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76 lines
1.8 KiB
Go
76 lines
1.8 KiB
Go
// Copyright 2016 The Periph Authors. All rights reserved.
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// Use of this source code is governed under the Apache License, Version 2.0
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// that can be found in the LICENSE file.
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// Package piblaster implements interfacing code is piblaster.
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//
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// See https://github.com/sarfata/pi-blaster for more details. This package
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// relies on pi-blaster being installed and enabled.
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//
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// TODO(maruel): "dtoverlay=pwm" or "dtoverlay=pwm-2chan" works without having
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// to install anything, albeit with less pins supported.
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//
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// Warning
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//
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// piblaster doesn't report what pins is controls so it is easy to misuse this
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// library.
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package piblaster
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import (
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"fmt"
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"io"
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"os"
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"periph.io/x/conn/v3/gpio"
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)
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// SetPWM enables and sets the PWM duty on a GPIO output pin via piblaster.
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//
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// duty must be [0, 1].
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func SetPWM(p gpio.PinIO, duty float32) error {
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if duty < 0 || duty > 1 {
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return fmt.Errorf("piblaster: duty %f is invalid for blaster", duty)
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}
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err := openPiblaster()
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if err == nil {
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_, err = io.WriteString(piblasterHandle, fmt.Sprintf("%d=%f\n", p.Number(), duty))
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}
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return err
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}
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// ReleasePWM releases a GPIO output and leave it floating.
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//
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// This function must be called on process exit for each activated pin
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// otherwise the pin will stay in the state.
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func ReleasePWM(p gpio.PinIO) error {
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err := openPiblaster()
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if err == nil {
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_, err = io.WriteString(piblasterHandle, fmt.Sprintf("release %d\n", p.Number()))
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}
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return err
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}
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//
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var piblasterHandle io.WriteCloser
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func openPiblaster() error {
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if piblasterHandle == nil {
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f, err := os.OpenFile("/dev/pi-blaster", os.O_WRONLY|os.O_APPEND, 0644)
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if err != nil {
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return err
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}
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piblasterHandle = f
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}
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return nil
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}
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func closePiblaster() error {
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if piblasterHandle != nil {
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w := piblasterHandle
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piblasterHandle = nil
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return w.Close()
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}
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return nil
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}
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