Go - Joystick Bricklet 2.0

This is the description of the Go API bindings for the Joystick Bricklet 2.0. General information and technical specifications for the Joystick Bricklet 2.0 are summarized in its hardware description.

An installation guide for the Go API bindings is part of their general description. Additional documentation can be found on godoc.org.

Examples

The example code below is Public Domain (CC0 1.0).

Simple

Download (example_simple.go)

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package main

import (
    "fmt"
    "github.com/Tinkerforge/go-api-bindings/ipconnection"
    "github.com/Tinkerforge/go-api-bindings/joystick_v2_bricklet"
)

const ADDR string = "localhost:4223"
const UID string = "XYZ" // Change XYZ to the UID of your Joystick Bricklet 2.0.

func main() {
    ipcon := ipconnection.New()
    defer ipcon.Close()
    j, _ := joystick_v2_bricklet.New(UID, &ipcon) // Create device object.

    ipcon.Connect(ADDR) // Connect to brickd.
    defer ipcon.Disconnect()
    // Don't use device before ipcon is connected.

    // Get current position.
    x, y, _ := j.GetPosition()

    fmt.Printf("Position [X]: \n", x)
    fmt.Printf("Position [Y]: \n", y)

    fmt.Print("Press enter to exit.")
    fmt.Scanln()
}

Callback

Download (example_callback.go)

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package main

import (
    "fmt"
    "github.com/Tinkerforge/go-api-bindings/ipconnection"
    "github.com/Tinkerforge/go-api-bindings/joystick_v2_bricklet"
)

const ADDR string = "localhost:4223"
const UID string = "XYZ" // Change XYZ to the UID of your Joystick Bricklet 2.0.

func main() {
    ipcon := ipconnection.New()
    defer ipcon.Close()
    j, _ := joystick_v2_bricklet.New(UID, &ipcon) // Create device object.

    ipcon.Connect(ADDR) // Connect to brickd.
    defer ipcon.Disconnect()
    // Don't use device before ipcon is connected.

    j.RegisterPressedCallback(func(pressed bool) {
        fmt.Printf("Pressed: %s\n", pressed)
    })

    // Set period for pressed callback to 0.01s (10ms).
    j.SetPressedCallbackConfiguration(10, true)

    fmt.Print("Press enter to exit.")
    fmt.Scanln()
}

API

The Joystick Bricklet 2.0 API is defined in the package github.com/Tinkerforge/go-api-bindings/joystick_v2_bricklet

Nearly every function of the Go bindings can return an DeviceError, implementing the error interface. The error can have one of the following values:

  • DeviceErrorSuccess = 0
  • DeviceErrorInvalidParameter = 1
  • DeviceErrorFunctionNotSupported = 2
  • DeviceErrorUnknownError = 3

which correspond to the values returned from Bricks and Bricklets.

All functions listed below are thread-safe.

Basic Functions

func NewJoystickV2Bricklet(uid string, ipcon *IPConnection) (device JoystickV2Bricklet, err error)

Creates a new JoystickV2Bricklet object with the unique device ID uid and adds it to the IPConnection ipcon:

This device object can be used after the IPConnection has been connected (see examples above).

func (*JoystickV2Bricklet) GetPosition() (x int16, y int16, err error)

Returns the position of the joystick. The value ranges between -100 and 100 for both axis. The middle position of the joystick is x=0, y=0. The returned values are averaged and calibrated (see Calibrate()).

If you want to get the position periodically, it is recommended to use the RegisterPositionCallback callback and set the period with SetPositionCallbackConfiguration().

func (*JoystickV2Bricklet) IsPressed() (pressed bool, err error)

Returns true if the button is pressed and false otherwise.

If you want to get the press-state periodically, it is recommended to use the RegisterPressedCallback callback and set the period with SetPressedCallbackConfiguration().

Advanced Functions

func (*JoystickV2Bricklet) Calibrate() (err error)

Calibrates the middle position of the joystick. If your Joystick Bricklet 2.0 does not return x=0 and y=0 in the middle position, call this function while the joystick is standing still in the middle position.

The resulting calibration will be saved in non-volatile memory, thus you only have to calibrate it once.

func (*JoystickV2Bricklet) GetAPIVersion() (apiVersion [3]uint8, err error)

Returns the version of the API definition (major, minor, revision) implemented by this API bindings. This is neither the release version of this API bindings nor does it tell you anything about the represented Brick or Bricklet.

func (*JoystickV2Bricklet) GetResponseExpected(functionId uint8) (responseExpected bool, err error)

Returns the response expected flag for the function specified by the function ID parameter. It is true if the function is expected to send a response, false otherwise.

