go-packages/go-rpio
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address code review comments

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youngkin 2021-12-01 21:22:34 +00:00
parent 02c0360e26
commit 915fc229cf
1 changed files with 73 additions and 62 deletions
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49
rpio.go
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@ -60,8 +60,8 @@ on the output pins for the raspberry pi, and not the wiringPi convention.
See the spec for full details of the BCM2835 controller:
https://www.raspberrypi.org/documentation/hardware/raspberrypi/bcm2835/BCM2835-ARM-Peripherals.pdf
and https://elinux.org/BCM2835_datasheet_errata - for errors in that spec
https://www.raspberrypi.org/documentation/hardware/raspberrypi/bcm2835/BCM2835-ARM-Peripherals.pdf
and https://elinux.org/BCM2835_datasheet_errata - for errors in that spec
Changes to support the BCM2711, used on the Raspberry Pi 4, were cribbed from https://github.com/RPi-Distro/raspi-gpio/
@ -148,8 +148,8 @@ const (
// Which PWM algorithm to use, Balanced or Mark/Space
const (
Balanced = iota
MarkSpace
Balanced = true
MarkSpace = false
)
// Pull Up / Down / Off
@ -228,9 +228,10 @@ func (pin Pin) DutyCycle(dutyLen, cycleLen uint32) {
SetDutyCycle(pin, dutyLen, cycleLen)
}
// DutyCycleMsen: Set duty cycle for Pwm pin (see doc of SetDutyCycle)
func (pin Pin) DutyCycleMsen(dutyLen, cycleLen, msen uint32) {
SetDutyCycleMsen(pin, dutyLen, cycleLen, msen)
// 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
@ -638,17 +639,20 @@ 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) {
SetDutyCycleMsen(pin, dutyLen, cycleLen, 1) // Default PWM algorithm is Mark/Space, msen = 1
SetDutyCycleWithPwmMode(pin, dutyLen, cycleLen, MarkSpace)
}
// SetDutyCycleMsen extends SetDutyCycle to allow for the specification of the PWM
// algorithm to be used, Balanced or Mark/Space. 'msen' is used to indicate which
// PWM algorithm to use. The constants Balanced or Markspace should be used as the
// value. See 'SetDutyCycle(pin, dutyLen, cycleLen)' above for more information
// regarding how to use 'SetDutyCycleMsen()'
func SetDutyCycleMsen(pin Pin, dutyLen, cycleLen, msen uint32) {
// 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
@ -673,17 +677,24 @@ func SetDutyCycleMsen(pin Pin, dutyLen, cycleLen, msen uint32) {
const ctlMask = 255 // ctl setting has 8 bits for each channel
const pwen = 1 << 0 // enable pwm
msen = msen << 7
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<<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
}
// StopPwm: Stop pwm for both channels