This is the description of the MATLAB/Octave API bindings for the Servo Brick. General information and technical specifications for the Servo Brick are summarized in its hardware description.
An installation guide for the MATLAB/Octave API bindings is part of their general description.
The example code below is Public Domain (CC0 1.0).
Download (matlab_example_configuration.m)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 | function matlab_example_configuration()
import com.tinkerforge.IPConnection;
import com.tinkerforge.BrickServo;
HOST = 'localhost';
PORT = 4223;
UID = '5VF5vG'; % Change to your UID
ipcon = IPConnection(); % Create IP connection
servo = BrickServo(UID, ipcon); % Create device object
ipcon.connect(HOST, PORT); % Connect to brickd
% Don't use device before ipcon is connected
% Configure two servos with voltage 5.5V
% Servo 1: Connected to port 0, period of 19.5ms, pulse width of 1 to 2ms
% and operating angle -100 to 100°
%
% Servo 2: Connected to port 5, period of 20ms, pulse width of 0.95
% to 1.95ms and operating angle -90 to 90°
servo.setOutputVoltage(5500);
servo.setDegree(0, -10000, 10000);
servo.setPulseWidth(0, 1000, 2000);
servo.setPeriod(0, 19500);
servo.setAcceleration(0, 1000); % Slow acceleration
servo.setVelocity(0, hex2num('FFFF')); % Full speed
servo.setDegree(5, -9000, 9000);
servo.setPulseWidth(5, 950, 1950);
servo.setPeriod(5, 20000);
servo.setAcceleration(5, hex2num('FFFF')); % Full acceleration
servo.setVelocity(5, hex2num('FFFF')); % Full speed
servo.setPosition(0, 10000); % Set to most right position
servo.enable(0);
servo.setPosition(5, -9000); % Set to most left position
servo.enable(5);
input('Press any key to exit...\n', 's');
ipcon.disconnect();
end
|
Download (matlab_example_callback.m)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 | function matlab_example_callback()
import com.tinkerforge.IPConnection;
import com.tinkerforge.BrickServo;
HOST = 'localhost';
PORT = 4223;
UID = '5VF5vG'; % Change to your UID
ipcon = IPConnection(); % Create IP connection
servo = BrickServo(UID, ipcon); % Create device object
ipcon.connect(HOST, PORT); % Connect to brickd
% Don't use device before ipcon is connected
% Register "position reached callback" to cb_reached
% cb_reached will be called every time a position set with
% set_position is reached
set(servo, 'PositionReachedCallback', @(h, e) cb_reached(e));
servo.enablePositionReachedCallback();
% Set velocity to 100°/s. This has to be smaller or equal to
% maximum velocity of the servo, otherwise cb_reached will be
% called too early
servo.setVelocity(0, 10000);
servo.setPosition(0, 9000);
servo.enable(0);
input('Press any key to exit...\n', 's');
ipcon.disconnect();
end
% Use position reached callback to swing back and forth
function cb_reached(e)
servo = e.getSource();
if e.position == 9000
fprintf('Position: 90°, going to -90°\n');
servo.setPosition(e.servoNum, -9000);
elseif e.position == -9000
fprintf('Position: -90°, going to 90°\n');
servo.setPosition(e.servoNum, 9000);
else
fprintf('Error\n'); % Can only happen if another program sets position
end
end
|
Download (octave_example_configuration.m)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 | function octave_example_configuration()
more off;
HOST = "localhost";
PORT = 4223;
UID = "5VF5vG"; % Change to your UID
ipcon = java_new("com.tinkerforge.IPConnection"); % Create IP connection
servo = java_new("com.tinkerforge.BrickServo", UID, ipcon); % Create device object
ipcon.connect(HOST, PORT); % Connect to brickd
% Don't use device before ipcon is connected
% Configure two servos with voltage 5.5V
% Servo 1: Connected to port 0, period of 19.5ms, pulse width of 1 to 2ms
% and operating angle -100 to 100°
%
% Servo 2: Connected to port 5, period of 20ms, pulse width of 0.95
% to 1.95ms and operating angle -90 to 90°
servo.setOutputVoltage(5500);
servo.setDegree(0, -10000, 10000);
servo.setPulseWidth(0, 1000, 2000);
servo.setPeriod(0, 19500);
servo.setAcceleration(0, 1000); % Slow acceleration
servo.setVelocity(0, hex2num("FFFF")); % Full speed
servo.setDegree(5, -9000, 9000);
servo.setPulseWidth(5, 950, 1950);
servo.setPeriod(5, 20000);
servo.setAcceleration(5, hex2num("FFFF")); % Full acceleration
servo.setVelocity(5, hex2num("FFFF")); % Full speed
servo.setPosition(0, 10000); % Set to most right position
servo.enable(0);
servo.setPosition(5, -9000); % Set to most left position