For getter functions this is enabled by default and cannot be disabled, because those functions will always send a response. For callback configuration functions it is enabled by default too, but can be disabled by SetResponseExpected(). For setter functions it is disabled by default and can be enabled.

Enabling the response expected flag for a setter function allows to detect timeouts and other error conditions calls of this setter as well. The device will then send a response for this purpose. If this flag is disabled for a setter function then no response is send and errors are silently ignored, because they cannot be detected.

See SetResponseExpected() for the list of function ID constants available for this function.

func (*JoystickV2Bricklet) SetResponseExpected(functionId uint8, responseExpected bool) (err error)

Changes the response expected flag of the function specified by the function ID parameter. This flag can only be changed for setter (default value: false) and callback configuration functions (default value: true). For getter functions it is always enabled.

Enabling the response expected flag for a setter function allows to detect timeouts and other error conditions calls of this setter as well. The device will then send a response for this purpose. If this flag is disabled for a setter function then no response is send and errors are silently ignored, because they cannot be detected.

The following function ID constants are available for this function:

  • FunctionCalibrate = 3
  • FunctionSetPositionCallbackConfiguration = 4
  • FunctionSetPressedCallbackConfiguration = 7
  • FunctionSetWriteFirmwarePointer = 237
  • FunctionSetStatusLEDConfig = 239
  • FunctionReset = 243
  • FunctionWriteUID = 248
func (*JoystickV2Bricklet) SetResponseExpectedAll(responseExpected bool) (err error)

Changes the response expected flag for all setter and callback configuration functions of this device at once.

func (*JoystickV2Bricklet) GetSPITFPErrorCount() (errorCountAckChecksum uint32, errorCountMessageChecksum uint32, errorCountFrame uint32, errorCountOverflow uint32, err error)

Returns the error count for the communication between Brick and Bricklet.

The errors are divided into

  • ACK checksum errors,
  • message checksum errors,
  • framing errors and
  • overflow errors.

The errors counts are for errors that occur on the Bricklet side. All Bricks have a similar function that returns the errors on the Brick side.

func (*JoystickV2Bricklet) SetBootloaderMode(mode BootloaderMode) (status BootloaderStatus, err error)

Sets the bootloader mode and returns the status after the requested mode change was instigated.

You can change from bootloader mode to firmware mode and vice versa. A change from bootloader mode to firmware mode will only take place if the entry function, device identifier and CRC are present and correct.

This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.

The following constants are available for this function:

  • BootloaderModeBootloader = 0
  • BootloaderModeFirmware = 1
  • BootloaderModeBootloaderWaitForReboot = 2
  • BootloaderModeFirmwareWaitForReboot = 3
  • BootloaderModeFirmwareWaitForEraseAndReboot = 4
  • BootloaderStatusOK = 0
  • BootloaderStatusInvalidMode = 1
  • BootloaderStatusNoChange = 2
  • BootloaderStatusEntryFunctionNotPresent = 3
  • BootloaderStatusDeviceIdentifierIncorrect = 4
  • BootloaderStatusCRCMismatch = 5
func (*JoystickV2Bricklet) GetBootloaderMode() (mode BootloaderMode, err error)

Returns the current bootloader mode, see SetBootloaderMode().

The following constants are available for this function:

  • BootloaderModeBootloader = 0
  • BootloaderModeFirmware = 1
  • BootloaderModeBootloaderWaitForReboot = 2
  • BootloaderModeFirmwareWaitForReboot = 3
  • BootloaderModeFirmwareWaitForEraseAndReboot = 4
func (*JoystickV2Bricklet) SetWriteFirmwarePointer(pointer uint32) (err error)

Sets the firmware pointer for WriteFirmware(). The pointer has to be increased by chunks of size 64. The data is written to flash every 4 chunks (which equals to one page of size 256).

This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.

func (*JoystickV2Bricklet) WriteFirmware(data [64]uint8) (status uint8, err error)

Writes 64 Bytes of firmware at the position as written by SetWriteFirmwarePointer() before. The firmware is written to flash every 4 chunks.

You can only write firmware in bootloader mode.

This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.

func (*JoystickV2Bricklet) SetStatusLEDConfig(config StatusLEDConfig) (err error)

Sets the status LED configuration. By default the LED shows communication traffic between Brick and Bricklet, it flickers once for every 10 received data packets.

You can also turn the LED permanently on/off or show a heartbeat.

If the Bricklet is in bootloader mode, the LED is will show heartbeat by default.

