mirror of https://github.com/periph/devices
gsexton
1 year ago
committed by
GitHub
parent
eb90d53534
commit
7555373ca1
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// Copyright 2025 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 pcf857x_test
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import (
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"fmt"
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"log"
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"periph.io/x/conn/v3/gpio"
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"periph.io/x/conn/v3/i2c/i2creg"
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"periph.io/x/devices/v3/pcf857x"
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"periph.io/x/host/v3"
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)
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func Example() {
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// Make sure periph is initialized.
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if _, err := host.Init(); err != nil {
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log.Fatal(err)
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}
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// Open default I²C bus.
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bus, err := i2creg.Open("")
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if err != nil {
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log.Fatalf("failed to open I²C: %v", err)
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}
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defer bus.Close()
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// Create a new I2C IO extender
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extender, err := pcf857x.New(bus, pcf857x.DefaultAddress, pcf857x.PCF8574)
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if err != nil {
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log.Fatalln(err)
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}
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for _, pin := range extender.Pins {
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err = pin.In(gpio.Float, gpio.NoEdge)
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if err != nil {
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log.Fatalln(err)
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}
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level := pin.Read()
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fmt.Printf("%s\t%s\n", pin.Name(), level.String())
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}
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if err != nil {
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log.Fatalln(err)
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}
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}
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// Copyright 2025 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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// This package provides a driver for the TI/NXP PCF857X I2C I/O Expander. These
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// devices provide 8 pins (PCF8574) or 16 pins (PCF8575) of
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// "quasi-bidirectional" input/output. This device is commonly used in LCD
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// backpacks, particularly those sold as LCD2004, LCD1602.
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//
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// The PCF8575 is a 16-pin device that is functionally identical to the PCF8574.
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// When communicating with the PCF8575 reads and writes are 2 bytes wide, while
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// they're one byte wide with the PCF85754
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//
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// # Datasheet
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//
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// https://www.ti.com/lit/ds/symlink/pcf8574.pdf
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//
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// A good description of the I2C LCD backpack usage can be found here:
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//
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// https://www.handsontec.com/dataspecs/I2C_2004_LCD.pdf
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//
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// Adafruit also sells a breakout board with these chips. See here:
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//
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// https://www.adafruit.com/product/5611
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//
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// # Notes
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//
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// This device is very simple and doesn't have functionality that similar
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// devices do. Specifically, GPIO Read() consists of writing a High out a pin,
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// and then reading it to see if it is still high, or if it has transitioned to
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// low.
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//
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// Setting a pin to Low activates an Open Drain to ground.
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//
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// You cannot detect edge change on a specific pin. There is an interrupt pin
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// that can be used to detect a change on the GPIO pins, but it doesn't tell you
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// which pin changed.
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//
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// This chip doesn't implement normal i2c register architectures. You write 8 or
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// 16 bits out, and that sets the corresponding pins, or you read 8/16 bits and
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// get the state of the pins.
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package pcf857x
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import (
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"errors"
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"fmt"
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"sync"
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"time"
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"periph.io/x/conn/v3/gpio"
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"periph.io/x/conn/v3/gpio/gpioreg"
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"periph.io/x/conn/v3/i2c"
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"periph.io/x/conn/v3/pin"
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)
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// Variant represents the actual chip model.
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type Variant string
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const (
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PCF8574 Variant = "PCF8574"
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PCF8575 Variant = "PCF8575"
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DefaultAddress uint16 = 0x20
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)
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var (
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ErrNotImplmented error = errors.New("pcf857x: not implemented")
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)
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// Dev is representation of a PCF857x device.
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type Dev struct {
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// The pins exposed by the device. For PCF8574, this will be 8 pins, and
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// 16 pins for the PCF8575
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Pins []gpio.PinIO
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mask gpio.GPIOValue
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width int
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chipType Variant
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mu sync.Mutex
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d *i2c.Dev
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value gpio.GPIOValue
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groups []Group
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}
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type Group struct {
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pins []pcfPin
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dev *Dev
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}
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// New creates a new PCF857x io expander and returns it. chip should be one of
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// the Variant constants above.
