/
pca9685.go
112 lines (98 loc) · 2.73 KB
/
pca9685.go
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package pca9685
import (
"log"
"math"
"time"
"github.com/reef-pi/rpi/i2c"
)
const (
clockFreq = 25000000
pwmControlPoints = 4096
mode1RegAddr = 0x00
preScaleRegAddr = 0xFE
pwm0OnLowReg = 0x6
defaultFreq = 490
)
type PCA9685 struct {
addr byte
bus i2c.Bus
Freq int
}
func New(addr byte, bus i2c.Bus) *PCA9685 {
return &PCA9685{
addr: addr,
bus: bus,
Freq: defaultFreq,
}
}
func (p *PCA9685) mode1Reg() (byte, error) {
mode1Reg := make([]byte, 1)
return mode1Reg[0], p.bus.WriteToReg(p.addr, mode1RegAddr, mode1Reg)
}
// Set the sleep flag on the PCA. This will shut down the oscillators.
func (p *PCA9685) Sleep() error {
mode1Reg, err := p.mode1Reg()
if err != nil {
return err
}
sleepmode := (mode1Reg & 0x7F) | 0x10 // Mask restart bit and set sleep bit
return p.bus.WriteToReg(p.addr, mode1RegAddr, []byte{sleepmode})
}
func (p *PCA9685) Wake() error {
mode1Reg, err := p.mode1Reg()
if err != nil {
return err
}
if err := p.Sleep(); err != nil {
return err
}
if p.Freq == 0 {
p.Freq = defaultFreq
}
preScaleValue := byte(math.Floor(float64(clockFreq/(pwmControlPoints*p.Freq))+float64(0.5)) - 1)
if err := p.bus.WriteToReg(p.addr, preScaleRegAddr, []byte{preScaleValue}); err != nil {
return err
}
wakeMode := mode1Reg & 0xEF
if (mode1Reg & 0x80) == 0x80 {
if err := p.bus.WriteToReg(p.addr, mode1RegAddr, []byte{wakeMode}); err != nil {
return err
}
time.Sleep(500 * time.Microsecond)
}
restartOpCode := wakeMode | 0x80
if err := p.bus.WriteToReg(p.addr, mode1RegAddr, []byte{restartOpCode}); err != nil {
return err
}
newmode := ((mode1Reg | 0x01) & 0xDF)
return p.bus.WriteToReg(p.addr, mode1RegAddr, []byte{newmode})
}
func (p *PCA9685) SetPwm(channel int, onTime, offTime uint16) error {
log.Println("onTime ", onTime, " offTime ", offTime)
// Split the ints into 4 bytes
timeReg := byte(pwm0OnLowReg + (4 * channel))
onTimeLow := byte(onTime & 0xFF)
onTimeHigh := byte(onTime >> 8)
offTimeLow := byte(offTime & 0xFF)
offTimeHigh := byte(offTime >> 8)
//log.Println("onLow ", onTimeLow, " onHigh ", onTimeHigh, " offLow ", offTimeLow, " offHigh ", offTimeHigh)
if err := p.bus.WriteToReg(p.addr, timeReg, []byte{onTimeLow}); err != nil {
return err
}
if err := p.bus.WriteToReg(p.addr, timeReg+1, []byte{onTimeHigh}); err != nil {
return err
}
if err := p.bus.WriteToReg(p.addr, timeReg+2, []byte{offTimeLow}); err != nil {
return err
}
return p.bus.WriteToReg(p.addr, timeReg+3, []byte{offTimeHigh})
}
func (p *PCA9685) Close() error {
// Clear all channels to full off
for regAddr := 0x06; regAddr < 0x50; regAddr += 4 {
if err := p.bus.WriteToReg(p.addr, byte(regAddr), []byte{0x00, 0x00, 0x00, 0x10}); err != nil {
return err
}
}
return nil
}