Merge pull request #1 from Drahoslav7/pwm

Pwm

rpio.go

@@ -1,13 +1,15 @@
 /*
-
 Package rpio provides GPIO access on the Raspberry PI without any need
-for external c libraries (ex: WiringPI or BCM2835).
+for external c libraries (eg. WiringPi or BCM2835).
 
 Supports simple operations such as:
-- Pin mode/direction (input/output/clock)
+	- Pin mode/direction (input/output/clock/pwm)
-- Pin write (high/low)
+	- Pin write (high/low)
-- Pin read (high/low)
+	- Pin read (high/low)
-- Pull up/down/off
+	- Pull up/down/off
+And clock/pwm related oparations:
+	- Set Clock frequency
+	- Set Duty cycle
 
 Example of use:
 
@@ -23,36 +25,40 @@ Example of use:
 	}
 
 The library use the raw BCM2835 pinouts, not the ports as they are mapped
-on the output pins for the raspberry pi
+on the output pins for the raspberry pi, and not the wiringPi convention.
 
-   Rev 1 Raspberry Pi
+            Rev 2 and 3 Raspberry Pi                        Rev 1 Raspberry Pi (legacy)
-+------+------+--------+
+  +-----+---------+----------+---------+-----+      +-----+--------+----------+--------+-----+
-| GPIO | Phys | Name   |
+  | BCM |   Name  | Physical | Name    | BCM |      | BCM | Name   | Physical | Name   | BCM |
-+------+------+--------+
+  +-----+---------+----++----+---------+-----+      +-----+--------+----++----+--------+-----+
-|   0  |   3  | SDA    |
+  |     |    3.3v |  1 || 2  | 5v      |     |      |     | 3.3v   |  1 ||  2 | 5v     |     |
-|   1  |   5  | SCL    |
+  |   2 |   SDA 1 |  3 || 4  | 5v      |     |      |   0 | SDA    |  3 ||  4 | 5v     |     |
-|   4  |   7  | GPIO 7 |
+  |   3 |   SCL 1 |  5 || 6  | 0v      |     |      |   1 | SCL    |  5 ||  6 | 0v     |     |
-|   7  |  26  | CE1    |
+  |   4 | GPIO  7 |  7 || 8  | TxD     | 14  |      |   4 | GPIO 7 |  7 ||  8 | TxD    |  14 |
-|   8  |  24  | CE0    |
+  |     |      0v |  9 || 10 | RxD     | 15  |      |     | 0v     |  9 || 10 | RxD    |  15 |
-|   9  |  21  | MISO   |
+  |  17 | GPIO  0 | 11 || 12 | GPIO  1 | 18  |      |  17 | GPIO 0 | 11 || 12 | GPIO 1 |  18 |
-|  10  |  19  | MOSI   |
+  |  27 | GPIO  2 | 13 || 14 | 0v      |     |      |  21 | GPIO 2 | 13 || 14 | 0v     |     |
-|  11  |  23  | SCLK   |
+  |  22 | GPIO  3 | 15 || 16 | GPIO  4 | 23  |      |  22 | GPIO 3 | 15 || 16 | GPIO 4 |  23 |
-|  14  |   8  | TxD    |
+  |     |    3.3v | 17 || 18 | GPIO  5 | 24  |      |     | 3.3v   | 17 || 18 | GPIO 5 |  24 |
-|  15  |  10  | RxD    |
+  |  10 |    MOSI | 19 || 20 | 0v      |     |      |  10 | MOSI   | 19 || 20 | 0v     |     |
-|  17  |  11  | GPIO 0 |
+  |   9 |    MISO | 21 || 22 | GPIO  6 | 25  |      |   9 | MISO   | 21 || 22 | GPIO 6 |  25 |
-|  18  |  12  | GPIO 1 |
+  |  11 |    SCLK | 23 || 24 | CE0     | 8   |      |  11 | SCLK   | 23 || 24 | CE0    |   8 |
-|  21  |  13  | GPIO 2 |
+  |     |      0v | 25 || 26 | CE1     | 7   |      |     | 0v     | 25 || 26 | CE1    |   7 |
-|  22  |  15  | GPIO 3 |
+  |   0 |   SDA 0 | 27 || 28 | SCL 0   | 1   |      +-----+--------+----++----+--------+-----+
-|  23  |  16  | GPIO 4 |
+  |   5 | GPIO 21 | 29 || 30 | 0v      |     |
-|  24  |  18  | GPIO 5 |
+  |   6 | GPIO 22 | 31 || 32 | GPIO 26 | 12  |
-|  25  |  22  | GPIO 6 |
+  |  13 | GPIO 23 | 33 || 34 | 0v      |     |
-+------+------+--------+
+  |  19 | GPIO 24 | 35 || 36 | GPIO 27 | 16  |
+  |  26 | GPIO 25 | 37 || 38 | GPIO 28 | 20  |
+  |     |      0v | 39 || 40 | GPIO 29 | 21  |
+  +-----+---------+----++----+---------+-----+
 
