ev3dev.1.0.0-compatible motor api

Motor/motors.go

@@ -2,10 +2,10 @@
 package Motor
 
 import (
-	"fmt"
 	"github.com/mattrajca/GoEV3/utilities"
 	"log"
 	"os"
+	"path"
 )
 
 // Constants for output ports.
@@ -18,58 +18,108 @@ const (
 	OutPortD         = "D"
 )
 
-func findFilename(port OutPort) string {
-	filename := fmt.Sprintf("/sys/class/tacho-motor/out%s:motor:tacho", string(port))
+// Names of files which constitute the low-level motor API
+const (
+	rootMotorPath = "/sys/class/tacho-motor"
+	// File descriptors for getting/setting parameters
+	portFD           = "port_name"
+	regulationModeFD = "regulation_mode"
+	speedGetterFD    = "pulses_per_second"
+	speedSetterFD    = "pulses_per_second_sp"
+	powerGetterFD    = "duty_cycle"
+	powerSetterFD    = "duty_cycle_sp"
+	runFD            = "run"
+	stopModeFD       = "stop_mode"
+)
+
+func findFolder(port OutPort) string {
+	if _, err := os.Stat(rootMotorPath); os.IsNotExist(err) {
+		log.Fatal("There are no motors connected")
+	}
 
-	if _, err := os.Stat(filename); os.IsNotExist(err) {
-		log.Fatal("Cannot connect to motor %s", port)
+	rootMotorFolder, _ := os.Open(rootMotorPath)
+	motorFolders, _ := rootMotorFolder.Readdir(-1)
+	if len(motorFolders) == 0 {
+		log.Fatal("There are no motors connected")
 	}
 
-	return filename
+	for _, folderInfo := range motorFolders {
+		folder := folderInfo.Name()
+		motorPort := utilities.ReadStringValue(path.Join(rootMotorPath, folder), portFD)
+		if motorPort == "out"+string(port) {
+			return path.Join(rootMotorPath, folder)
+		}
+	}
+
+	log.Fatal("No motor is connected to port %s", port)
+	return ""
 }
 
 // Runs the motor at the given port.
-// `speed` ranges from -100 to 100 and indicates the target speed of the motor, with negative values indicating reverse motion. Depending on the environment, the actual speed of the motor may be lower than the target speed.
+// The meaning of `speed` parameter depends on whether the regulation mode is turned on or off.
+//
+// When the regulation mode is off (by default) `speed` ranges from -100 to 100 and
+// it's absolute value indicates the percent of motor's power usage. It can be roughly interpreted as
+// a motor speed, but deepending on the environment, the actual speed of the motor
+// may be lower than the target speed.
+//
+// When the regulation mode is on (has to be enabled by EnableRegulationMode function) the motor
+// driver attempts to keep the motor speed at the `speed` value you've specified
+// which ranges from -2000 to 2000.
+//
+// Negative values indicate reverse motion regardless of the regulation mode.
 func Run(port OutPort, speed int16) {
-	if speed > 100 || speed < -100 {
-		log.Fatal("The speed must be in range [-100, 100]")
-	}
+	folder := findFolder(port)
+	regulationMode := utilities.ReadStringValue(folder, regulationModeFD)
 
-	utilities.WriteIntValue(findFilename(port), "run", 1)
-	utilities.WriteIntValue(findFilename(port), "speed_setpoint", int64(speed))
+	switch regulationMode {
+	case "on":
+		if speed > 2000 || speed < -2000 {
+			log.Fatal("The speed in regulation mode must be in range [-2000, 2000]")
+		}
+		utilities.WriteIntValue(folder, speedSetterFD, int64(speed))
+		utilities.WriteIntValue(folder, runFD, 1)
+	case "off":
+		if speed > 100 || speed < -100 {
+			log.Fatal("The speed must be in range [-100, 100]")
+		}
+		utilities.WriteIntValue(folder, powerSetterFD, int64(speed))
+		utilities.WriteIntValue(folder, runFD, 1)
+	}
 }
 
 // Stops the motor at the given port.
 func Stop(port OutPort) {
-	utilities.WriteIntValue(findFilename(port), "run", 0)
+	utilities.WriteIntValue(findFolder(port), runFD, 0)
 }
 
 // Reads the operating speed of the motor at the given port.
 func CurrentSpeed(port OutPort) int16 {
-	return utilities.ReadInt16Value(findFilename(port), "speed")
+	return utilities.ReadInt16Value(findFolder(port), speedGetterFD)
 }
 
 // Reads the operating power of the motor at the given port.
 func CurrentPower(port OutPort) int16 {
-	return utilities.ReadInt16Value(findFilename(port), "power")
+	return utilities.ReadInt16Value(findFolder(port), powerGetterFD)
 }
 
-// Enables regulation mode, causing the motor at the given port to compensate for any resistance and maintain its target speed.
+// Enables regulation mode, causing the motor at the given port to compensate
+// for any resistance and maintain its target speed.
 func EnableRegulationMode(port OutPort) {
-	utilities.WriteStringValue(findFilename(port), "regulation_mode", "on")
+	utilities.WriteStringValue(findFolder(port), regulationModeFD, "on")
 }
 
 // Disables regulation mode. Regulation mode is off by default.
 func DisableRegulationMode(port OutPort) {
-	utilities.WriteStringValue(findFilename(port), "regulation_mode", "off")
+	utilities.WriteStringValue(findFolder(port), regulationModeFD, "off")
 }
 
 // Enables brake mode, causing the motor at the given port to brake to stops.
 func EnableBrakeMode(port OutPort) {
-	utilities.WriteStringValue(findFilename(port), "brake_mode", "on")
+	utilities.WriteStringValue(findFolder(port), stopModeFD, "brake")
 }
 
 // Disables brake mode, causing the motor at the given port to coast to stops. Brake mode is off by default.
 func DisableBrakeMode(port OutPort) {
-	utilities.WriteStringValue(findFilename(port), "brake_mode", "off")
+	utilities.WriteStringValue(findFolder(port), stopModeFD, "coast")
 }

utilities/utils.go

@@ -2,11 +2,11 @@
 package utilities
 
 import (
-	"fmt"
 	"io/ioutil"
 	"strconv"
 	"strings"
 	"sync"
+	"path"
 )
 
 var gLocks map[string]*sync.RWMutex
@@ -27,7 +27,7 @@ func ensureLockForFilename(filename string) {
 }
 
 func ReadStringValue(filename string, basename string) string {
-	actualFilename := fmt.Sprintf("%s/%s", filename, basename)
+	actualFilename := path.Join(filename, basename)
 	ensureLockForFilename(actualFilename)
 
 	gLocks[actualFilename].RLock()
@@ -64,7 +64,7 @@ func ReadUInt32Value(filename string, basename string) uint32 {
 }
 
 func WriteStringValue(filename string, basename string, value string) {
-	actualFilename := fmt.Sprintf("%s/%s", filename, basename)
+	actualFilename := path.Join(filename, basename)
 	ensureLockForFilename(actualFilename)
 
 	gLocks[actualFilename].Lock()