set SPI max speed in hz %d", maxSpeedHz)
}
}
func (spi *SPI) setModeFlag(flag bool, mask uint8) error {
newMode := spi.mode
if flag {
newMode |= mask
} else {
newMode &= ^mask
}
err := spi.setModeInt(newMode)
if err == nil {
spi.mode = newMode
}
return err
}
func (spi *SPI) setModeInt(mode uint8) error {
r, _, err := syscall.Syscall(syscall.SYS_IOCTL, spi.file.Fd(), C.SPI_IOC_WR_MODE, uintptr(unsafe.Pointer(&mode)))
if r != 0 {
return err
}
var test uint8
r, _, err = syscall.Syscall(syscall.SYS_IOCTL, spi.file.Fd(), C.SPI_IOC_RD_MODE, uintptr(unsafe.Pointer(&test)))
if r != 0 {
return err
}
if test == mode {
return nil
} else {
return fmt.Errorf("Could not set SPI mode %X", mode)
}
}