servo.enable(5);
input("Press any key to exit...\n", "s");
ipcon.disconnect();
end
|
Download (octave_example_callback.m)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 | function octave_example_callback()
more off;
HOST = "localhost";
PORT = 4223;
UID = "5VF5vG"; % Change to your UID
ipcon = java_new("com.tinkerforge.IPConnection"); % Create IP connection
servo = java_new("com.tinkerforge.BrickServo", UID, ipcon); % Create device object
ipcon.connect(HOST, PORT); % Connect to brickd
% Don't use device before ipcon is connected
% Register "position reached callback" to cb_reached
% cb_reached will be called every time a position set with
% set_position is reached
servo.addPositionReachedCallback(@cb_reached);
servo.enablePositionReachedCallback();
% Set velocity to 100°/s. This has to be smaller or equal to
% maximum velocity of the servo, otherwise cb_reached will be
% called too early
servo.setVelocity(0, 10000);
servo.setPosition(0, 9000);
servo.enable(0);
input("Press any key to exit...\n", "s");
ipcon.disconnect();
end
% Use position reached callback to swing back and forth
function cb_reached(e)
servo = e.getSource();
if str2double(e.position.toString()) == 9000
fprintf("Position: 90°, going to -90°\n");
servo.setPosition(e.servoNum, -9000);
elseif str2double(e.position.toString()) == -9000
fprintf("Position: -90°, going to 90°\n");
servo.setPosition(e.servoNum, 9000);
else
fprintf("Error\n"); % Can only happen if another program sets position
end
end
|
Generally, every method of the MATLAB bindings that returns a value can throw a TimeoutException. This exception gets thrown if the device did not respond. If a cable based connection is used, it is unlikely that this exception gets thrown (assuming nobody unplugs the device). However, if a wireless connection is used, timeouts will occur if the distance to the device gets too big.
Beside the TimeoutException there is also a NotConnectedException that is thrown if a method needs to communicate with the device while the IP Connection is not connected.
Since the MATLAB bindings are based on Java and Java does not support multiple return values and return by reference is not possible for primitive types, we use small classes that only consist of member variables. The member variables of the returned objects are described in the corresponding method descriptions.
The package for all Brick/Bricklet bindings and the IP Connection is com.tinkerforge.*
All methods listed below are thread-safe.
Every function of the Servo Brick API that has a servo_num parameter can address a servo with the servo number (0 to 6). If it is a setter function then multiple servos can be addressed at once with a bitmask for the servos, if the highest bit is set. For example: 1 will address servo 1, (1 << 1) | (1 << 5) | (1 << 7) will address servos 1 and 5, 0xFF will address all seven servos, etc. This allows to set configurations to several servos with one function call. It is guaranteed that the changes will take effect in the same PWM period for all servos you specified in the bitmask.
Creates an object with the unique device ID uid.
In MATLAB:
import com.tinkerforge.BrickServo;
servo = BrickServo('YOUR_DEVICE_UID', ipcon);
In Octave:
servo = java_new("com.tinkerforge.BrickServo", "YOUR_DEVICE_UID", ipcon);
This object can then be used after the IP Connection is connected (see examples above).
Enables a servo (0 to 6). If a servo is enabled, the configured position, velocity, acceleration, etc. are applied immediately.
Disables a servo (0 to 6). Disabled servos are not driven at all, i.e. a disabled servo will not hold its position if a load is applied.
Returns true if the specified servo is enabled, false otherwise.
Sets the position in °/100 for the specified servo.
The default range of the position is -9000 to 9000, but it can be specified according to your servo with setDegree().
If you want to control a linear servo or RC brushless motor controller or similar with the Servo Brick, you can also define lengths or speeds with setDegree().
Returns the position of the specified servo as set by setPosition().
Returns the current position of the specified servo. This may not be the value of setPosition() if the servo is currently approaching a position goal.
Sets the maximum velocity of the specified servo in °/100s. The velocity is accelerated according to the value set by setAcceleration().
