Introduction: FPGA Cyclone IV DueProLogic Controls Servo Motor
In this tutorial, we are going to write Verilog code to control servo motor. The servo SG-90 is manufactured by Waveshare. When you buy the servo motor, you may receive a datasheet that lists the operating voltage, maximum torque and the proposed Pulse Width Modulation (PWM)...etc. However, the FPGA DuePrologic provides input voltage of 3.3V where the operating voltage of servo SG-90 is 5V - 7V. In the lack of electrical power, I will list my calibrated PWM in order to rotate the servo motor successfully.
Our task: The servo motor is rotated back and forth with the period of 5 seconds
Full menu: https://roywchpi.blogspot.com/2020/07/13-fpga-cyclone-iv-dueprologic-controls.html
Step 1: Build Electronic Circuit
Step 2: Set Up Pin Planner
Click "Start I/O Assignment Analysis" to check if the pin planner is set correctly. Otherwise, you have to import all port names by yourself.
Step 3: Verilog Code
We create a timer "servo_count". When "servo_A" is HIGH, the PWM is 1.5ms and hence the servo is located at 120 deg. In contrast, when "servo_A" is LOW, the PWM is 0.15ms and therefore the servo is stayed at 0 degree.
assign XIO_2[3] = servo_pulse; //for V'
reg [31:0] servo_count;
initial begin
servo_count <= 32'b0;
servo_A <= 1'b0;
end
always @(posedge CLK_66)
begin
servo_count <= servo_count + 1'b1;
if(servo_count > 400000000) //Clock cycle 66MHz, 1/66M * 400000000 ~ 5 seconds
begin
servo_A <= !servo_A;
servo_count <= 32'b0;
end
end
reg [31:0] ex_auto;
initial begin
ex_auto <= 32'b0;
servo_auto <= 1'b0;
end
always @(posedge CLK_66)
begin
if(servo_A==1'b1)
begin
ex_auto <= ex_auto + 1'b1;
if(ex_auto > 100000) //Clock cycle 66MHz, this PWM is ~1.5ms, servo rotates to 120 deg
begin
servo_auto <= !servo_auto;
ex_auto <= 32'b0;
end
end
if(servo_A==1'b0)
begin
ex_auto <= ex_auto + 1'b1;
if(ex_auto > 10000) //Clock cycle 66MHz, this PWM is ~0.15ms, servo rotates to 0 deg
begin
servo_auto <= !servo_auto;
ex_auto <= 32'b0;
end
end
end
Step 4: Upload Verilog Code
Click "Start Compilation". If no error message is displayed, go to "Programmer" to complete hardware setup. Remember to update the pof file in "Change file" if necessary. The click "Start" to upload the code.
After all, you should see that the servo motor is rotated periodically.
