1
0
mirror of https://github.com/kidoman/embd synced 2024-12-23 05:10:05 +01:00
embd/driver/linux/i2c/bus.go

279 lines
5.1 KiB
Go
Raw Normal View History

package i2c
import (
"fmt"
"os"
"reflect"
"sync"
"syscall"
"time"
"unsafe"
)
const (
delay = 20
slaveCmd = 0x0703 // Cmd to set slave address
rdrwCmd = 0x0707 // Cmd to read/write data together
rd = 0x0001
)
type i2c_msg struct {
addr uint16
flags uint16
len uint16
buf uintptr
}
type i2c_rdwr_ioctl_data struct {
msgs uintptr
nmsg uint32
}
type bus struct {
l byte
file *os.File
addr byte
mu sync.Mutex
}
func newBus(l byte) (*bus, error) {
b := &bus{l: l}
var err error
if b.file, err = os.OpenFile(fmt.Sprintf("/dev/i2c-%v", b.l), os.O_RDWR, os.ModeExclusive); err != nil {
return nil, err
}
return b, nil
}
func (b *bus) Close() error {
b.mu.Lock()
defer b.mu.Unlock()
return b.file.Close()
}
func (b *bus) setAddress(addr byte) (err error) {
if addr != b.addr {
if _, _, errno := syscall.Syscall(syscall.SYS_IOCTL, b.file.Fd(), slaveCmd, uintptr(addr)); errno != 0 {
err = syscall.Errno(errno)
return
}
b.addr = addr
}
return
}
func (b *bus) ReadByte(addr byte) (value byte, err error) {
b.mu.Lock()
defer b.mu.Unlock()
if err = b.setAddress(addr); err != nil {
return
}
bytes := make([]byte, 1)
n, err := b.file.Read(bytes)
if n != 1 {
err = fmt.Errorf("i2c: Unexpected number (%v) of bytes read", n)
}
value = bytes[0]
return
}
func (b *bus) WriteByte(addr, value byte) (err error) {
b.mu.Lock()
defer b.mu.Unlock()
if err = b.setAddress(addr); err != nil {
return
}
n, err := b.file.Write([]byte{value})
if n != 1 {
err = fmt.Errorf("i2c: Unexpected number (%v) of bytes written in WriteByte", n)
}
return
}
func (b *bus) WriteBytes(addr byte, value []byte) (err error) {
b.mu.Lock()
defer b.mu.Unlock()
if err = b.setAddress(addr); err != nil {
return err
}
for i := range value {
n, err := b.file.Write([]byte{value[i]})
if n != 1 {
return fmt.Errorf("i2c: Unexpected number (%v) of bytes written in WriteBytes", n)
}
if err != nil {
return err
}
time.Sleep(delay * time.Millisecond)
}
return nil
}
func (b *bus) ReadFromReg(addr, reg byte, value []byte) (err error) {
b.mu.Lock()
defer b.mu.Unlock()
if err = b.setAddress(addr); err != nil {
return
}
hdrp := (*reflect.SliceHeader)(unsafe.Pointer(&value))
var messages [2]i2c_msg
messages[0].addr = uint16(addr)
messages[0].flags = 0
messages[0].len = 1
messages[0].buf = uintptr(unsafe.Pointer(&reg))
messages[1].addr = uint16(addr)
messages[1].flags = rd
messages[1].len = uint16(len(value))
messages[1].buf = uintptr(unsafe.Pointer(hdrp.Data))
var packets i2c_rdwr_ioctl_data
packets.msgs = uintptr(unsafe.Pointer(&messages))
packets.nmsg = 2
if _, _, errno := syscall.Syscall(syscall.SYS_IOCTL, b.file.Fd(), rdrwCmd, uintptr(unsafe.Pointer(&packets))); errno != 0 {
return syscall.Errno(errno)
}
return nil
}
func (b *bus) ReadByteFromReg(addr, reg byte) (value byte, err error) {
buf := make([]byte, 1)
if err = b.ReadFromReg(addr, reg, buf); err != nil {
return
}
value = buf[0]
return
}
func (b *bus) ReadWordFromReg(addr, reg byte) (value uint16, err error) {
buf := make([]byte, 2)
if err = b.ReadFromReg(addr, reg, buf); err != nil {
return
}
value = uint16((uint16(buf[0]) << 8) | uint16(buf[1]))
return
}
func (b *bus) WriteToReg(addr, reg byte, value []byte) (err error) {
b.mu.Lock()
defer b.mu.Unlock()
if err = b.setAddress(addr); err != nil {
return
}
outbuf := append([]byte{reg}, value...)
hdrp := (*reflect.SliceHeader)(unsafe.Pointer(&outbuf))
var message i2c_msg
message.addr = uint16(addr)
message.flags = 0
message.len = uint16(len(outbuf))
message.buf = uintptr(unsafe.Pointer(&hdrp.Data))
var packets i2c_rdwr_ioctl_data
packets.msgs = uintptr(unsafe.Pointer(&message))
packets.nmsg = 1
if _, _, errno := syscall.Syscall(syscall.SYS_IOCTL, b.file.Fd(), rdrwCmd, uintptr(unsafe.Pointer(&packets))); errno != 0 {
err = syscall.Errno(errno)
return
}
return
}
func (b *bus) WriteByteToReg(addr, reg, value byte) (err error) {
b.mu.Lock()
defer b.mu.Unlock()
if err = b.setAddress(addr); err != nil {
return
}
outbuf := [...]byte{
reg,
value,
}
var message i2c_msg
message.addr = uint16(addr)
message.flags = 0
message.len = uint16(len(outbuf))
message.buf = uintptr(unsafe.Pointer(&outbuf))
var packets i2c_rdwr_ioctl_data
packets.msgs = uintptr(unsafe.Pointer(&message))
packets.nmsg = 1
if _, _, errno := syscall.Syscall(syscall.SYS_IOCTL, b.file.Fd(), rdrwCmd, uintptr(unsafe.Pointer(&packets))); errno != 0 {
err = syscall.Errno(errno)
return
}
return
}
func (b *bus) WriteWordToReg(addr, reg byte, value uint16) (err error) {
b.mu.Lock()
defer b.mu.Unlock()
if err = b.setAddress(addr); err != nil {
return
}
outbuf := [...]byte{
reg,
byte(value >> 8),
byte(value),
}
var messages i2c_msg
messages.addr = uint16(addr)
messages.flags = 0
messages.len = uint16(len(outbuf))
messages.buf = uintptr(unsafe.Pointer(&outbuf))
var packets i2c_rdwr_ioctl_data
packets.msgs = uintptr(unsafe.Pointer(&messages))
packets.nmsg = 1
if _, _, errno := syscall.Syscall(syscall.SYS_IOCTL, b.file.Fd(), rdrwCmd, uintptr(unsafe.Pointer(&packets))); errno != 0 {
err = syscall.Errno(errno)
return
}
return
}