Adding Support for MCP3208 (12 bit version of MCP3008)

convertors/mcp3008/mcp3008.go

@@ -8,11 +8,16 @@ import (
 
 // MCP3008 represents a mcp3008 8bit DAC.
 type MCP3008 struct {
-	Mode byte
-
-	Bus embd.SPIBus
+	Mode, Bits byte
+	Bus        embd.SPIBus
 }
 
+//How many bits does the
+const (
+	Bits10 = iota //10 bit MCP300** family
+	Bits12        //12 bit MCP320** family
+)
+
 const (
 	// SingleMode represents the single-ended mode for the mcp3008.
 	SingleMode = 1
@@ -22,8 +27,8 @@ const (
 )
 
 // New creates a representation of the mcp3008 convertor
-func New(mode byte, bus embd.SPIBus) *MCP3008 {
-	return &MCP3008{mode, bus}
+func New(mode, bits byte, bus embd.SPIBus) *MCP3008 {
+	return &MCP3008{Mode: mode, Bus: bus}
 }
 
 const (
@@ -33,14 +38,28 @@ const (
 // AnalogValueAt returns the analog value at the given channel of the convertor.
 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
+	switch m.Bits {
+	case Bits10:
+		data[0] = startBit
+		data[1] = uint8(m.Mode)<<7 | uint8(chanNum)<<4
+		data[2] = 0
+	case Bits12:
+		data[0] = (uint8(startBit) << 2) + (uint8(m.Mode) << 1) + (uint8(chanNum) >> 2)
+		data[1] = uint8(chanNum) << 6
+		data[2] = 0
+	}
 
 	glog.V(2).Infof("mcp3008: sendingdata buffer %v", data)
 	if err := m.Bus.TransferAndReceiveData(data[:]); err != nil {
 		return 0, err
 	}
+	switch m.Bits {
+	case Bits10:
+		return int(uint16(data[1]&0x03)<<8 | uint16(data[2])), nil
+	case Bits12:
+		return int(uint16(data[1]&0x0f)<<8 | uint16(data[2])), nil
+	default:
+		panic("mcp3008: unknown number of bits")
+	}
 
-	return int(uint16(data[1]&0x03)<<8 | uint16(data[2])), nil
 }

samples/mcp3008.go

@@ -32,7 +32,7 @@ func main() {
 	spiBus := embd.NewSPIBus(embd.SPIMode0, channel, speed, bpw, delay)
 	defer spiBus.Close()
 
-	adc := mcp3008.New(mcp3008.SingleMode, spiBus)
+	adc := mcp3008.New(mcp3008.SingleMode, mcp3008.Bits10, spiBus)
 
 	for i := 0; i < 20; i++ {
 		time.Sleep(1 * time.Second)

samples/mcp3208.go

@@ -0,0 +1,47 @@
+// +build ignore
+
+// this sample uses the mcp3008 package to interface with a similar MCP3208, which is a 12 bit variant. Works without code change on bbb and rpi
+package main
+
+import (
+	"flag"
+	"fmt"
+	"time"
+
+	"github.com/kidoman/embd"
+	  "github.com/kidoman/embd/convertors/mcp3008"
+	_ "github.com/kidoman/embd/host/all"
+)
+
+const (
+	channel = 0
+	speed   = 1000000
+	bpw     = 8
+	delay   = 0
+)
+
+func main() {
+	flag.Parse()
+	fmt.Println("this is a sample code for mcp3008 10bit 8 channel ADC")
+
+	if err := embd.InitSPI(); err != nil {
+		panic(err)
+	}
+	defer embd.CloseSPI()
+
+	spiBus := embd.NewSPIBus(embd.SPIMode0, channel, speed, bpw, delay)
+	defer spiBus.Close()
+
+	adc := &mcp3008.MCP3008{Mode: mcp3008.SingleMode, Bus: spiBus, Bits: mcp3008.Bits12}
+
+	// adc := mcp3008.New(mcp3008.SingleMode, spiBus)
+
+	for i := 0; i < 20; i++ {
+		time.Sleep(1 * time.Second)
+		val, err := adc.AnalogValueAt(0)
+		if err != nil {
+			fmt.Println("Error: ", err)
+		}
+		fmt.Printf("analog value is: %v\n", val)
+	}
+}