spi: finishing touches

convertors/mcp3008/mcp3008.go

@@ -3,11 +3,10 @@ package mcp3008
 import (
 	"github.com/golang/glog"
 	"github.com/kidoman/embd"
-
-	_ "github.com/kidoman/embd/host/all"
 )
 
-type mcp3008 struct {
+// MCP3008 represents a mcp3008 8bit DAC
+type MCP3008 struct {
 	mode byte
 
 	bus embd.SPIBus
@@ -16,18 +15,22 @@ type mcp3008 struct {
 var SingleMode byte = 1
 var DifferenceMode byte = 0
 
-func New(mode byte, bus embd.SPIBus) *mcp3008 {
+func New(mode byte, bus embd.SPIBus) *MCP3008 {
-	return &mcp3008{mode, bus}
+	return &MCP3008{mode, bus}
 }
 
-func (m *mcp3008) AnalogValueAt(chanNum int) (int, error) {
+const (
-	data := make([]uint8, 3)
+	startBit = 1
-	data[0] = 1
+)
+
+func (m *MCP3008) AnalogValueAt(chanNum int) (int, error) {
+	var data [3]uint8
+	data[0] = startBit
 	data[1] = uint8(m.mode)<<7 | uint8(chanNum)<<4
 	data[2] = 0
 
 	glog.V(2).Infof("mcp3008: sendingdata buffer %v", data)
-	if err := m.bus.TransferAndRecieveData(data); err != nil {
+	if err := m.bus.TransferAndRecieveData(data[:]); err != nil {
 		return 0, err
 	}
 

host/bbb/bbb.go

@@ -16,7 +16,6 @@ import (
 	"strings"
 
 	"github.com/golang/glog"
-
 	"github.com/kidoman/embd"
 	"github.com/kidoman/embd/host/generic"
 )

host/generic/spibus.go

@@ -129,11 +129,9 @@ func (b *spiBus) setMode() error {
 }
 
 func (b *spiBus) setSpeed() error {
-	var speed uint32
+	speed := defaultSPISpeed
 	if b.speed > 0 {
 		speed = uint32(b.speed)
-	} else {
-		speed = defaultSPISpeed
 	}
 
 	glog.V(3).Infof("spi: setting spi speedMax to %v", speed)
@@ -150,12 +148,9 @@ func (b *spiBus) setSpeed() error {
 }
 
 func (b *spiBus) setBPW() error {
-	var bpw uint8
+	bpw := defaultSPIBPW
-
 	if b.bpw > 0 {
 		bpw = uint8(b.bpw)
-	} else {
-		bpw = defaultSPIBPW
 	}
 
 	glog.V(3).Infof("spi: setting spi bpw to %v", bpw)
@@ -171,13 +166,11 @@ func (b *spiBus) setBPW() error {
 }
 
 func (b *spiBus) setDelay() {
-	var delay uint16
+	delay := defaultDelayms
-
 	if b.delayms > 0 {
 		delay = uint16(b.delayms)
-	} else {
-		delay = defaultDelayms
 	}
+
 	glog.V(3).Infof("spi: delayms set to %v", delay)
 	b.spiTransferData.delayus = delay
 }
@@ -210,11 +203,11 @@ func (b *spiBus) ReceiveData(len int) ([]uint8, error) {
 		return nil, err
 	}
 
-	data := make([]uint8, len)
+	var data [len]uint8
-	if err := b.TransferAndRecieveData(data); err != nil {
+	if err := b.TransferAndRecieveData(data[:]); err != nil {
 		return nil, err
 	}
-	return data, nil
+	return data[:], nil
 }
 
 func (b *spiBus) TransferAndReceiveByte(data byte) (byte, error) {
@@ -222,9 +215,8 @@ func (b *spiBus) TransferAndReceiveByte(data byte) (byte, error) {
 		return 0, err
 	}
 
-	d := make([]uint8, 1)
+	d := [1]uint8{uint8(data)}
-	d[0] = uint8(data)
+	if err := b.TransferAndRecieveData(d[:]); err != nil {
-	if err := b.TransferAndRecieveData(d); err != nil {
 		return 0, err
 	}
 	return d[0], nil
@@ -235,9 +227,8 @@ func (b *spiBus) ReceiveByte() (byte, error) {
 		return 0, err
 	}
 
