LibreServo commands (part one)

EDITED: 20/01/2023
FD function added in LibreServo v2.1.

I have spent a lot of time on the command part of LibreServo and I think it is one of the most important parts of the project, it is how LibreServo is presented to the user. It offers a flexibility and possibilities that I have never seen in any manufacturer.

The documentation of the commands I will divide it in two articles, this article is more focused on the description of the commands and the second part is focused on examples and explanation of execution in LibreServo.

The LibreServo commands are as follows:

• Motion commands
  • Linear Motion [M]
  • Trapezoidal Motion [MT]
  • Trapezoidal Motion 50% [Mt]
  • Accelerated trapezoidal Motion [MA]
  • Sine Motion [MS]
  • Sine Motion 50% [Ms]
  • Hermitic Motion [MH]
  • Continuous Motion [MC]
  • Continuous Trapezoidal Motion [MCT]
  • Continuous Sine Motion [MCS]
  • Hermitic Continuous Movement [MCH]
  • Motion PWM [MP]
  • Free Motor [MF]
  • Motor Wait [MW]
  • Find Direction [FD]
• Light and sound commands
  • LED RGB [L]
  • LED Rainbow [LR]
  • Tone [T]
• Variable read and write commands
  • GET [G]
  • Get Several [GS]
  • Get Several with Header [Gs]
  • Get Wait [GW]
  • Set [S]
  • Save [SV]
  • Reset Variable [RV]
  • Reset variable default value [Rv]
  • Reset Servo [RS]
  • Reset Servo default [Rs]

Motion commands

These are specific commands for the movement and control of the servomotor. The different motions and their curves are explained in more detail in the article on motion curves.

Linear motion [M]

• S12M12000[:1000]

The notation we see for 12000[:1000] indicates that the M command forces one parameter to be passed, but the second parameter is optional. It also tells us that the ':' character is used to separate the parameters. This notation is used for all other commands.

Returning to the command, the M command is a command in which the servomotor moves at constant speed to the end position.

Example:

Trapezoidal motion [MT]

• S12MT12000[:150]:1000;

The MT command is a constant acceleration and deceleration motion calculated based on a fixed acceleration duration.

Example:

Trapezoidal motion 50% [Mt]

• S12Mt12000:1000;

It is the same as MT, but the acceleration time will be half of the total movement time and the deceleration time the other half.

Example:

Accelerated trapezoidal motion [MA]

• S12MA12000[:150]:1000;

It is a trapezoidal movement, but instead of indicating the acceleration time, you indicate the desired acceleration and LibreServo calculates the required acceleration and deceleration time.

Example:

Sine Motion [MS]

• S12MS12000[:150]:1000;

The MS command produces a movement with variable acceleration and deceleration in the form of a sine, hence its name.

Example:

Sine Motion 50% [Ms]

• S12Ms12000:1000;

It is the same as MS, but the acceleration time will be half of the total movement time and the deceleration time the other half.

Example:

Hermitic Movement [MH]

• S12MH12000[:0][:8000][:0]:1000;

As a rule, all movements assume that the servomotor starts a motion from stop and ends stopped, but in this curve we indicate the starting point of movement, the initial speed, the end point and the final speed and LibreServo calculates the entire path. It is ideal for when we want to interrupt a movement and that the servomotor already starts from the speed in which it was, to make complex chained movements ... or to generate different curves to the previous movements.

Example:

Continuous Motion [MC]

• S12MC65535[:1000]

Like Linear Motion, MC behaves in the same way but takes into account the speed of the servomotor and not its position.

Example:

Continuous Trapezoidal Motion [MCT]

• S12MCT65535[:150]:1000;

Example:

Continuous Sine Motion [MCS]

• S12MCS65535[:150]:1000;

Example:

Hermitic Continuous Movement [MCH]

• S12MCH12000[:0][:8000][:0]:1000;

In this command we pass the initial and final velocity of the movement as well as the initial and final acceleration that we want and LibreServo calculates the entire path. It is ideal for when we want to interrupt a movement and that the servomotor already starts from the speed in which it was, to make complex chained movements ... or to generate different curves to the previous movements.

Example:

Motion PWM [MP]

• S12MP500[:1000];

To directly control the PWM of the motor, we use the command MP.

Example:

Free Motor [MF]

• S12MF;

The MF command disables the motor. What it does is to turn off the H-bridge. As soon as another motion command arrives, the H-bridge is automatically enabled.

Example:

Motor Wait [MW]

• S12MW250;

The MW command functions as a Delay. It introduces a wait. It is useful for when we want to send from the same command several tasks that we want to be done separated in time and not one after the other.

Example:

Example:

Light and sound commands

LED RGB [L]

• S12L150:25:210;

The L command controls the color and intensity of the built-in LibreServo RGB LED. Theoretically it could display any color we want.

Example:

LED Rainbow [LR]

• S12LR;

The LR command instructs the LED to start rotating through the colors automatically.

Example:

Tone [T]

• S12T2093:200:50;

The T command attempts to generate a tone using the servo motor itself. No speaker is needed to generate your favorite music! It is recommended to use high frequencies, above 1500Hz, for best performance, sixth or seventh octave onwards depending on each servomotor. At low frequencies it may not sound and instead vibrate the entire servomotor.

Example:

Frequency of musical notes @ciudadpentagrama

Variable read and write commands

Variable read commands are executed from a separate task manager. Within the variables to be recovered, there are RAM variables that are read-only and are not saved after LibreServo is turned off, and there are FLASH variables, which are read and write variables that can be modified and/or saved so that the next time LibreServo is started it will keep the value that we have given it.

The variables are:

GET [G]

• S12G116;

The G command asks LibreServo for an internal parameter/variable that it will return over the serial port. The G command like the rest of the GX commands go in a separate task manager from the main one.

Example:

Get Several [GS]

• S12GS5[,7,8,100,102]:10:500;

The GS command returns not only one variable, but several variables that we want (up to a maximum of 15). In addition, it can be programmed to return the values every X milliseconds.

Example:

Get Several with Header [Gs]

• S12Gs5[,7,8,100,102]:10:500;

The Gs command is the same as the GS command with a difference, it sends us at first a line with the name of all the variables we want separated by commas, this is very useful to get a .csv file output, or to see the variables drawn in the Serial Plotter of Arduino. The Gs command returns not only one variable, but several variables that we want (up to a maximum of 15). In addition, it can be programmed to return the values every X milliseconds.

Example:

Get Wait [GW]

• S12GW250;

The GW command works as a Delay. It introduces a wait in the task manager for reading variables. It is useful for when we want to start receiving data but after a wait to match some specific engine command.

Example:

Set [S]

• S12S111:9600;

With the S command we change the value of LibreServo variables that are writable.

Example:

Save [SV]

• S12SV;

The SV command saves the current LibreServo configuration, the value of the modifiable variables, in the microcontroller Flash, so the configuration will not be lost when the servo motor is turned off.

Example:

Reset variable [RV]

• S12RV116

The RV command returns the value of a variable to the value it has in flash. If the variable was saved just before with the SV command, the variable will have the same value in memory as in flash.

Example:

Reset variable default value [Rv]

• S12Rv116

The Rv command returns the value of a variable to the default value specified in the table. And saves that variable in flash.

Example:

Reset Servo [RS]

• S12RS;

The RS command returns the value of all servomotor variables to the value they have in flash.

Example:

Reset Servo default [Rs]

• S12Rs

The Rs command changes the value of all variables to their default value and saves it in flash.

Example: