Implement basic SPI

rpio.go

@@ -85,6 +85,7 @@ const (
 	gpioOffset  = 0x200000
 	clkOffset   = 0x101000
 	pwmOffset   = 0x20C000
+	spiOffset   = 0x204000
 
 	memLength = 4096
 )
@@ -93,6 +94,7 @@ var (
 	gpioBase int64
 	clkBase  int64
 	pwmBase  int64
+	spiBase  int64
 )
 
 func init() {
@@ -100,6 +102,7 @@ func init() {
 	gpioBase = base + gpioOffset
 	clkBase = base + clkOffset
 	pwmBase = base + pwmOffset
+	spiBase = base + spiOffset
 }
 
 // Pin mode, a pin can be set in Input or Output, Clock or Pwm mode
@@ -108,6 +111,7 @@ const (
 	Output
 	Clock
 	Pwm
+	Spi
 )
 
 // State of pin, High / Low
@@ -137,9 +141,11 @@ var (
 	gpioMem  []uint32
 	clkMem   []uint32
 	pwmMem   []uint32
+	spiMem   []uint32
 	gpioMem8 []uint8
 	clkMem8  []uint8
 	pwmMem8  []uint8
+	spiMem8  []uint8
 )
 
 // Set pin as Input
@@ -243,14 +249,17 @@ func PinMode(pin Pin, mode Mode) {
 	shift := (uint8(pin) % 10) * 3
 	f := uint32(0)
 
+	const in = 0   // 000
+	const out = 1  // 001
 	const alt0 = 4 // 100
+	const alt4 = 3 // 011
 	const alt5 = 2 // 010
 
 	switch mode {
 	case Input:
-		f = 0 // 000
+		f = in
 	case Output:
-		f = 1 // 001
+		f = out
 	case Clock:
 		switch pin {
 		case 4, 5, 6, 32, 34, 42, 43, 44:
@@ -269,6 +278,19 @@ func PinMode(pin Pin, mode Mode) {
 		default:
 			return
 		}
+	case Spi:
+		switch pin {
+		case 7, 8, 9, 10, 11: // SPI0
+			f = alt0
+		case 35, 36, 37, 38, 39: // SPI0
+			f = alt0
+		case 16, 17, 18, 19, 20, 21: // SPI1
+			f = alt4
+		case 40, 41, 42, 43, 44, 45: // SPI2
+			f = alt4
+		default:
+			return
+		}
 	}
 
 	memlock.Lock()
@@ -284,19 +306,19 @@ func PinMode(pin Pin, mode Mode) {
 func WritePin(pin Pin, state State) {
 	p := uint8(pin)
 
-	// Clear register, 10 / 11 depending on bank
 	// Set register, 7 / 8 depending on bank
-	clearReg := p/32 + 10
+	// Clear register, 10 / 11 depending on bank
 	setReg := p/32 + 7
+	clearReg := p/32 + 10
 
 	memlock.Lock()
-	defer memlock.Unlock()
 
 	if state == Low {
 		gpioMem[clearReg] = 1 << (p & 31)
 	} else {
 		gpioMem[setReg] = 1 << (p & 31)
 	}
+	memlock.Unlock() // not deferring saves ~600ns
 }
 
 // Read the state of a pin
@@ -312,14 +334,23 @@ func ReadPin(pin Pin) State {
 }
 
 // Toggle a pin state (high -> low -> high)
-// TODO: probably possible to do this much faster without read
 func TogglePin(pin Pin) {
-	switch ReadPin(pin) {
+	p := uint8(pin)
-	case Low:
+
-		pin.High()
+	setReg := p/32 + 7
-	case High:
+	clearReg := p/32 + 10
-		pin.Low()
+	levelReg := p/32 + 13
+
+	bit := uint32(1 << (p & 31))
+
+	memlock.Lock()
+
+	if (gpioMem[levelReg] & bit) != 0 {
+		gpioMem[clearReg] = bit
+	} else {
+		gpioMem[setReg] = bit
 	}
+	memlock.Unlock()
 }
 
 // Enable edge event detection on pin.
@@ -346,14 +377,14 @@ func DetectEdge(pin Pin, edge Edge) {
 	bit := uint32(1 << (p & 31))
 
 	if edge&RiseEdge > 0 { // set bit
-		gpioMem[renReg] = gpioMem[renReg] | bit
+		gpioMem[renReg] |= bit
 	} else { // clear bit
-		gpioMem[renReg] = gpioMem[renReg] &^ bit
+		gpioMem[renReg] &^= bit
 	}
 	if edge&FallEdge > 0 { // set bit
-		gpioMem[fenReg] = gpioMem[fenReg] | bit
+		gpioMem[fenReg] |= bit
 	} else { // clear bit
-		gpioMem[fenReg] = gpioMem[fenReg] &^ bit
+		gpioMem[fenReg] &^= bit
 	}
 
 	gpioMem[edsReg] = bit // to clear outdated detection
@@ -387,9 +418,9 @@ func PullMode(pin Pin, pull Pull) {
 
 	switch pull {
 	case PullDown, PullUp:
-		gpioMem[pullReg] = gpioMem[pullReg]&^3 | uint32(pull)
+		gpioMem[pullReg] |= uint32(pull)
 	case PullOff:
-		gpioMem[pullReg] = gpioMem[pullReg] &^ 3
+		gpioMem[pullReg] &^= 3
 	}
 