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func New(bus i2c.Bus, address uint16, chip Variant) (*Dev, error) {
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dev := &Dev{d: &i2c.Dev{Bus: bus, Addr: address},
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chipType: chip}
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if chip == PCF8574 {
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dev.width = 8
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} else {
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dev.width = 16
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}
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dev.mask = gpio.GPIOValue((1 << dev.width) - 1)
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dev.Pins = make([]gpio.PinIO, dev.width)
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sDev := dev.String()
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for ix := range dev.width {
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name := fmt.Sprintf("%s_GPIO%d", sDev, ix)
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dev.Pins[ix] = &pcfPin{dev: dev, number: ix, name: name}
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_ = gpioreg.Register(dev.Pins[ix])
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}
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return dev, nil
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}
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// Group returns a GPIO Group comprised of the specified pin numbers. A
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// gpio.Group allows you to perform writes to multiple pins in one operation.
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func (dev *Dev) Group(pinNumbers ...int) (gpio.Group, error) {
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dev.mu.Lock()
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defer dev.mu.Unlock()
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gr := Group{dev: dev, pins: make([]pcfPin, len(pinNumbers))}
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for ix, pinNumber := range pinNumbers {
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if p, ok := dev.Pins[pinNumber].(*pcfPin); ok {
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gr.pins[ix] = *p
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}
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}
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dev.groups = append(dev.groups, gr)
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return &gr, nil
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}
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// Halt shuts down the device, and frees any pin groups.
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func (dev *Dev) Halt() error {
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dev.mu.Lock()
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defer dev.mu.Unlock()
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for _, gr := range dev.groups {
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_ = gr.Halt()
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}
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dev.groups = make([]Group, 0)
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dev.Pins = make([]gpio.PinIO, 0)
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return nil
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}
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// read performs the low level i2c read operation from the device.
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func (dev *Dev) read(mask gpio.GPIOValue) (gpio.GPIOValue, error) {
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// Before you can read a pin, you must have set it to high. If nothing
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// pulls that down, then it's high. If it's pulled down, it's low.
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err := dev.write(mask, mask)
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if err != nil {
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return 0, fmt.Errorf("pcf857x: %w", err)
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}
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dev.mu.Lock()
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defer dev.mu.Unlock()
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byteCount := 1
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if dev.width > 8 {
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byteCount += 1
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}
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r := make([]byte, byteCount)
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err = dev.d.Tx(nil, r)
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if err != nil {
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return 0, fmt.Errorf("pcf857x: %w", err)
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}
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result := gpio.GPIOValue(r[0])
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if byteCount > 1 {
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result |= gpio.GPIOValue(r[1]) << 8
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}
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// turn off the bits we just read so that the next time through, we force
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// the write high on them.
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dev.value = result
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result &= mask
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return result, nil
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}
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// write performs the low-level write to the device. If the resulting value of
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// the device is unchanged, the write is skipped.
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func (dev *Dev) write(value, mask gpio.GPIOValue) error {
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dev.mu.Lock()
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defer dev.mu.Unlock()
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wrValue := dev.value & (dev.mask ^ mask)
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wrValue |= (value & mask)
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if dev.value == wrValue {
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return nil
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}
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byteCount := 1
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if dev.width > 8 {
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byteCount += 1
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}
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w := make([]byte, byteCount)
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for ix := range byteCount {
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w[ix] = byte(wrValue >> (ix * 8))
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}
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err := dev.d.Tx(w, nil)
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if err == nil {
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dev.value = wrValue
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} else {
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err = fmt.Errorf("pcf857x: %w", err)
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}
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return err
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}
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func (dev *Dev) String() string {
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return fmt.Sprintf("%s_%x", dev.chipType, dev.d.Addr)
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}
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// Pins returns the set of pins that make up this group.
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func (gr *Group) Pins() []pin.Pin {
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pins := make([]pin.Pin, len(gr.pins))
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for ix := range len(gr.pins) {
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pins[ix] = &gr.pins[ix]
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}
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return pins
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}
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// This converts a mask for a group operation into a mask suitable for writing
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// to the device.
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func (gr *Group) groupMaskToDevMask(mask gpio.GPIOValue) gpio.GPIOValue {
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m := gpio.GPIOValue(0)
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for ix := range len(gr.pins) {
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currentBit := gpio.GPIOValue(1 << ix)
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if (mask & currentBit) == currentBit {
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pinBit := gpio.GPIOValue(1) << gr.pins[ix].number
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m |= pinBit
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}
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}
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return m
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}
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// Return the GPIO pin by offset within the group.
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func (gr *Group) ByOffset(offset int) pin.Pin {
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return &gr.pins[offset]
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}
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// Return the GPIO pin by name.
