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Servo controller in verilog. Takes an 8-bit position and converts it into the pwm signal required by a servo motor.
/*
servo controller
Based on code from Mojo tutorial
https://embeddedmicro.com/tutorials/mojo/servos
Takes an 8-bit position as an input
Output a single pwm signal with period of ~20ms
Pulse width = 1ms -> 2ms full scale. 1.5ms is center position
*/
module servo_controller (
input clk,
input rst,
input [7:0] position,
output servo
);
reg pwm_q, pwm_d;
reg [19:0] ctr_q, ctr_d;
assign servo = pwm_q;
//position (0-255) maps to 50,000-100,000 (which corresponds to 1ms-2ms @ 50MHz)
//this is approximately (position+165)<<8
//The servo output is set by comparing the position input with the value of the counter (ctr_q)
always @(*) begin
ctr_d = ctr_q + 1'b1;
if (position + 9'd165 > ctr_q[19:8]) begin
pwm_d = 1'b1;
end else begin
pwm_d = 1'b0;
end
end
always @(posedge clk) begin
if (rst) begin
ctr_q <= 1'b0;
end else begin
ctr_q <= ctr_d;
end
pwm_q <= pwm_d;
end
endmodule
@bussss
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bussss commented May 4, 2019

hello, How do I write the test bench of this code?,Please, help me.

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