DASDUINO AS A SERVO DRIVER
10.Jan.2023
Project author: Domagoj Perković, domagoj.perkovic@donicep.hr
INTRODUCTION
This mini-project shows Dasduino Core as a servo driver, and it is connected via USB to Raspberry Pi which sends information on how to control motors connected to Dasduino. This way, Dasduino power supply through Raspberry is also ensured, as well as communication between them. All digital outputs of the Dasduino can be used for servo motor, except for pins 0 and 1, because they are used for serial communication. Therefore, it is interesting that digital output does not have to have the ability of PWM signal modulation. That way Dasduino can control 12 servo motors. The only thing we should pay attention to is the fact that the servo motor of standard execution can pull around 250mA, so 12 of them would pull 3A which Dasduino can not provide. In that case, you must provide a 5V external power supply of the servo motor.
PROGRAM CODES
Below, you will find the code for Dasduino and Python script for Raspberry Pi.
Dasduino:
// 2018 e-radionica.com// code by Domagoj Perkovic #include int servo_kut;String tmp,servo_motor;Servo myServo2,myServo3,myServo4,myServo5,myServo6,myServo7,myServo8,myServo9,myServo10,myServo11,myServo12,myServo13;void setup() { myServo2.attach(2); // servo pin, does not have to be PWM myServo3.attach(3); // servo pin, does not have to be PWM myServo4.attach(4); // servo pin, does not have to be PWM myServo5.attach(5); // servo pin, does not have to be PWM myServo6.attach(6); // servo pin, does not have to be PWM myServo7.attach(7); // servo pin, does not have to be PWM myServo8.attach(8); // servo pin, does not have to be PWM myServo9.attach(9); // servo pin, does not have to be PWM myServo10.attach(10); // servo pin, does not have to be PWM myServo11.attach(11); // servo pin, does not have to be PWM myServo12.attach(12); // servo pin, does not have to be PWM myServo13.attach(13); // servo pin, does not have to be PWM Serial.begin(9600); // open a serial connection to your computer}void loop() { servo_motor=""; if(Serial.available()>0) { tmp=Serial.readString(); Parser(tmp); Serial.print("["); Serial.print(tmp); Serial.println("]"); Serial.print("["); Serial.print(servo_motor); Serial.println("]"); Serial.print("["); Serial.print(servo_kut); Serial.println("]"); } if(servo_motor.equals("S2")) { myServo2.write(servo_kut); Serial.println("S2"); } else if(servo_motor.equals("S3")) { myServo3.write(servo_kut); Serial.println("S3"); } else if(servo_motor.equals("S4")) { myServo4.write(servo_kut); Serial.println("S4"); } else if(servo_motor.equals("S5")) { myServo5.write(servo_kut); Serial.println("S5"); } else if(servo_motor.equals("S6")) { myServo6.write(servo_kut); Serial.println("S6"); } else if(servo_motor.equals("S7")) { myServo7.write(servo_kut); Serial.println("S7"); } else if(servo_motor.equals("S8")) { myServo8.write(servo_kut); Serial.println("S8"); } else if(servo_motor.equals("S9")) { myServo9.write(servo_kut); Serial.println("S9"); } else if(servo_motor.equals("S10")) { myServo10.write(servo_kut); Serial.println("S10"); } else if(servo_motor.equals("S11")) { myServo11.write(servo_kut); Serial.println("S11"); } else if(servo_motor.equals("S12")) { myServo12.write(servo_kut); Serial.println("S12"); } else if(servo_motor.equals("S13")) { myServo13.write(servo_kut); Serial.println("S13"); } delay(100);}//end loopvoid Parser(String cmd_line){ int x; String kut; cmd_line.trim(); cmd_line.toUpperCase(); x=cmd_line.indexOf(" "); if(x<0) { Serial.println("Kriva naredba..."); return; //there are no spaces, it is an error } else { servo_motor=cmd_line.substring(0,x); kut=cmd_line.substring(x); kut.trim(); servo_kut=kut.toInt(); }}//end ParserPython:
EXAMPLE OF USE
In an example, we will show how to use servo motor connected to pin 2, which is not a PWM pin. Motor connection to the breadboard is seen in the picture.
Servo motor is connected in the following way: red wire to Dasduino +5V, black wire to Dasduino GND and white wire (signal) to Dasduino output 2.
When Dasduino is connected to Raspberry, we must know which communication channel is assigned to it. It is visible if you type the command ls /dev/tty* in the console window which is seen in the following image.
When Python program is launched on the Raspberry, at COM port we must enter the corresponding tty as shown in the following picture (do not forget the full name):
Under Baud rate we enter the speed of serial communication which is defined by Dasduino or, if it is 9600- which is the usual value, just press Enter. After that, the program requests entering a command which consists of servo motor label and the absolute position of the head in degrees, with a space between these two parameters. Sx marks servo motor number and can be between S2 and S13, while the angle is between 0 and 180. S2 if servo motor is connected to digital output 2, S3 if it is connected to digital output 3, and so on.
CONCLUSION
This example is designed in order to enable servo motor startup via serial connection, which ensures application on different devices. In terms of programming, commands travel towards Dasduino via serial connection in the ASCII format which makes communication applicable on different platforms. It is even possible to connect directly to Dasduino’s serial communication pins and that way issue commands – you do not have to use USB cable or USB-UART converter on the Dasduino board. Raspberry Pi is used in this example, but you can also use PC, Mac, Microbit or an ordinary terminal. By modifying Python program, different applications of servo motor can be obtained, without changing Dasduino program, i.e. we can practically perceive it as a “black box” which receives commands and executes them. This way, it is possible for users who do not have developing Dasduino/Arduino environment, or who do not know how to use it, to use servo motors with other devices and other program languages. There is another reason to use Dasduino as a servo driver: namely, Dasduino Core is almost two times cheaper than other modules for servo motor control of similar purpose and use.