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func (gr *Group) ByName(name string) pin.Pin {
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for ix := range len(gr.pins) {
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if gr.pins[ix].name == name {
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return &gr.pins[ix]
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}
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}
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return nil
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}
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// Return the GPIO pin by it's pin number on the device.
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func (gr *Group) ByNumber(number int) pin.Pin {
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for ix := range len(gr.pins) {
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if gr.pins[ix].number == number {
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return &gr.pins[ix]
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}
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}
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return nil
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}
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// Out writes the specified value to the device. Only pins identified by mask
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// are modified.
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func (gr *Group) Out(value, mask gpio.GPIOValue) error {
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if mask == 0 {
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mask = (1 << len(gr.pins)) - 1
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}
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wrMask := gr.groupMaskToDevMask(mask)
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wr := gpio.GPIOValue(0)
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for ix, pin := range gr.pins {
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if (value & gpio.GPIOValue(1<<ix)) > 0 {
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wr |= 1 << pin.number
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}
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}
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return gr.dev.write(wr, wrMask)
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}
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// Read returns the current values of the pins within the group identified by
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// mask.
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func (gr *Group) Read(mask gpio.GPIOValue) (gpio.GPIOValue, error) {
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if mask == 0 {
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mask = (1 << len(gr.pins)) - 1
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}
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devMask := gr.groupMaskToDevMask(mask)
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v, err := gr.dev.read(devMask)
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if err != nil {
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return 0, fmt.Errorf("pcf857x: %w", err)
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}
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// Now, convert it back to a group value.
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result := gpio.GPIOValue(0)
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for ix, pin := range gr.pins {
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currentBit := gpio.GPIOValue(1 << ix)
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if (mask & currentBit) == currentBit {
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if (v & gpio.GPIOValue(1<<pin.number)) > 0 {
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result |= currentBit
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}
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}
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}
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return result, nil
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}
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// This chip does not support waiting for edge on either a pin or a group. There
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// is an interrupt pin, but you can't set a mask of pins that will trigger it. To
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// do that, you connect a GPIO pin from the host device that supports WaitForEdge
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// to monitor the INTR pin.
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func (gr *Group) WaitForEdge(timeout time.Duration) (number int, edge gpio.Edge, err error) {
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// TODO: Implement wait for edge in the same way that it is for mcp23008
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return 0, gpio.NoEdge, ErrNotImplmented
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}
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// Halt stops the pin group. It cannot be used after this call.
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func (gr *Group) Halt() error {
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gr.pins = make([]pcfPin, 0)
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gr.dev = nil
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return nil
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}
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func (gr *Group) String() string {
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s := gr.dev.String() + "[ "
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for ix := range len(gr.pins) {
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s += fmt.Sprintf("%d ", gr.pins[ix].Number())
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}
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s += "]"
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return s
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}
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var _ gpio.Group = &Group{}
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@ -0,0 +1,216 @@
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// Copyright 2025 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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//
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// This test assumes you have a PCF8575 and that the data pins are jumpered
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//
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// 0 => 8
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// 1 => 9
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// ...
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// 7 => 15
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package pcf857x
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import (
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"errors"
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"strings"
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"testing"
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"periph.io/x/conn/v3/gpio"
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"periph.io/x/conn/v3/gpio/gpioreg"
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"periph.io/x/conn/v3/i2c/i2ctest"
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)
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func getDev(recordingName string, t *testing.T) (*Dev, error) {
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// Create a new I2C IO extender
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bus := i2ctest.Playback{Ops: recordingData[recordingName]}
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extender, err := New(&bus, DefaultAddress, PCF8575)
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if err != nil {
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t.Error(err)
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}
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return extender, err
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}
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// Test basic dev and pin functions.
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func TestBasic(t *testing.T) {
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dev, err := getDev(t.Name(), t)
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if err != nil {
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return
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}
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t.Logf("dev=%#v", dev)
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pin := dev.Pins[1]
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t.Logf("pin=%#v", pin)
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s := dev.String()
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if len(s) == 0 {
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t.Error("String() failure")
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} //
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if len(dev.Pins) != 16 {
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t.Errorf("expected 16 GPIO pins. Found %d", len(dev.Pins))
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}
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e := pin.PWM(10, 10)
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if !errors.Is(e, ErrNotImplmented) {
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t.Errorf("PWM() expected ErrNotImplemented. Received %#v", e)
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}
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if pin.Halt() != nil {
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t.Error("expected nil on pin.Halt()")
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}
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if pin.Name() != pin.String() {
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t.Error("pin.Name()!=pin.String()")
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}
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if !strings.HasPrefix(pin.Name(), dev.String()) {
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t.Errorf("Expected pin.Name()=%s to start with dev.String()=%s", pin.Name(), dev.String())
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}
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err = dev.Halt()
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if err != nil {
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t.Error(err)
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}
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}
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// Test that the pins are registered in gpioreg as expected.
