93 lines
2.1 KiB
Go
93 lines
2.1 KiB
Go
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package main
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import (
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"fmt"
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"os"
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"sync"
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"k8s.io/klog"
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)
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// gpio is an abstract GPIO output.
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type gpio interface {
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// set returns the GPIO value. The meaning of the logic level is
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// implementation-dependent.
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set(state bool) error
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}
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// bbGPIO implements gpio using BeagleBone's built-in GPIO pins.
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//
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// The value of a GPIO is logically non-inverted: false is 0V, true is 3.3V.
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//
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// The GPIO can be repeatedly set to the same value without performance penalty
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// - only level changes are actually written to hardware registers.
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type bbGPIO struct {
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path string
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mu sync.Mutex
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state bool
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}
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// newBBGPIO returns a BeagleBone GPIO for a given GPIO number.
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//
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// See the following for GPIO pin numbers ('GPIO NO.' column):
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//
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// https://vadl.github.io/images/bbb/P8Header.png
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// https://vadl.github.io/images/bbb/P9Header.png
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func newBBGPIO(num int, value bool) (*bbGPIO, error) {
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path := fmt.Sprintf("/sys/class/gpio/gpio%d", num)
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if _, err := os.Stat(path); err != nil {
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return nil, fmt.Errorf("could not access: %w", err)
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}
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pathDir := path + "/direction"
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if err := os.WriteFile(pathDir, []byte("out"), 0); err != nil {
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return nil, fmt.Errorf("could not set direction: %w", err)
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}
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pathValue := path + "/value"
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res := &bbGPIO{
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path: pathValue,
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}
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if err := res.set(value); err != nil {
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return nil, fmt.Errorf("when setting initial value: %w", err)
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}
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return res, nil
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}
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func (b *bbGPIO) set(state bool) error {
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b.mu.Lock()
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defer b.mu.Unlock()
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if state && !b.state {
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if err := os.WriteFile(b.path, []byte("1"), 0); err != nil {
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return fmt.Errorf("could not turn on: %w", err)
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}
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} else if !state && b.state {
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if err := os.WriteFile(b.path, []byte("0"), 0); err != nil {
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return fmt.Errorf("could not turn off: %w", err)
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}
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}
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b.state = state
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return nil
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}
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// fakeGPIO implements a GPIO that logs state changes.
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type fakeGPIO struct {
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desc string
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mu sync.Mutex
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state bool
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}
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func (b *fakeGPIO) set(state bool) error {
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b.mu.Lock()
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defer b.mu.Unlock()
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if state && !b.state {
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klog.Infof("%s on", b.desc)
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} else if !state && b.state {
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klog.Infof("%s off", b.desc)
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}
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b.state = state
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return nil
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}
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