diff --git a/examples/pwmbalanced/pwm.go b/examples/pwmbalanced/pwm.go new file mode 100644 index 0000000..7a0841c --- /dev/null +++ b/examples/pwmbalanced/pwm.go @@ -0,0 +1,44 @@ +/* + +A PWM example by @youngkin, using the go-rpio library + +Fades a PWM hardware pin in and out using PWM mode balanced (vs. markspace) +*/ + +package main + +import ( + "os" + "time" + + "github.com/stianeikeland/go-rpio/v4" +) + +func main() { + err := rpio.Open() + if err != nil { + os.Exit(1) + } + defer rpio.Close() + + pin := rpio.Pin(19) + pin.Mode(rpio.Pwm) + pin.Freq(64000) + pin.DutyCycleWithPwmMode(0, 32, rpio.Balanced) + // the LED will be blinking at 2000Hz + // (source frequency divided by cycle length => 64000/32 = 2000) + + // five times smoothly fade in and out + for i := 0; i < 5; i++ { + for i := uint32(0); i < 32; i++ { // increasing brightness + pin.DutyCycleWithPwmMode(i, 32, rpio.Balanced) + time.Sleep(time.Second / 32) + } + for i := uint32(32); i > 0; i-- { // decreasing brightness + pin.DutyCycleWithPwmMode(i, 32, rpio.Balanced) + time.Sleep(time.Second / 32) + } + } + + pin.DutyCycleWithPwmMode(0, 32, rpio.Balanced) +} diff --git a/rpio.go b/rpio.go index 04a42a5..557e993 100644 --- a/rpio.go +++ b/rpio.go @@ -3,31 +3,31 @@ Package rpio provides GPIO access on the Raspberry PI without any need for external c libraries (eg. WiringPi or BCM2835). Supports simple operations such as: - - Pin mode/direction (input/output/clock/pwm,alt0,alt1,alt2,alt3,alt4,alt5) - - Pin write (high/low) - - Pin read (high/low) - - Pin edge detection (no/rise/fall/any) - - Pull up/down/off + - Pin mode/direction (input/output/clock/pwm,alt0,alt1,alt2,alt3,alt4,alt5) + - Pin write (high/low) + - Pin read (high/low) + - Pin edge detection (no/rise/fall/any) + - Pull up/down/off Also clock/pwm related oparations: - - Set Clock frequency - - Set Duty cycle + - Set Clock frequency + - Set Duty cycle And SPI oparations: - - SPI transmit/recieve/exchange bytes - - Chip select - - Set speed + - SPI transmit/recieve/exchange bytes + - Set speed + - Chip select Example of use: - rpio.Open() - defer rpio.Close() + rpio.Open() + defer rpio.Close() - pin := rpio.Pin(4) - pin.Output() + pin := rpio.Pin(4) + pin.Output() - for { - pin.Toggle() - time.Sleep(time.Second) - } + for { + pin.Toggle() + time.Sleep(time.Second) + } The library use the raw BCM2835 pinouts, not the ports as they are mapped on the output pins for the raspberry pi, and not the wiringPi convention. @@ -100,10 +100,10 @@ const ( // BCM 2711 has a different mechanism for pull-up/pull-down/enable const ( - GPPUPPDN0 = 57 // Pin pull-up/down for pins 15:0 - GPPUPPDN1 = 58 // Pin pull-up/down for pins 31:16 - GPPUPPDN2 = 59 // Pin pull-up/down for pins 47:32 - GPPUPPDN3 = 60 // Pin pull-up/down for pins 57:48 + GPPUPPDN0 = 57 // Pin pull-up/down for pins 15:0 + GPPUPPDN1 = 58 // Pin pull-up/down for pins 31:16 + GPPUPPDN2 = 59 // Pin pull-up/down for pins 47:32 + GPPUPPDN3 = 60 // Pin pull-up/down for pins 57:48 ) var ( @@ -146,6 +146,12 @@ const ( High ) +// Which PWM algorithm to use, Balanced or Mark/Space +const ( + Balanced = true + MarkSpace = false +) + // Pull Up / Down / Off const ( PullOff Pull = iota @@ -222,6 +228,12 @@ func (pin Pin) DutyCycle(dutyLen, cycleLen uint32) { SetDutyCycle(pin, dutyLen, cycleLen) } +// DutyCycleWithPwmMode: Set duty cycle for Pwm pin while also specifying which PWM +// mode to use, Balanced or MarkSpace (see doc of SetDutyCycleWithPwmMode) +func (pin Pin) DutyCycleWithPwmMode(dutyLen, cycleLen uint32, mode bool) { + SetDutyCycleWithPwmMode(pin, dutyLen, cycleLen, mode) +} + // Mode: Set pin Mode func (pin Pin) Mode(mode