 See the spec for full details of the BCM2835 controller:
-http://www.raspberrypi.org/wp-content/uploads/2012/02/BCM2835-ARM-Peripherals.pdf
+
+https://www.raspberrypi.org/documentation/hardware/raspberrypi/bcm2835/BCM2835-ARM-Peripherals.pdf
+and https://elinux.org/BCM2835_datasheet_errata - for errors in that spec
 
 */
-
 package rpio
 
 import (
@@ -76,6 +82,7 @@ const (
 	bcm2835Base = 0x20000000
 	gpioOffset  = 0x200000
 	clkOffset   = 0x101000
+	pwmOffset   = 0x20C000
 
 	memLength = 4096
 )
@@ -83,19 +90,22 @@ const (
 var (
 	gpioBase int64
 	clkBase  int64
+	pwmBase  int64
 )
 
 func init() {
 	base := getBase()
 	gpioBase = base + gpioOffset
 	clkBase = base + clkOffset
+	pwmBase = base + pwmOffset
 }
 
-// Pin mode, a pin can be set in Input or Output mode, or clock
+// Pin mode, a pin can be set in Input or Output, Clock or Pwm mode
 const (
 	Input Mode = iota
 	Output
 	Clock
+	Pwm
 )
 
 // State of pin, High / Low
@@ -116,8 +126,10 @@ var (
 	memlock  sync.Mutex
 	gpioMem  []uint32
 	clkMem   []uint32
+	pwmMem   []uint32
 	gpioMem8 []uint8
 	clkMem8  []uint8
+	pwmMem8  []uint8
 )
 
 // Set pin as Input
@@ -135,6 +147,11 @@ func (pin Pin) Clock() {
 	PinMode(pin, Clock)
 }
 
+// Set pin as Pwm
+func (pin Pin) Pwm() {
+	PinMode(pin, Pwm)
+}
+
 // Set pin High
 func (pin Pin) High() {
 	WritePin(pin, High)
@@ -150,10 +167,16 @@ func (pin Pin) Toggle() {
 	TogglePin(pin)
 }
 
+// Set frequency of Clock or Pwm pin (see doc of SetFreq)
 func (pin Pin) Freq(freq int) {
 	SetFreq(pin, freq)
 }
 
+// Set duty cycle for Pwm pin (see doc of SetDutyCycle)
+func (pin Pin) DutyCycle(dutyLen, cycleLen uint32) {
+	SetDutyCycle(pin, dutyLen, cycleLen)
+}
+
 // Set pin Mode
 func (pin Pin) Mode(mode Mode) {
 	PinMode(pin, mode)
@@ -189,9 +212,10 @@ func (pin Pin) PullOff() {
 	PullMode(pin, PullOff)
 }
 
-// PinMode sets the mode (direction) of a given pin (Input, Output or Clock)
+// PinMode sets the mode (direction) of a given pin (Input, Output, Clock or Pwm)
 //
-// Clock is possible only for some pins (bcm 4, 5, 6, 20, 21)
+// Clock is possible only for pins 4, 5, 6, 20, 21.
+// Pwm is possible only for pins 12, 13, 18, 19.
 func PinMode(pin Pin, mode Mode) {
 
