mirror of
https://github.com/stianeikeland/go-rpio.git
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Merge pull request #50 from wfd3/master
Updated to support Raspberry Pi 4 GPIO Base Address
This commit is contained in:
commit
b62d4bed37
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@ -23,10 +23,10 @@ func main() {
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// Pull up and read value
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pin.PullUp()
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fmt.Printf("PullUp: %d\n", pin.Read())
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fmt.Printf("PullUp: %d, %d\n", pin.Read(), pin.ReadPull())
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// Pull down and read value
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pin.PullDown()
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fmt.Printf("PullDown: %d\n", pin.Read())
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fmt.Printf("PullDown: %d, %d\n", pin.Read(), pin.ReadPull())
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}
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133
rpio.go
133
rpio.go
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@ -63,12 +63,15 @@ See the spec for full details of the BCM2835 controller:
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https://www.raspberrypi.org/documentation/hardware/raspberrypi/bcm2835/BCM2835-ARM-Peripherals.pdf
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and https://elinux.org/BCM2835_datasheet_errata - for errors in that spec
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Changes to support the BCM2711, used on the Raspberry Pi 4, were cribbed from https://github.com/RPi-Distro/raspi-gpio/
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*/
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package rpio
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import (
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"bytes"
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"encoding/binary"
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"errors"
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"os"
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"reflect"
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"sync"
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@ -95,6 +98,14 @@ const (
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memLength = 4096
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)
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// BCM 2711 has a different mechanism for pull-up/pull-down/enable
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const (
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GPPUPPDN0 = 57 // Pin pull-up/down for pins 15:0
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GPPUPPDN1 = 58 // Pin pull-up/down for pins 31:16
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GPPUPPDN2 = 59 // Pin pull-up/down for pins 47:32
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GPPUPPDN3 = 60 // Pin pull-up/down for pins 57:48
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)
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var (
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gpioBase int64
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clkBase int64
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@ -134,6 +145,7 @@ const (
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PullOff Pull = iota
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PullDown
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PullUp
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PullNone
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)
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// Edge events
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@ -239,6 +251,25 @@ func (pin Pin) PullOff() {
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PullMode(pin, PullOff)
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}
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func (pin Pin) ReadPull() Pull {
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if !isBCM2711() {
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return PullNone // Can't read pull-up/pull-down state on other Pi boards
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}
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reg := GPPUPPDN0 + (uint8(pin) >> 4)
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bits := gpioMem[reg] >> ((uint8(pin) & 0xf) << 1) & 0x3
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switch bits {
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case 0:
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return PullOff
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case 1:
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return PullUp
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case 2:
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return PullDown
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default:
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return PullNone // Invalid
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}
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}
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// Detect: Enable edge event detection on pin
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func (pin Pin) Detect(edge Edge) {
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DetectEdge(pin, edge)
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@ -429,32 +460,54 @@ func EdgeDetected(pin Pin) bool {
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}
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func PullMode(pin Pin, pull Pull) {
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// Pull up/down/off register has offset 38 / 39, pull is 37
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pullClkReg := pin/32 + 38
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pullReg := 37
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shift := pin % 32
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memlock.Lock()
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defer memlock.Unlock()
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switch pull {
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case PullDown, PullUp:
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gpioMem[pullReg] |= uint32(pull)
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case PullOff:
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if isBCM2711() {
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pullreg := GPPUPPDN0 + (pin >> 4)
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pullshift := (pin & 0xf) << 1
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var p uint32
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switch pull {
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case PullOff:
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p = 0
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case PullUp:
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p = 1
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case PullDown:
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p = 2;
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}
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// This is verbatim C code from raspi-gpio.c
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pullbits := gpioMem[pullreg]
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pullbits &= ^(3 << pullshift)
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pullbits |= (p << pullshift)
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gpioMem[pullreg]= pullbits
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} else {
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// Pull up/down/off register has offset 38 / 39, pull is 37
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pullClkReg := pin/32 + 38
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pullReg := 37
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shift := pin % 32
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switch pull {
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case PullDown, PullUp:
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gpioMem[pullReg] |= uint32(pull)
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case PullOff:
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gpioMem[pullReg] &^= 3
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}
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// Wait for value to clock in, this is ugly, sorry :(
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time.Sleep(time.Microsecond)
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gpioMem[pullClkReg] = 1 << shift
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// Wait for value to clock in
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time.Sleep(time.Microsecond)
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gpioMem[pullReg] &^= 3
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gpioMem[pullClkReg] = 0
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}
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// Wait for value to clock in, this is ugly, sorry :(
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time.Sleep(time.Microsecond)
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gpioMem[pullClkReg] = 1 << shift
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// Wait for value to clock in
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time.Sleep(time.Microsecond)
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gpioMem[pullReg] &^= 3
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gpioMem[pullClkReg] = 0
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}
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// SetFreq: Set clock speed for given pin in Clock or Pwm mode
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@ -714,23 +767,49 @@ func Close() error {
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// Read /proc/device-tree/soc/ranges and determine the base address.
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// Use the default Raspberry Pi 1 base address if this fails.
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func getBase() (base int64) {
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base = bcm2835Base
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func readBase(offset int64) (int64, error) {
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ranges, err := os.Open("/proc/device-tree/soc/ranges")
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defer ranges.Close()
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if err != nil {
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return
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return 0, err
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}
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b := make([]byte, 4)
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n, err := ranges.ReadAt(b, 4)
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n, err := ranges.ReadAt(b, offset)
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if n != 4 || err != nil {
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return
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return 0, err
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}
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buf := bytes.NewReader(b)
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var out uint32
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err = binary.Read(buf, binary.BigEndian, &out)
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if err != nil {
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return
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return 0, err
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}
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return int64(out)
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if out == 0 {
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return 0, errors.New("rpio: GPIO base address not found")
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}
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return int64(out), nil
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}
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func getBase() int64 {
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// Pi 2 & 3 GPIO base address is at offset 4
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b, err := readBase(4)
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if err == nil {
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return b
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}
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// Pi 4 GPIO base address is as offset 8
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b, err = readBase(8)
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if err == nil {
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return b
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}
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// Default to Pi 1
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return int64(bcm2835Base)
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}
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// The Pi 4 uses a BCM 2711, which has different register offsets and base addresses than the rest of the Pi family (so far). This
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// helper function checks if we're on a 2711 and hence a Pi 4
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func isBCM2711() bool {
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return gpioMem[GPPUPPDN3] != 0x6770696f
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}
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