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func TestGPIOReg(t *testing.T) {
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dev, err := getDev(t.Name(), t)
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if err != nil {
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return
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}
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for ix := range dev.width {
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p := dev.Pins[ix]
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if p.Number() != ix {
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t.Errorf("pin.Number() does not match ordinal position %d! Found %d", ix, p.Number())
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}
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pReg := gpioreg.ByName(p.Name())
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if pReg == nil {
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t.Errorf("pin %s not found in gpioreg", p.Name())
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}
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}
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}
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// This test goes through the pins from 0-7, and writes to them and then reads
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// the value on pin+8 and verifies it's correct. Then, it reverses direction and
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// writes to pin[8] and reads from pin[0].
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func TestPinsSequentially(t *testing.T) {
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dev, err := getDev(t.Name(), t)
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if err != nil {
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return
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}
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limit := dev.width >> 1
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for ixOuter := range limit {
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// Iterate over the lower 8 pins
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for ixInner := range limit {
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// Sequentially, set each pin to High if it's not the value of ix
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p := dev.Pins[ixInner]
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pRead := dev.Pins[ixInner+limit]
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for direction := range 2 {
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writeLevel := gpio.Level(ixInner != ixOuter)
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err = p.Out(writeLevel)
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if err != nil {
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t.Error(err)
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}
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readVal := pRead.Read()
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if readVal != writeLevel {
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t.Errorf("wrote %t to pin[%d]. Expected same on pin[%d], found %t",
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writeLevel,
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p.Number(),
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pRead.Number(),
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||||
readVal)
|
||||
}
|
||||
if direction == 0 {
|
||||
// swap the direction so we're now going pin[8] => pin[0] and stay in
|
||||
// the loop to repeat the test.
|
||||
x := pRead
|
||||
pRead = p
|
||||
p = x
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
// This tests the group functionality.
|
||||
func TestGroup(t *testing.T) {
|
||||
dev, err := getDev(t.Name(), t)
|
||||
|
||||
if err != nil {
|
||||
return
|
||||
}
|
||||
defer func() { _ = dev.Halt() }()
|
||||
|
||||
set1 := make([]int, dev.width>>1)
|
||||
set2 := make([]int, dev.width>>1)
|
||||
for ix := range len(set1) {
|
||||
set1[ix] = ix
|
||||
set2[ix] = ix + len(set1)
|
||||
}
|
||||
gr1, err := dev.Group(set1...)
|
||||
if err != nil {
|
||||
return
|
||||
}
|
||||
gr2, err := dev.Group(set2...)
|
||||
if err != nil {
|
||||
return
|
||||
}
|
||||
// Test the basic group functionality. Note that for group1, pinOffset==pin.Number, but
|
||||
// for group2, pinOffset!=pin.Number
|
||||
grTest := gr1
|
||||
for range 2 {
|
||||
for pinNumber, pin := range grTest.Pins() {
|
||||
x := grTest.ByNumber(pin.Number())
|
||||
if x == nil {
|
||||
t.Errorf("group.ByNumber() returned nil for pin %d", pin.Number())
|
||||
}
|
||||
x = grTest.ByOffset(pinNumber)
|
||||
if x == nil {
|
||||
t.Errorf("group.ByOffset returned nil for pin number %d", pinNumber)
|
||||
} else {
|
||||
if x.Number() != pin.Number() {
|
||||
t.Errorf("group.ByOffset() didn't return the expected pin. Expected %d, found %d", pin.Number(), x.Number())
|
||||
}
|
||||
}
|
||||
x = grTest.ByName(pin.Name())
|
||||
if x == nil || x.Name() != pin.Name() {
|
||||
t.Error("group.ByName() didn't find a pin or returned the wrong pin!")
|
||||
}
|
||||
}
|
||||
grTest = gr2
|
||||
}
|
||||
if len(gr1.String()) == 0 {
|
||||
t.Error("group.String() didn't return a value")
|
||||
}
|
||||
// Test the read/write functionality.