 	// Pin fsel register, 0 or 1 depending on bank
@@ -199,6 +223,9 @@ func PinMode(pin Pin, mode Mode) {
 	shift := (uint8(pin) % 10) * 3
 	f := uint32(0)
 
+	const alt0 = 4 // 100
+	const alt5 = 2 // 010
+
 	switch mode {
 	case Input:
 		f = 0 // 000
@@ -207,9 +234,18 @@ func PinMode(pin Pin, mode Mode) {
 	case Clock:
 		switch pin {
 		case 4, 5, 6, 32, 34, 42, 43, 44:
-			f = 4 // 100 - alt0
+			f = alt0
 		case 20, 21:
-			f = 2 // 010 - alt5
+			f = alt5
+		default:
+			return
+		}
+	case Pwm:
+		switch pin {
+		case 12, 13, 40, 41, 45:
+			f = alt0
+		case 18, 19:
+			f = alt5
 		default:
 			return
 		}
@@ -270,9 +306,9 @@ func TogglePin(pin Pin) {
 
 func PullMode(pin Pin, pull Pull) {
 	// Pull up/down/off register has offset 38 / 39, pull is 37
-	pullClkReg := uint8(pin)/32 + 38
+	pullClkReg := pin/32 + 38
 	pullReg := 37
-	shift := (uint8(pin) % 32)
+	shift := pin % 32
 
 	memlock.Lock()
 	defer memlock.Unlock()
@@ -297,37 +333,47 @@ func PullMode(pin Pin, pull Pull) {
 
 }
 
-// Set clock speed for given pin
+// Set clock speed for given pin in Clock or Pwm mode
 //
-// freq should be in range 4688Hz - 19.2MHz to prevent unexpected behavior
+// Param freq should be in range 4688Hz - 19.2MHz to prevent unexpected behavior,
-// (for smaller frequencies implement custom software clock using output pin and sleep)
+// however output frequency of Pwm pins can be further adjusted with SetDutyCycle.
+// So for smaller frequencies use Pwm pin with large cycle range. (Or implement custom software clock using output pin and sleep.)
 //
 // Note that some pins share the same clock source, it means that
-// changing frequency for one pin will change it also for all pins within a group
+// changing frequency for one pin will change it also for all pins within a group.
-// The groups are: clk0 (4, 20, 32, 34), clk1 (5, 21, 42, 43) and clk2 (6 and 43)
+// The groups are:
+//   gp_clk0: pins 4, 20, 32, 34
+//   gp_clk1: pins 5, 21, 42, 43
+//   gp_clk2: pins 6 and 43
+//   pwm_clk: pins 12, 13, 18, 19, 40, 41, 45
 func SetFreq(pin Pin, freq int) {
 	// TODO: would be nice to choose best clock source depending on target frequency, oscilator is used for now
 	const sourceFreq = 19200000 // oscilator frequency
-	const maxUint12 = 4095
+	const divMask = 4095        // divi and divf have 12 bits each
 
 	divi := uint32(sourceFreq / freq)
 	divf := uint32(((sourceFreq % freq) << 12) / freq)
 
-	divi &= maxUint12
+	divi &= divMask
-	divf &= maxUint12
+	divf &= divMask
 
 	clkCtlReg := 28
-	clkDivReg := 29
+	clkDivReg := 28
 	switch pin {
 	case 4, 20, 32, 34: // clk0
 		clkCtlReg += 0
-		clkDivReg += 0
+		clkDivReg += 1
 	case 5, 21, 42, 44: // clk1
 		clkCtlReg += 2
-		clkDivReg += 2
+		clkDivReg += 3
 	case 6, 43: // clk2
 		clkCtlReg += 4
-		clkDivReg += 4
+		clkDivReg += 5
+	case 12, 13, 40, 41, 45, 18, 19: // pwm_clk - shared clk for both pwm channels
+		clkCtlReg += 12
+		clkDivReg += 13
+		StopPwm() // pwm clk busy wont go down without stopping pwm first
+		defer StartPwm()
 	default:
 		return
 	}
@@ -361,6 +407,74 @@ func SetFreq(pin Pin, freq int) {
 	// NOTE without root permission this changes will simply do nothing successfully
 }
 
