Servo Motors interfacing with Nexys 4 A7 using Pmod CON3 connector

[Vaishnavi Choudhari]

Hello,

I am a beginner in fpga and I am trying to run mg995 servo motor using Digilent Pmod con3 connector on Nexys 4 A7 fpga Board . I have connected the driver at ja pmod port of the board and have given 5V external DC supply. The motor requires minimum 4.8V to run but I am getting 0V at the output pin(Vs pin) of the driver. I have checked my connections and code but still my servo motor is not running. I have attached my code and constraint file along with the question .

Please help as I am confused whether there is a problem in my motor driver or in code or in the connections.

Thanks in advance!

servo.xpr servo constraints.txt

[JColvin]

Hi @Vaishnavi Choudhari,

Are you providing the pwm signal from one of the Pmod ports on the Nexys A7? Based on the datasheet of the servo motor, https://components101.com/sites/default/files/component_datasheet/MG995-Servo-Motor-Datasheet.pdf, it looks like both the PWM signal and external power supply need to both be in the 4.7 V to 7.2 V range. The Pmod ports on the Nexys A7 only operate at 3.3V CMOS, so that would be why you are not seeing any movement on the servo motor because it is never seeing a logic high input. You would need to use some sort of level shifter to increase the corresponding PWM voltage coming from the Nexys A7.

Let me know if you have any questions.

Thanks,
JColvin