The minimum velocity is 0 (no movement) and the maximum velocity is 65535. With a value of 65535 the position will be set immediately (no velocity).
The default value is 65535.
Returns the velocity of the specified servo as set by setVelocity().
Returns the current velocity of the specified servo. This may not be the value of setVelocity() if the servo is currently approaching a velocity goal.
Sets the acceleration of the specified servo in °/100s².
The minimum acceleration is 1 and the maximum acceleration is 65535. With a value of 65535 the velocity will be set immediately (no acceleration).
The default value is 65535.
Returns the acceleration for the specified servo as set by setAcceleration().
Sets the output voltages with which the servos are driven in mV. The minimum output voltage is 2000mV and the maximum output voltage is 9000mV.
Note
We recommend that you set this value to the maximum voltage that is specified for your servo, most servos achieve their maximum force only with high voltages.
The default value is 5000.
Returns the output voltage as specified by setOutputVoltage().
Sets the minimum and maximum pulse width of the specified servo in µs.
Usually, servos are controlled with a PWM, whereby the length of the pulse controls the position of the servo. Every servo has different minimum and maximum pulse widths, these can be specified with this function.
If you have a datasheet for your servo that specifies the minimum and maximum pulse width, you should set the values accordingly. If your servo comes without any datasheet you have to find the values via trial and error.
Both values have a range from 1 to 65535 (unsigned 16-bit integer). The minimum must be smaller than the maximum.
The default values are 1000µs (1ms) and 2000µs (2ms) for minimum and maximum pulse width.
Returns the minimum and maximum pulse width for the specified servo as set by setPulseWidth().
The returned object has the public member variables int min and int max.
Sets the minimum and maximum degree for the specified servo (by default given as °/100).
This only specifies the abstract values between which the minimum and maximum pulse width is scaled. For example: If you specify a pulse width of 1000µs to 2000µs and a degree range of -90° to 90°, a call of setPosition() with 0 will result in a pulse width of 1500µs (-90° = 1000µs, 90° = 2000µs, etc.).
Possible usage:
Both values have a possible range from -32767 to 32767 (signed 16-bit integer). The minimum must be smaller than the maximum.
The default values are -9000 and 9000 for the minimum and maximum degree.
Returns the minimum and maximum degree for the specified servo as set by setDegree().
The returned object has the public member variables short min and short max.
Sets the period of the specified servo in µs.
Usually, servos are controlled with a PWM. Different servos expect PWMs with different periods. Most servos run well with a period of about 20ms.
If your servo comes with a datasheet that specifies a period, you should set it accordingly. If you don't have a datasheet and you have no idea what the correct period is, the default value (19.5ms) will most likely work fine.
The minimum possible period is 1µs and the maximum is 65535µs.
The default value is 19.5ms (19500µs).
Returns the period for the specified servo as set by setPeriod().
Returns the current consumption of the specified servo in mA.
Returns the current consumption of all servos together in mA.
Returns the stack input voltage in mV. The stack input voltage is the voltage that is supplied via the stack, i.e. it is given by a Step-Down or Step-Up Power Supply.
Returns the external input voltage in mV. The external input voltage is given via the black power input connector on the Servo Brick.
If there is an external input voltage and a stack input voltage, the motors will be driven by the external input voltage. If there is only a stack voltage present, the motors will be driven by this voltage.
Warning
This means, if you have a high stack voltage and a low external voltage, the motors will be driven with the low external voltage. If you then remove the external connection, it will immediately be driven by the high stack voltage
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.
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.
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 and callbacks it is always disabled.
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:
Changes the response expected flag for all setter and callback configuration functions of this device at once.
Enables the status LED.
The status LED is the blue LED next to the USB connector. If enabled is is on and it flickers if data is transfered. If disabled it is always off.
The default state is enabled.
New in version 2.3.1 (Firmware).
Disables the status LED.
The status LED is the blue LED next to the USB connector. If enabled is is on and it flickers if data is transfered. If disabled it is always off.
The default state is enabled.
New in version 2.3.1 (Firmware).
Returns true if the status LED is enabled, false otherwise.
New in version 2.3.1 (Firmware).
Returns the firmware and protocol version and the name of the Bricklet for a given port.
This functions sole purpose is to allow automatic flashing of v1.x.y Bricklet plugins.
The returned object has the public member variables short protocolVersion, short[] firmwareVersion and String name.