+// Set cycle length (range) and duty length (data) for Pwm pin in M/S mode
+//
+//   |<- duty ->|
+//    __________
+//  _/          \_____________/
+//   |<------- cycle -------->|
+//
+// Output frequency is computed as pwm clock frequency divided by cycle length.
+// So, to set Pwm pin to freqency 38kHz with duty cycle 1/4, use this combination:
+//
+//  pin.Pwm()
+//  pin.DutyCycle(1, 4)
+//  pin.Freq(38000*4)
+//
+// Note that some pins share common pwm channel,
+// so calling this function will set same duty cycle for all pins belonging to channel.
+// The channels are:
+//   channel 1 (pwm0) for pins 12, 18, 40
+//   channel 2 (pwm1) for pins 13, 19, 41, 45.
+func SetDutyCycle(pin Pin, dutyLen, cycleLen uint32) {
+	const pwmCtlReg = 0
+	var (
+		pwmDatReg uint
+		pwmRngReg uint
+		shift     uint // offset inside ctlReg
+	)
+
+	switch pin {
+	case 12, 18, 40: // channel pwm0
+		pwmRngReg = 4
+		pwmDatReg = 5
+		shift = 0
+	case 13, 19, 41, 45: // channel pwm1
+		pwmRngReg = 8
+		pwmDatReg = 9
+		shift = 8
+	default:
+		return
+	}
+
+	const ctlMask = 255 // ctl setting has 8 bits for each channel
+	const pwen = 1 << 0 // enable pwm
+	const msen = 1 << 7 // use M/S transition instead of pwm algorithm
+
+	// reset settings
+	pwmMem[pwmCtlReg] = pwmMem[pwmCtlReg]&^(ctlMask<<shift) | msen<<shift | pwen <<shift
+	// set duty cycle
+	pwmMem[pwmDatReg] = dutyLen
+	pwmMem[pwmRngReg] = cycleLen
+	time.Sleep(time.Microsecond * 10)
+
+	// NOTE without root permission this changes will simply do nothing successfully
+}
+
+// Stop pwm for both channels
+func StopPwm() {
+	const pwmCtlReg = 0
+	const pwen = 1
+	pwmMem[pwmCtlReg] = pwmMem[pwmCtlReg] &^ (pwen<<8 | pwen)
+}
+
+// Start pwm for both channels
+func StartPwm() {
+	const pwmCtlReg = 0
+	const pwen = 1
+	pwmMem[pwmCtlReg] = pwmMem[pwmCtlReg] | pwen<<8 | pwen
+}
+
 // Open and memory map GPIO memory range from /dev/mem .
 // Some reflection magic is used to convert it to a unsafe []uint32 pointer
 func Open() (err error) {
@@ -368,7 +482,7 @@ func Open() (err error) {
 
 	// Open fd for rw mem access; try dev/mem first (need root)
 	file, err = os.OpenFile("/dev/mem", os.O_RDWR|os.O_SYNC, 0)
-	if os.IsPermission(err) { // try gpiomem otherwise (some extra functions like clock setting wont work)
+	if os.IsPermission(err) { // try gpiomem otherwise (some extra functions like clock and pwm setting wont work)
 		file, err = os.OpenFile("/dev/gpiomem", os.O_RDWR|os.O_SYNC, 0)
 	}
 	if err != nil {
@@ -392,6 +506,11 @@ func Open() (err error) {
 		return
 	}
 
+	pwmMem, pwmMem8, err = memMap(file.Fd(), pwmBase)
+	if err != nil {
+		return
+	}
+
 	return nil
 }