Rework GPIO function setting to be a bit nicer. Add functions for set…

…ting pins as inputs, outputs, including compulsory specification of pull up/down/none mode for outputs.

rpi/gpio.go

@@ -3,6 +3,7 @@ package rpi
 import (
  "fmt"
  "log"
+ "time"
  "unsafe"
 )
 
@@ -35,17 +36,57 @@ type gpioT struct {
  test uint32
 }
 
-func (rp *RPi) gpioFunctionSet(pin int, alt int) error {
+type PullMode uint
+
+const (
+ // See p101. These are GPPUD values
+ PullNone = 0
+ PullDown = 1
+ PullUp = 2
+)
+
+func (rp *RPi) gpioSetPinFunction(pin int, fnc uint32) error {
+ if pin > 53 { // p94
+ return fmt.Errorf("pin %d not supported")
+ }
  reg := pin / 10
  offset := uint((pin % 10) * 3)
+ rp.gpio.fsel[reg] &= ^(0x7 << offset)
+ rp.gpio.fsel[reg] |= fnc << offset
+ return nil
+}
+
+func (rp *RPi) gpioSetInput(pin int) error {
+ return rp.gpioSetPinFunction(pin, 0)
+}
+
+func (rp *RPi) gpioSetOutput(pin int, pm PullMode) error {
+ if pm > PullUp {
+ return fmt.Errorf("%d is an invalid pull mode", pm)
+ }
+ err := rp.gpioSetPinFunction(pin, 1)
+ if err != nil {
+ return fmt.Errorf("couldn't set pin as output: %v", err)
+ }
+
+ // See p101 for the description of this procedure.
+ rp.gpio.pud = uint32(pm)
+ time.Sleep(10 * time.Microsecond) // Datasheet says to sleep for 150 cycles after setting pud
+ reg := pin / 32
+ offset := uint(pin % 32)
+ rp.gpio.pudclk[reg] = 1 << offset
+ time.Sleep(10 * time.Microsecond) // Datasheet says to sleep for 150 cycles after setting pudclk
+ rp.gpio.pud = 0
+ rp.gpio.pudclk[reg] = 0
+ return nil
+}
+
+func (rp *RPi) gpioSetAltFunction(pin int, alt int) error {
  funcs := []uint32{4, 5, 6, 7, 3, 2} // See p92 in datasheet - these are the alt functions only
  if alt >= len(funcs) {
  return fmt.Errorf("%d is an invalid alt function", alt)
  }
-
- rp.gpio.fsel[reg] &= ^(0x7 << offset)
- rp.gpio.fsel[reg] |= (funcs[alt]) << offset
- return nil
+ return rp.gpioSetPinFunction(pin, funcs[alt])
 }
 
 func (rp *RPi) InitGPIO() error {

rpi/pwm.go

@@ -74,7 +74,7 @@ func (rp *RPi) InitPWM(freq uint, buf *DMABuf, bytes uint, pins []int) error {
  if !ok {
  return fmt.Errorf("invalid pin %d for PWM channel %d", pin, channel)
  }
- rp.gpioFunctionSet(pin, alt)
+ rp.gpioSetAltFunction(pin, alt)
  }
 
  if rp.pwmBuf == nil {