This is the description of the Shell 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 Shell API bindings is part of their general description.
The example code below is Public Domain (CC0 1.0).
Download (example-callback.sh)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 | #!/bin/sh
# connects to localhost:4223 by default, use --host and --port to change it
# change to your UID
uid=XYZ
# enable position reached callback
tinkerforge call servo-brick $uid enable-position-reached-callback
# set velocity to 100°/s. This has to be smaller or equal to
# maximum velocity of the servo, otherwise cb_reached will be
# called to early.
tinkerforge call servo-brick $uid set-velocity 0 10000
tinkerforge call servo-brick $uid set-position 0 9000
tinkerforge call servo-brick $uid enable 0
# use position reached callback to swing back and forth
tinkerforge dispatch servo-brick $uid position-reached\
--execute "if [ {position} -eq 9000 ];
then echo 'Position: 90°, going to -90°' && tinkerforge call servo-brick $uid set-position 0 -9000;
elif [ {position} -eq -9000 ];
then echo 'Position: -90°, going to 90°' && tinkerforge call servo-brick $uid set-position 0 9000;
else echo error; fi"
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Download (example-configuration.sh)
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 | #!/bin/sh
# connects to localhost:4223 by default, use --host and --port to change it
# change to your UID
uid=XYZ
# 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°
tinkerforge call servo-brick $uid set-output-voltage 5500
tinkerforge call servo-brick $uid set-degree 0 -10000 10000
tinkerforge call servo-brick $uid set-pulse-width 0 1000 2000
tinkerforge call servo-brick $uid set-period 0 19500
tinkerforge call servo-brick $uid set-acceleration 0 1000 # slow acceleration
tinkerforge call servo-brick $uid set-velocity 0 65535 # full speed
tinkerforge call servo-brick $uid set-degree 5 -9000 9000
tinkerforge call servo-brick $uid set-pulse-width 5 950 1950
tinkerforge call servo-brick $uid set-period 5 20000
tinkerforge call servo-brick $uid set-acceleration 5 65535 # full acceleration
tinkerforge call servo-brick $uid set-velocity 5 65535 # full speed
tinkerforge call servo-brick $uid set-position 0 10000 # set to most right position
tinkerforge call servo-brick $uid enable 0
tinkerforge call servo-brick $uid set-position 5 -9000 # set to most left position
tinkerforge call servo-brick $uid enable 5
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Possible exit codes for all tinkerforge commands are:
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.
The common options of the call and dispatch commands are documented here. The specific command structure is shown below.
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The call command is used to call a function of the Servo Brick. It can take several options:
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The dispatch command is used to dispatch a callback of the Servo Brick. It can take several options:
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The <function> to be called can take different options depending of its kind. All functions can take the following options:
Getter functions can take the following options:
Setter functions can take the following options:
The --expect-response option for setter functions allows to detect timeouts and other error conditions calls of setters as well. The device will then send a response for this purpose. If this option is not given for a setter function then no response is send and errors are silently ignored, because they cannot be detected.
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The <callback> to be dispatched can take several options:
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Output: | no output |
Enables a servo (0 to 6). If a servo is enabled, the configured position, velocity, acceleration, etc. are applied immediately.
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Output: | no output |
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.
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Returns true if the specified servo is enabled, false otherwise.
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Output: | no output |
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 set-degree.
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 set-degree.
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Returns the position of the specified servo as set by set-position.
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Returns the current position of the specified servo. This may not be the value of set-position if the servo is currently approaching a position goal.
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Output: | no output |
Sets the maximum velocity of the specified servo in °/100s. The velocity is accelerated according to the value set by set-acceleration.
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.
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Returns the velocity of the specified servo as set by set-velocity.
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Returns the current velocity of the specified servo. This may not be the value of set-velocity if the servo is currently approaching a velocity goal.
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Output: | no output |
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.
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Returns the acceleration for the specified servo as set by set-acceleration.
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Output: | no output |
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.
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Returns the output voltage as specified by set-output-voltage.
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Output: | no output |
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.
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Returns the minimum and maximum pulse width for the specified servo as set by set-pulse-width.
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Output: | no output |
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 set-position 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.
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Returns the minimum and maximum degree for the specified servo as set by set-degree.
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Output: | no output |
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).
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Returns the period for the specified servo as set by set-period.
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Returns the current consumption of the specified servo in mA.
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Returns the current consumption of all servos together in mA.
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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.
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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
Output: | no output |
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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).
Output: | no output |
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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).
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Returns true if the status LED is enabled, false otherwise.
New in version 2.3.1 (Firmware).
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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.
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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.
Output: | no output |
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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!
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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.
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Output: | no output |
Sets the minimum voltage in mV, below which the under-voltage 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).
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Returns the minimum voltage as set by set-minimum-voltage
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Enables the position-reached callback.
Default is disabled.
New in version 2.0.1 (Firmware).
Output: | no output |
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Disables the position-reached callback.
Default is disabled.
New in version 2.0.1 (Firmware).
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Returns true if position-reached callback is enabled, false otherwise.
New in version 2.0.1 (Firmware).
Output: | no output |
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Enables the velocity-reached callback.
Default is disabled.
New in version 2.0.1 (Firmware).
Output: | no output |
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Disables the velocity-reached callback.
Default is disabled.
New in version 2.0.1 (Firmware).
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Returns true if velocity-reached callback is enabled, false otherwise.
New in version 2.0.1 (Firmware).
Callbacks can be used to receive time critical or recurring data from the device:
tinkerforge dispatch servo-brick <uid> example
The available callbacks 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.
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This callback is triggered when the input voltage drops below the value set by set-minimum-voltage. The parameter is the current voltage given in mV.
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This callback is triggered when a position set by set-position is reached. The parameters are the servo and the position that is reached.
You can enable this callback with enable-position-reached-callback.
Note
Since we can't get any feedback from the servo, this only works if the velocity (see set-velocity) 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.
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This callback is triggered when a velocity set by set-velocity is reached. The parameters are the servo and the velocity that is reached.
You can enable this callback with enable-velocity-reached-callback.
Note
Since we can't get any feedback from the servo, this only works if the acceleration (see set-acceleration) 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.