 	// Wait for value to clock in, this is ugly, sorry :(
@@ -400,7 +431,7 @@ func PullMode(pin Pin, pull Pull) {
 	// Wait for value to clock in
 	time.Sleep(time.Microsecond)
 
-	gpioMem[pullReg] = gpioMem[pullReg] &^ 3
+	gpioMem[pullReg] &^= 3
 	gpioMem[pullClkReg] = 0
 
 }
@@ -537,14 +568,14 @@ func SetDutyCycle(pin Pin, dutyLen, cycleLen uint32) {
 func StopPwm() {
 	const pwmCtlReg = 0
 	const pwen = 1
-	pwmMem[pwmCtlReg] = pwmMem[pwmCtlReg] &^ (pwen<<8 | pwen)
+	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
+	pwmMem[pwmCtlReg] |= pwen<<8 | pwen
 }
 
 // Open and memory map GPIO memory range from /dev/mem .
@@ -584,6 +615,12 @@ func Open() (err error) {
 		return
 	}
 
+	// Memory map spi registers to slice
+	spiMem, spiMem8, err = memMap(file.Fd(), spiBase)
+	if err != nil {
+		return
+	}
+
 	return nil
 }
 
@@ -619,6 +656,9 @@ func Close() error {
 	if err := syscall.Munmap(pwmMem8); err != nil {
 		return err
 	}
+	if err := syscall.Munmap(spiMem8); err != nil {
+		return err
+	}
 	return nil
 }
 

spi.go

@@ -0,0 +1,134 @@
+package rpio
+
+import (
+	"errors"
+)
+
+var (
+	SpiMapError = errors.New("SPI registers not mapped correctly - are you root?")
+)
+
+const (
+	SPI0 = iota // only spi0 supported for now
+	SPI1        // aux
+	SPI2        // aux
+)
+
+const (
+	csReg     = 0
+	fifoReg   = 1 // TX/RX FIFO
+	clkDivReg = 2
+)
+
+// Sets SPI pins of given device to SIP mode
+// (CE0, CE1, [CE2], SCLK, MOSI, MISO)
+// also reset SPI control register
+func SpiBegin(dev int) error {
+	spiMem[csReg] = 0 // reset spi settings to default
+	if spiMem[csReg] == 0 {
+		// this should not read only zeroes after reset -> mem map failed
+		return SpiMapError
+	}
+
+	for _, pin := range getSpiPins(dev) {
+		pin.Mode(Spi)
+	}
+
+	clearSpiTxRxFifo()
+	setSpiDiv(128)
+	return nil
+}
+
+// Sets SPI pins of given device to default (Input) mode
+func SpiEnd(dev int) {
+	var pins = getSpiPins(dev)
+	for _, pin := range pins {
+		pin.Mode(Input)
+	}
+}
+
+// Set (maximal) speed [Hz] of SPI clock
+// Param speed may be as big as 125MHz in theory, but
+// only values up to 31.25MHz are considered relayable.
+func SpiSpeed(speed int) {
+	const baseFreq = 250 * 1000000
+	cdiv := uint32(baseFreq / speed)
+	setSpiDiv(cdiv)
+}
+
+// Select chip, one of 0, 1, 2
+// for selecting slave on CE0, CE1, or CE2
+func SpiChipSelect(chip int) { // control & status
+	const csMask = 3 // chip select has 2 bits
+
+	cs := uint32(chip & csMask)
+
+	spiMem[csReg] = spiMem[csReg]&^csMask | cs
+}
+
+// Transmit all bytes in data to slave
+// and simultaneously receives bytes from slave to data
+func SpiTransfer(data []byte) { // control & status
+	const ta = 1 << 7   // transfer active
+	const txd = 1 << 18 // tx fifo can accept data
+	const rxd = 1 << 17 // rx fifo contains data
+	const done = 1 << 16
+
+	length := len(data)
+	i := 0 // data index
+
+	clearSpiTxRxFifo()
+
+	// set TA = 1
+	spiMem[csReg] |= ta
+
+	for i < length {
+		// Poll TXD writing bytes to SPI_FIFO
+		for spiMem[csReg]&txd == 0 {
+		}
+		spiMem[fifoReg] = uint32(data[i])
+		// Poll RXD reading bytes from SPI_FIFO
+		for spiMem[csReg]&rxd == 0 {
+		}
+		data[i] = byte(spiMem[fifoReg])
+		i++
+	}
+
+	// wait for DONE
+	for spiMem[csReg]&done == 0 {
+	}
+
+	// Set TA = 0
+	spiMem[csReg] &^= ta
+}
+
+func setSpiDiv(div uint32) {
+	const divMask = 1<<16 - 1 - 1 // cdiv have 16 bits and must be odd (for some reason)
+	spiMem[clkDivReg] = div & divMask
+}
+
+func clearSpiTxRxFifo() {
+	const clearTxRx = 1<<5 | 1<<4
+
+	spiMem[csReg] |= clearTxRx
+}
+
+func getSpiPins(dev int) []Pin {
+	switch dev {
+	case SPI0:
+		return []Pin{
+			7, 8, 9, 10, 11,
+			// 35, 36, 37, 38, 39, // only one set of SPI0 can be set in Spi mode at a time
+		}
+	case SPI1:
+		return []Pin{
+			16, 17, 18, 19, 20, 21,
+		}
+	case SPI2:
+		return []Pin{
+			40, 41, 42, 43, 44, 45,
+		}
+	default:
+		return []Pin{}
+	}
+}