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EVNServo

EVNServo#

EVNServo is a class for controlling 3-wire hobby (RC) servo motors. However, the servo can be disabled using the user button similar to EVNMotor. Additionally, EVNServo uses timer-generated interrupts to write to the servo motor, allowing for smooth sweeping motion at various speeds without the need for delay(). The default settings are for the Fixed Servo Standard Peripherals we sell, the Geekservo 270deg Servo, but this library is compatible with any fixed range servo.

Note

Each instance of EVNServo (4 max) consumes 1 of the RP2040’s 8 PIO state machines, so keep this in mind if you are using PIO for your own purposes.

Note

EVNServo consumes some of the RP2040’s spinlock peripherals. See this page for more info.

Warning

Geekservo servos can receive pulses from 500-2500us, but it is possible to damage certain servos by writing pulses outside their allowed ranges. If you are using a new servo, consider checking the servo instructions and specs to see if there is a rated pulse range given, and if there aren’t any, try starting by setting min_pulse and max_pulse to 1000 and 2000 respectively.

Wiring (Servo)#

Host

Peripheral

Description

SIG

SIG (Yellow)

Signal

5V

VCC (Red)

5V Power

GND

GND (Brown)

Ground (0V)

Constructor#

class EVNServo(uint8_t port, bool servo_dir = DIRECT, uint16_t range = 270, float start_position = 135, uint16_t min_pulse_us = 600, uint16_t max_pulse_us = 2400, float max_dps = 500)#
Parameters

  • port – Port the servo is connected to (1 - 4)

  • servo_dir – Direction of rotation of motor shaft. On Geekservo, DIRECT is clockwise. Defaults to DIRECT

  • range – Angular range of servo (in degrees). Defaults to 270

  • start_position – Starting position of motor shaft when servo is initialised (in deg). Defaults to 135

  • min_pulse_us – Minimum pulse time sent to the servo motor (in microseconds). Defaults to 600

  • max_pulse_us – Maximum pulse time sent to the servo motor (in microseconds). Defaults to 2400

  • max_dps – Maximum angular rotation of servo shaft (in degrees per second). Defaults to 500

Example Usage:

EVNServo servo(1);

//Geekservo 2kg 360Deg Servo
EVNServo servo2(2, 0, DIRECT, 360, 600, 2400, 428);

Functions#

void begin()

Initializes servo. Call this function before calling the other EVNServo functions.

EVNServo servo(1);

void setup1()   //call on setup1() for best performance!
{
    servo.begin();
}

Note

For best performance, run this on the 2nd core using void setup1()

float getMaxDPS()
Returns

Maximum angular rotation of servo shaft (in degrees per second).

float max_dps = servo.getMaxDPS();
uint16_t getRange()
Returns

Angular range of servo (in degrees).

int range = servo.getRange();
void write(float position, uint16_t wait_time_ms, float dps)

Rotate motor shaft to given angular position.

Parameters

  • position – Position to run servo shaft to (in degrees)

  • wait_time_ms – Time to wait before continuing the program (in milliseconds). Same effect as delay(), but terminates when servos are disabled.

  • dps – Speed to run servo at (in degrees per second), from 0 to max_range. When dps is 0, servo runs at max speed. Defaults to 0.

//write servo to run to 180 degrees at a speed of 30DPS, and wait 6 seconds
servo.write(180, 6000, 30);
void writeMicroseconds(uint16_t pulse_us, uint16_t wait_time_ms)

Sends pulse of given length to servo.

Parameters

  • pulse_us – Pulse time to transmit to servo (in microseconds) from 200us to 2800us

  • wait_time_ms – Time to wait before continuing the program (in milliseconds). Same effect as delay(), but terminates when servos are disabled.

//write 1500us pulse to servo, and wait 3 seconds
servo.writeMicroseconds(1500, 3000);
void setMode(bool enable)

Enable/disable servo. When disabled, the servo will no longer hold its position, and the PIO state machine consumed by the EVNServo object is released.

Parameters

enable – Whether to enable servo operation

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