-	d := make([]uint8, 1)
+	var d [1]uint8
-	err := b.TransferAndRecieveData(d)
+	if err := b.TransferAndRecieveData(d[:]); err != nil {
-	if err != nil {
 		return 0, err
 	}
 	return byte(d[0]), nil

samples/mcp3008.go

@@ -1,5 +1,6 @@
 // +build ignore
 
+// this sample uses the mcp3008 package to interface with the 8-bit ADC and works without code change on bbb and rpi
 package main
 
 import (
@@ -7,9 +8,9 @@ import (
 	"fmt"
 	"time"
 
-	"github.com/kidoman/embd/convertors/mcp3008"
-
 	"github.com/kidoman/embd"
+	"github.com/kidoman/embd/convertors/mcp3008"
+	_ "github.com/kidoman/embd/host/all"
 )
 
 func main() {
@@ -21,7 +22,11 @@ func main() {
 	}
 	defer embd.CloseSPI()
 
-	spiBus := embd.NewSPIBus(embd.SpiMode0, 0, 1000000, 8, 0)
+	channel := 0
+	speed := 1000000
+	bpw := 8
+	delay := 0
+	spiBus := embd.NewSPIBus(embd.SPIMode0, channel, speed, bpw, delay)
 	defer spiBus.Close()
 
 	adc := mcp3008.New(mcp3008.SingleMode, spiBus)

samples/spi.go

@@ -6,7 +6,6 @@ import (
 	"fmt"
 
 	"github.com/kidoman/embd"
-
 	_ "github.com/kidoman/embd/host/all"
 )
 
@@ -16,7 +15,7 @@ func main() {
 	}
 	defer embd.CloseSPI()
 
-	spiBus := embd.NewSPIBus(embd.SpiMode0, 0, 1000000, 8, 0)
+	spiBus := embd.NewSPIBus(embd.SPIMode0, 0, 1000000, 8, 0)
 	defer spiBus.Close()
 
 	dataBuf := []uint8{1, 2, 3}

samples/spimcp3008.go

@@ -18,12 +18,19 @@ func main() {
 	}
 	defer embd.CloseSPI()
 
-	bus := embd.NewSPIBus(embd.SpiMode0, 0, 1000000, 8, 0)
+	channel := 0
+	speed := 1000000
+	bpw := 8
+	delay := 0
+	bus := embd.NewSPIBus(embd.SPIMode0, channel, speed, bpw, delay)
 	defer bus.Close()
 
 	for i := 0; i < 30; i++ {
 		time.Sleep(1 * time.Second)
-		val, _ := getSensorValue(bus)
+		val, err := getSensorValue(bus)
+		if err != nil {
+			panic(err)
+		}
 		fmt.Printf("value is: %v\n", val)
 	}
 }

spi.go

@@ -6,17 +6,17 @@ const (
 	spiCpha = 0x01
 	spiCpol = 0x02
 
-	// SpiMode0 represents the mode0 operation (CPOL=0 CPHA=0) of spi.
+	// SPIMode0 represents the mode0 operation (CPOL=0 CPHA=0) of spi.
-	SpiMode0 = (0 | 0)
+	SPIMode0 = (0 | 0)
 
-	// SpiMode0 represents the mode0 operation (CPOL=0 CPHA=1) of spi.
+	// SPIMode1 represents the mode0 operation (CPOL=0 CPHA=1) of spi.
-	SpiMode1 = (0 | spiCpha)
+	SPIMode1 = (0 | spiCpha)
 
-	// SpiMode0 represents the mode0 operation (CPOL=1 CPHA=0) of spi.
+	// SPIMode2 represents the mode0 operation (CPOL=1 CPHA=0) of spi.
-	SpiMode2 = (spiCpol | 0)
+	SPIMode2 = (spiCpol | 0)
 
-	// SpiMode0 represents the mode0 operation (CPOL=1 CPHA=1) of spi.
+	// SPIMode3 represents the mode0 operation (CPOL=1 CPHA=1) of spi.
-	SpiMode3 = (spiCpol | spiCpha)
+	SPIMode3 = (spiCpol | spiCpha)
 )
 
 // SPI interface allows interaction with the SPI bus.