Returns the temperature in °C/10 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 an accuracy of +-15%. Practically it is only useful as an indicator for temperature changes.
Calling this function will reset the Brick. Calling this function on a Brick inside of a stack will reset the whole stack.
After a reset you have to create new device objects, calling functions on the existing ones will result in undefined behavior!
Returns the UID, the UID where the Brick is connected to, the position, the hardware and firmware version as well as the device identifier.
The position can be '0'-'8' (stack position).
The device identifier numbers can be found here. There is also a constant for the device identifier of this Brick.
The returned object has the public member variables String uid, String connectedUid, char position, short[] hardwareVersion, short[] firmwareVersion and int deviceIdentifier.
Sets the minimum voltage in mV, below which the UnderVoltageCallback callback is triggered. The minimum possible value that works with the Servo Brick is 5V. You can use this function to detect the discharge of a battery that is used to drive the stepper motor. If you have a fixed power supply, you likely do not need this functionality.
The default value is 5V (5000mV).
Returns the minimum voltage as set by setMinimumVoltage()
Enables the PositionReachedCallback callback.
Default is disabled.
New in version 2.0.1 (Firmware).
Disables the PositionReachedCallback callback.
Default is disabled.
New in version 2.0.1 (Firmware).
Returns true if PositionReachedCallback callback is enabled, false otherwise.
New in version 2.0.1 (Firmware).
Enables the VelocityReachedCallback callback.
Default is disabled.
New in version 2.0.1 (Firmware).
Disables the VelocityReachedCallback callback.
Default is disabled.
New in version 2.0.1 (Firmware).
Returns true if VelocityReachedCallback callback is enabled, false otherwise.
New in version 2.0.1 (Firmware).
Callbacks can be registered to receive time critical or recurring data from the device. The registration is done with "set" function of MATLAB. The parameters consist of the IP Connection object, the callback name and the callback function. For example, it looks like this in MATLAB:
function cb_example(e)
fprintf('Parameter: %s\n', e.param);
end
set(device, 'ExampleCallback', @(h, e) cb_example(e));
Due to a difference in the Octave Java support the "set" function cannot be used in Octave. The registration is done with "add*Callback" functions of the device object. It looks like this in Octave:
function cb_example(e)
fprintf("Parameter: %s\n", e.param);
end
device.addExampleCallback(@cb_example);
It is possible to add several callbacks and to remove them with the corresponding "remove*Callback" function.
The parameters of the callback are passed to the callback function as fields of the structure e, which is derived from the java.util.EventObject class. The available callback names with corresponding structure fields are described below.
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.
Parameters: | voltage -- int |
---|
This callback is triggered when the input voltage drops below the value set by setMinimumVoltage(). The parameter is the current voltage given in mV.
In MATLAB the set() function can be used to register a callback function to this callback.
In Octave a callback function can be added to this callback using the addUnderVoltageCallback() function. An added callback function can be removed with the removeUnderVoltageCallback() function.
Parameters: |
|
---|
This callback is triggered when a position set by setPosition() is reached. The parameters are the servo and the position that is reached.
You can enable this callback with enablePositionReachedCallback().
Note
Since we can't get any feedback from the servo, this only works if the velocity (see setVelocity()) is set smaller or equal to the maximum velocity of the servo. Otherwise the servo will lag behind the control value and the callback will be triggered too early.
In MATLAB the set() function can be used to register a callback function to this callback.
In Octave a callback function can be added to this callback using the addPositionReachedCallback() function. An added callback function can be removed with the removePositionReachedCallback() function.
Parameters: |
|
---|
This callback is triggered when a velocity set by setVelocity() is reached. The parameters are the servo and the velocity that is reached.
You can enable this callback with enableVelocityReachedCallback().
Note
Since we can't get any feedback from the servo, this only works if the acceleration (see setAcceleration()) is set smaller or equal to the maximum acceleration of the servo. Otherwise the servo will lag behind the control value and the callback will be triggered too early.
In MATLAB the set() function can be used to register a callback function to this callback.
In Octave a callback function can be added to this callback using the addVelocityReachedCallback() function. An added callback function can be removed with the removeVelocityReachedCallback() function.
This constant is used to identify a Servo Brick.
The getIdentity() function and the EnumerateCallback callback of the IP Connection have a deviceIdentifier parameter to specify the Brick's or Bricklet's type.