The following constants are available for this function:

  • StatusLEDConfigOff = 0
  • StatusLEDConfigOn = 1
  • StatusLEDConfigShowHeartbeat = 2
  • StatusLEDConfigShowStatus = 3
func (*JoystickV2Bricklet) GetStatusLEDConfig() (config StatusLEDConfig, err error)

Returns the configuration as set by SetStatusLEDConfig()

The following constants are available for this function:

  • StatusLEDConfigOff = 0
  • StatusLEDConfigOn = 1
  • StatusLEDConfigShowHeartbeat = 2
  • StatusLEDConfigShowStatus = 3
func (*JoystickV2Bricklet) GetChipTemperature() (temperature int16, err error)

Returns the temperature in °C as measured inside the microcontroller. The value returned is not the ambient temperature!

The temperature is only proportional to the real temperature and it has bad accuracy. Practically it is only useful as an indicator for temperature changes.

func (*JoystickV2Bricklet) Reset() (err error)

Calling this function will reset the Bricklet. All configurations will be lost.

After a reset you have to create new device objects, calling functions on the existing ones will result in undefined behavior!

func (*JoystickV2Bricklet) WriteUID(uid uint32) (err error)

Writes a new UID into flash. If you want to set a new UID you have to decode the Base58 encoded UID string into an integer first.

We recommend that you use Brick Viewer to change the UID.

func (*JoystickV2Bricklet) ReadUID() (uid uint32, err error)

Returns the current UID as an integer. Encode as Base58 to get the usual string version.

func (*JoystickV2Bricklet) GetIdentity() (uid string, connectedUid string, position rune, hardwareVersion [3]uint8, firmwareVersion [3]uint8, deviceIdentifier uint16, err error)

Returns the UID, the UID where the Bricklet is connected to, the position, the hardware and firmware version as well as the device identifier.

The position can be 'a', 'b', 'c' or 'd'.

The device identifier numbers can be found here. There is also a constant for the device identifier of this Bricklet.

Callback Configuration Functions

func (*JoystickV2Bricklet) SetPositionCallbackConfiguration(period uint32, valueHasToChange bool) (err error)

The period in ms is the period with which the RegisterPositionCallback callback is triggered periodically. A value of 0 turns the callback off.

If the value has to change-parameter is set to true, the callback is only triggered after at least one of the values has changed. If the values didn't change within the period, the callback is triggered immediately on change.

If it is set to false, the callback is continuously triggered with the period, independent of the value.

The default value is (0, false).

func (*JoystickV2Bricklet) GetPositionCallbackConfiguration() (period uint32, valueHasToChange bool, err error)

Returns the callback configuration as set by SetPositionCallbackConfiguration().

func (*JoystickV2Bricklet) SetPressedCallbackConfiguration(period uint32, valueHasToChange bool) (err error)

The period in ms is the period with which the RegisterPressedCallback callback is triggered periodically. A value of 0 turns the callback off.

If the value has to change-parameter is set to true, the callback is only triggered after at least one of the values has changed. If the values didn't change within the period, the callback is triggered immediately on change.

If it is set to false, the callback is continuously triggered with the period, independent of the value.

The default value is (0, false).

func (*JoystickV2Bricklet) GetPressedCallbackConfiguration() (period uint32, valueHasToChange bool, err error)

Returns the callback configuration as set by SetPressedCallbackConfiguration().

Callbacks

Callbacks can be registered to receive time critical or recurring data from the device. The registration is done with the corresponding Register*Callback function, which returns a unique callback ID. This ID can be used to deregister the callback later.

Note

Using callbacks for recurring events is always preferred compared to using getters. It will use less USB bandwidth and the latency will be a lot better, since there is no round trip time.

func (*JoystickV2Bricklet) RegisterPositionCallback(func(x int16, y int16)) (registrationId uint64)

A callback can be registered for this event with the RegisterPositionCallback() function. This function returns the ID of the registered callback. An added callback can be removed with the DeregisterPositionCallback(registrationId uint64) function.

This callback is triggered periodically according to the configuration set by SetPositionCallbackConfiguration().

The callback parameters are the same as with GetPosition().

func (*JoystickV2Bricklet) RegisterPressedCallback(func(pressed bool)) (registrationId uint64)

A callback can be registered for this event with the RegisterPressedCallback() function. This function returns the ID of the registered callback. An added callback can be removed with the DeregisterPressedCallback(registrationId uint64) function.

This callback is triggered periodically according to the configuration set by SetPressedCallbackConfiguration().

The callback parameters are the same as with IsPressed().

Constants

joystick_v2_bricklet.DeviceIdentifier

This constant is used to identify a Joystick Bricklet 2.0.

The GetIdentity() function and the (*IPConnection) RegisterEnumerateCallback callback of the IPConnection have a deviceIdentifier parameter to specify the Brick's or Bricklet's type.

joystick_v2_bricklet.DeviceDisplayName

This constant represents the human readable name of a Joystick Bricklet 2.0.