Mode) { PinMode(pin, mode) @@ -259,7 +271,7 @@ func (pin Pin) PullOff() { func (pin Pin) ReadPull() Pull { if !isBCM2711() { - return PullNone // Can't read pull-up/pull-down state on other Pi boards + return PullNone // Can't read pull-up/pull-down state on other Pi boards } reg := GPPUPPDN0 + (uint8(pin) >> 4) @@ -272,7 +284,7 @@ func (pin Pin) ReadPull() Pull { case 2: return PullDown default: - return PullNone // Invalid + return PullNone // Invalid } } @@ -481,51 +493,51 @@ func EdgeDetected(pin Pin) bool { } func PullMode(pin Pin, pull Pull) { - + memlock.Lock() defer memlock.Unlock() if isBCM2711() { pullreg := GPPUPPDN0 + (pin >> 4) pullshift := (pin & 0xf) << 1 - - var p uint32 - + + var p uint32 + switch pull { case PullOff: p = 0 case PullUp: p = 1 case PullDown: - p = 2; + p = 2 } - + // This is verbatim C code from raspi-gpio.c pullbits := gpioMem[pullreg] pullbits &= ^(3 << pullshift) pullbits |= (p << pullshift) - gpioMem[pullreg]= pullbits + gpioMem[pullreg] = pullbits } else { // Pull up/down/off register has offset 38 / 39, pull is 37 pullClkReg := pin/32 + 38 pullReg := 37 shift := pin % 32 - + switch pull { case PullDown, PullUp: gpioMem[pullReg] |= uint32(pull) case PullOff: gpioMem[pullReg] &^= 3 } - + // Wait for value to clock in, this is ugly, sorry :( time.Sleep(time.Microsecond) - + gpioMem[pullClkReg] = 1 << shift - + // Wait for value to clock in time.Sleep(time.Microsecond) - + gpioMem[pullReg] &^= 3 gpioMem[pullClkReg] = 0 } @@ -550,7 +562,7 @@ func SetFreq(pin Pin, freq int) { if isBCM2711() { sourceFreq = 52000000 } - const divMask = 4095 // divi and divf have 12 bits each + const divMask = 4095 // divi and divf have 12 bits each divi := uint32(sourceFreq / freq) divf := uint32(((sourceFreq % freq) << 12) / freq) @@ -627,12 +639,26 @@ func SetFreq(pin Pin, freq int) { // The channels are: // channel 1 (pwm0) for pins 12, 18, 40 // channel 2 (pwm1) for pins 13, 19, 41, 45. +// +// NOTE without root permission this function will simply do nothing successfully func SetDutyCycle(pin Pin, dutyLen, cycleLen uint32) { + SetDutyCycleWithPwmMode(pin, dutyLen, cycleLen, MarkSpace) + +} + +// SetDutyCycleWithPwmMode extends SetDutyCycle to allow for the specification of the PWM +// algorithm to be used, Balanced or Mark/Space. The constants Balanced or MarkSpace +// as the value. See 'SetDutyCycle(pin, dutyLen, cycleLen)' above for more information +// regarding how to use 'SetDutyCycleWithPwmMode()'. +// +// NOTE without root permission this function will simply do nothing successfully +func SetDutyCycleWithPwmMode(pin Pin, dutyLen, cycleLen uint32, mode bool) { const pwmCtlReg = 0 var ( pwmDatReg uint pwmRngReg uint shift uint // offset inside ctlReg + ) switch pin { @@ -646,20 +672,29 @@ func SetDutyCycle(pin Pin, dutyLen, cycleLen uint32) { 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 + var msen uint32 = 0 + // The MSEN1 field in the CTL register is at offset 7. This block starts with the assumption + // that 'msen' will be associated with channel 'pwm0'. If this is not the case, 'msen' will + // be further shifted in the next code block below to the MSEN2 field at offset 15. + if mode == MarkSpace { + msen = 1 << 7 + } - // reset settings + // Shifting 'pwen' and 'msen' puts the associated values at the correct offset within the CTL + // register ('pwmCtlReg'). In addition, 'msen' is associated with a PWM channel depending on the + // value of 'pin' (see above). 'msen' will either stay at offset 7, as set above for channel 'pwm0', + // or be shifted 8 bits if the the associated 'pin' is on channel 'pwm1'. pwmMem[pwmCtlReg] = pwmMem[pwmCtlReg]&^(ctlMask<