|
||||
limit := (1 << len(set1))
|
||||
var read gpio.GPIOValue
|
||||
for groupNumber := range 2 {
|
||||
for val := range limit {
|
||||
err = gr1.Out(gpio.GPIOValue(val), 0)
|
||||
if err != nil {
|
||||
t.Error(err)
|
||||
}
|
||||
read, err = gr2.Read(0)
|
||||
if err != nil {
|
||||
t.Error(err)
|
||||
}
|
||||
if read != gpio.GPIOValue(val) {
|
||||
t.Errorf("Error writing/reading groups. Wrote %d on write group %s, read %d on read group%s", val, gr1, read, gr2)
|
||||
}
|
||||
}
|
||||
if groupNumber == 0 {
|
||||
x := gr1
|
||||
gr1 = gr2
|
||||
gr2 = x
|
||||
}
|
||||
}
|
||||
err = gr1.Halt()
|
||||
if err != nil {
|
||||
t.Error(err)
|
||||
}
|
||||
err = gr2.Halt()
|
||||
if err != nil {
|
||||
t.Error(err)
|
||||
}
|
||||
}
|
||||
File diff suppressed because it is too large
Load Diff
@ -0,0 +1,92 @@
|
||||
// Copyright 2025 The Periph Authors. All rights reserved.
|
||||
// Use of this source code is governed under the Apache License, Version 2.0
|
||||
// that can be found in the LICENSE file.
|
||||
|
||||
package pcf857x
|
||||
|
||||
import (
|
||||
"log"
|
||||
"time"
|
||||
|
||||
"periph.io/x/conn/v3/gpio"
|
||||
"periph.io/x/conn/v3/physic"
|
||||
)
|
||||
|
||||
type pcfPin struct {
|
||||
dev *Dev
|
||||
number int
|
||||
name string
|
||||
}
|
||||
|
||||
func (pin *pcfPin) DefaultPull() gpio.Pull {
|
||||
return gpio.Float
|
||||
}
|
||||
|
||||
func (pin *pcfPin) Function() string {
|
||||
return "Out"
|
||||
}
|
||||
|
||||
func (pcf *pcfPin) Halt() error {
|
||||
return nil
|
||||
}
|
||||
|
||||
func (pin *pcfPin) In(pull gpio.Pull, edge gpio.Edge) error {
|
||||
// To use a pin for input, you must write a High to that pin, and then
|
||||
// perform the read. The chip doesn't natively support pullup/pulldown.
|
||||
//
|
||||
// Refer to the datasheet for more information.
|
||||
v := gpio.GPIOValue(1 << pin.number)
|
||||
return pin.dev.write(v, v)
|
||||
}
|
||||
|
||||
func (pin *pcfPin) Name() string {
|
||||
return pin.name
|
||||
}
|
||||
|
||||
func (pin *pcfPin) Number() int {
|
||||
return pin.number
|
||||
}
|
||||
|
||||
func (pin *pcfPin) Out(l gpio.Level) error {
|
||||
value := gpio.GPIOValue(0)
|
||||
mask := gpio.GPIOValue(1 << pin.number)
|
||||
if l {
|
||||
value = mask
|
||||
}
|
||||
return pin.dev.write(value, mask)
|
||||
}
|
||||
|
||||
func (pin *pcfPin) Pull() gpio.Pull {
|
||||
return gpio.Float
|
||||
}
|
||||
|
||||
func (pin *pcfPin) Read() gpio.Level {
|
||||
|
||||
result := gpio.Low
|
||||
mask := gpio.GPIOValue(1 << pin.number)
|
||||
|
||||
value, err := pin.dev.read(mask)
|
||||
if err == nil {
|
||||
result = (value & mask) == mask
|
||||
} else {
|
||||
log.Println(err)
|
||||
}
|
||||
|
||||
return result
|
||||
}
|
||||
|
||||
func (pin *pcfPin) PWM(duty gpio.Duty, f physic.Frequency) error {
|
||||
return ErrNotImplmented
|
||||
}
|
||||
|
||||
func (pin *pcfPin) String() string {
|
||||
return pin.name
|
||||
}
|
||||
|
||||
// This device has an interrupt pin that can detect a change on the GPIO lines,
|
||||
// however it doesn't let you detect a change on a specific pin.
|
||||
func (pin *pcfPin) WaitForEdge(timeout time.Duration) bool {
|
||||
return false
|
||||
}
|
||||
|
||||
var _ gpio.PinIO = &pcfPin{}
|
||||
Loading…
Reference in New Issue