mirror of
https://github.com/stianeikeland/go-rpio.git
synced 2025-03-15 17:38:44 +01:00
Basic functionality working
Added support for: - pin mode - write - read
This commit is contained in:
Stian Eikeland
parent
942b04b4d0
commit
cc2855b1d8
248
rpio.go
Normal file
248
rpio.go
Normal file
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@ -0,0 +1,248 @@
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/*
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Package rpio provides GPIO access on the Raspberry PI without any need
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for external c libraries (ex: WiringPI or BCM2835).
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Supports simple operations such as:
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- Pin mode/direction (input/output)
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- Pin write (high/low)
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- Pin read (high/low)
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Example of use:
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rpio.Open()
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defer rpio.Close()
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pin := rpio.Pin(4)
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pin.Output()
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for {
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pin.Toggle()
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time.Sleep(time.Second)
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}
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The library use the raw BCM2835 pinouts, not the ports as they are mapped
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on the output pins for the raspberry pi
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Rev 1 Raspberry Pi
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+------+------+--------+
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| GPIO | Phys | Name |
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+------+------+--------+
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| 0 | 3 | SDA |
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| 1 | 5 | SCL |
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| 4 | 7 | GPIO 7 |
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| 7 | 26 | CE1 |
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| 8 | 24 | CE0 |
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| 9 | 21 | MISO |
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| 10 | 19 | MOSI |
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| 11 | 23 | SCLK |
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| 14 | 8 | TxD |
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| 15 | 10 | RxD |
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| 17 | 11 | GPIO 0 |
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| 18 | 12 | GPIO 1 |
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| 21 | 13 | GPIO 2 |
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| 22 | 15 | GPIO 3 |
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| 23 | 16 | GPIO 4 |
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| 24 | 18 | GPIO 5 |
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| 25 | 22 | GPIO 6 |
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+------+------+--------+
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See the spec for full details of the BCM2835 controller:
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http://www.raspberrypi.org/wp-content/uploads/2012/02/BCM2835-ARM-Peripherals.pdf
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*/
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package main
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import (
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"os"
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"reflect"
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"sync"
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"syscall"
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"unsafe"
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)
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type Direction uint8
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type Pin uint8
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type State uint8
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// Memory offsets for gpio, see the spec for more details
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const (
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bcm2835Base = 0x20000000
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gpioBase = bcm2835Base + 0x200000
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memLength = 4096
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pinMask uint32 = 7 // 0b111 - pinmode is 3 bits
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)
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// Pin direction, a pin can be set in Input or Output mode
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const (
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Input Direction = iota
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Output
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)
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// State of pin, High / Low
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const (
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Low State = iota
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High
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)
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// Arrays for 8 / 32 bit access to memory and a semaphore for write locking
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var (
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memlock sync.Mutex
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mem []uint32
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mem8 []uint8
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)
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// Set pin as Input
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func (pin Pin) Input() {
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PinMode(pin, Input)
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}
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// Set pin as Output
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func (pin Pin) Output() {
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PinMode(pin, Output)
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}
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// Set pin High
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func (pin Pin) High() {
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WritePin(pin, High)
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}
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// Set pin Low
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func (pin Pin) Low() {
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WritePin(pin, Low)
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}
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// Toggle pin state
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func (pin Pin) Toggle() {
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TogglePin(pin)
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}
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// Set pin Direction
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func (pin Pin) Mode(dir Direction) {
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PinMode(pin, dir)
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}
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// Set pin state (high/low)
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func (pin Pin) Write(state State) {
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WritePin(pin, state)
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}
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// Read pin state (high/low)
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func (pin Pin) Read() State {
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return ReadPin(pin)
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}
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// WritePin sets the direction of a given pin (Input or Output)
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func PinMode(pin Pin, direction Direction) {
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// Pin fsel register, 0 or 1 depending on bank
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fsel := uint8(pin) / 10
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shift := (uint8(pin) % 10) * 3
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memlock.Lock()
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if direction == Input {
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mem[fsel] = mem[fsel] &^ (pinMask << shift)
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} else {
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mem[fsel] = (mem[fsel] &^ (pinMask << shift)) | (1 << shift)
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}
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memlock.Unlock()
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}
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// WritePin sets a given pin High or Low
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// by setting the clear or set registers respectively
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func WritePin(pin Pin, state State) {
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p := uint8(pin)
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// Clear register, 10 / 11 depending on bank
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// Set register, 7 / 8 depending on bank
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clearReg := p/32 + 10
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setReg := p/32 + 7
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memlock.Lock()
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if state == Low {
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mem[clearReg] = 1 << (p & 31)
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} else {
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mem[setReg] = 1 << (p & 31)
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}
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memlock.Unlock()
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}
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// Read the state of a
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func ReadPin(pin Pin) State {
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// Input level register offset (13 / 14 depending on bank)
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levelReg := uint8(pin)/32 + 13
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if (mem[levelReg] & (1 << uint8(pin))) != 0 {
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return High
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}
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return Low
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}
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// Toggle a pin state (high -> low -> high)
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// TODO: probably possible to do this much faster without read
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func TogglePin(pin Pin) {
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switch ReadPin(pin) {
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case Low:
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pin.High()
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case High:
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pin.Low()
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}
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}
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// Open and memory map GPIO memory range from /dev/mem .
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// Some reflection magic is used to convert it to a unsafe []uint32 pointer
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func Open() (err error) {
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var file *os.File
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// Open fd for rw mem access
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file, err = os.OpenFile(
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"/dev/mem",
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os.O_RDWR|os.O_SYNC,
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0)
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if err != nil {
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return
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}
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// FD can be closed after memory mapping
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defer file.Close()
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memlock.Lock()
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// Memory map GPIO registers to byte array
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mem8, err = syscall.Mmap(
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int(file.Fd()),
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gpioBase,
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memLength,
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syscall.PROT_READ|syscall.PROT_WRITE,
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syscall.MAP_SHARED)
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if err != nil {
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return
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}
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// Convert mapped byte memory to unsafe []uint32 pointer, adjust length as needed
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header := *(*reflect.SliceHeader)(unsafe.Pointer(&mem8))
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header.Len /= (32 / 8) // (32 bit = 4 bytes)
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header.Cap /= (32 / 8)
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mem = *(*[]uint32)(unsafe.Pointer(&header))
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memlock.Unlock()
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return nil
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}
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// Close unmaps GPIO memory
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func Close() {
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memlock.Lock()
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syscall.Munmap(mem8)
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memlock.Unlock()
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}
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151
rpio/rpio.go
151
rpio/rpio.go
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@ -1,151 +0,0 @@
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package rpio
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import (
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"fmt"
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"os"
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"reflect"
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"sync"
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"syscall"
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"unsafe"
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)
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type Direction uint8
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type Pin uint8
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type State uint8
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// Memory offsets for gpio, see the spec for more details
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// http://www.raspberrypi.org/wp-content/uploads/2012/02/BCM2835-ARM-Peripherals.pdf
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const (
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bcm2835Base = 0x20000000
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gpioBase = bcm2835Base + 0x200000
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pinmask uint32 = 7 // 0b111
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)
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// Pin modes (input, output)
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const (
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INPUT Direction = iota
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OUTPUT
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)
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// State of pin, high/low
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const (
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LOW State = iota
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HIGH
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)
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var (
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mem []uint32
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mem8 []uint8
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memlock sync.Mutex
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)
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func (pin Pin) High() {
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WritePin(uint8(pin), HIGH)
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}
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func (pin Pin) Low() {
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WritePin(uint8(pin), LOW)
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}
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func (pin Pin) Mode(dir Direction) {
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PinMode(uint8(pin), dir)
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}
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func (pin Pin) Write(state State) {
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WritePin(uint8(pin), state)
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}
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func (pin Pin) Read() State {
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return ReadPin(uint8(pin))
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}
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func PinMode(pin uint8, direction Direction) {
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fsel := pin / 10
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shift := (pin % 10) * 3
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fmt.Println(pin, fsel, shift)
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fmt.Printf("0b%b \n", mem[fsel])
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memlock.Lock()
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if direction == INPUT {
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fmt.Printf("0b%b\n\n", mem[fsel]&^(pinmask<<shift))
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} else {
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fmt.Printf("0b%b\n\n", mem[fsel]&^(pinmask<<shift)|(1<<shift))
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}
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memlock.Unlock()
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}
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func WritePin(pin uint8, state State) {
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clearReg := pin/32 + 10
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setReg := pin/32 + 7
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memlock.Lock()
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if state == LOW {
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fmt.Printf("0b%b \n", mem[clearReg])
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fmt.Printf("0b%b\n\n", 1<<(pin&31))
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} else {
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fmt.Printf("0b%b \n", mem[setReg])
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fmt.Printf("0b%b\n\n", 1<<(pin&31))
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}
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memlock.Unlock()
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}
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func ReadPin(pin uint8) State {
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// input level register offset
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levelReg := pin/32 + 13
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//memlock.Lock()
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fmt.Printf("0b%b \n", mem[levelReg])
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fmt.Printf("0b%b \n", mem[levelReg]&(1<<pin))
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if (mem[levelReg] & (1 << pin)) != 0 {
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return HIGH
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}
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return LOW
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}
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func Open() (err error) {
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var file *os.File
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// Open fd for rw mem access
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file, err = os.OpenFile("/dev/mem", os.O_RDWR|os.O_SYNC, 0)
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if err != nil {
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return
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}
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// Can be closed after memory mapping
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defer file.Close()
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memlock.Lock()
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// Memory map GPIO registers to byte array
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mem8, err = syscall.Mmap(int(file.Fd()), gpioBase, 4*1024, syscall.PROT_READ, syscall.MAP_SHARED)
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if err != nil {
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return
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}
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// Convert mapped byte memory to unsafe []uint32 pointer, adjust length as needed
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header := *(*reflect.SliceHeader)(unsafe.Pointer(&mem8))
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header.Len /= (32 / 8) // (32 bit = 4 bytes)
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header.Cap /= (32 / 8)
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mem = *(*[]uint32)(unsafe.Pointer(&header))
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memlock.Unlock()
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return nil
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}
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func Close() {
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// Unmap memory
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memlock.Lock()
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syscall.Munmap(mem8)
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memlock.Unlock()
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}
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