I have an issue with my code.
I'm trying to swap between Xspeed and Yspeed at the same clock while the if statement is true.
I'm getting the errors:
cant resolve multiple constant drivers for net
and
constant drivers at module_name
Several if statements show the same errors.
int Xspeed, topLeftX_FixedPoint; // local parameters
int Yspeed, topLeftY_FixedPoint;
//////////--------------------------------------------------------------------------------------------------------------=
// calculation 0f Y Axis speed using gravity or colision
always_ff@(posedge clk or negedge resetN)
begin
if(!resetN) begin
Yspeed <= INITIAL_Y_SPEED;
topLeftY_FixedPoint <= INITIAL_Y * FIXED_POINT_MULTIPLIER;
end
else begin
// colision Calcultaion
//hit bit map has one bit per edge: Left-Top-Right-Bottom
if ((collision && HitEdgeCode [2] == 1 && HitEdgeCode[1]==1)) begin // hit top border of brick
if (Yspeed < 0 && Xspeed > 0) begin // while moving up and moving right
Yspeed <= Xspeed ;
Xspeed <= Yspeed ; // negative move left
end
end
The full the code:
// (c) Technion IIT, Department of Electrical Engineering 2021
//-- Alex Grinshpun Apr 2017
//-- Dudy Nov 13 2017
// SystemVerilog version Alex Grinshpun May 2018
// coding convention dudy December 2018
// updaed Eyal Lev Feb 2021
module pokadoor_moveCollision (
input logic clk,
input logic resetN,
input logic startOfFrame, // short pulse every start of frame 30Hz
input logic Y_direction, //change the direction in Y to up
input logic toggleX, //toggle the X direction
input logic collision, //collision if smiley hits an object
input logic [3:0] HitEdgeCode, //one bit per edge
output logic signed [10:0] topLeftX, // output the top left corner
output logic signed [10:0] topLeftY // can be negative , if the object is partliy outside
);
// a module used to generate the ball trajectory.
parameter int INITIAL_X = 320;
parameter int INITIAL_Y = 240;
parameter int INITIAL_X_SPEED = 60;
parameter int INITIAL_Y_SPEED = 150;
parameter int MAX_Y_SPEED = 230;
const int Y_ACCEL = -1;
const int FIXED_POINT_MULTIPLIER = 64;
// FIXED_POINT_MULTIPLIER is used to enable working with integers in high resolution so that
// we do all calculations with topLeftX_FixedPoint to get a resolution of 1/64 pixel in calcuatuions,
// we devide at the end by FIXED_POINT_MULTIPLIER which must be 2^n, to return to the initial proportions
const int x_FRAME_SIZE = 639 * FIXED_POINT_MULTIPLIER; // note it must be 2^n
const int y_FRAME_SIZE = 479 * FIXED_POINT_MULTIPLIER;
const int bracketOffset = 30;
const int OBJECT_WIDTH_X = 64;
int Xspeed, topLeftX_FixedPoint; // local parameters
int temp;
int Yspeed, topLeftY_FixedPoint;
//////////--------------------------------------------------------------------------------------------------------------=
// calculation 0f Y Axis speed using gravity or colision
always_ff@(posedge clk or negedge resetN)
begin
if(!resetN) begin
Yspeed <= INITIAL_Y_SPEED;
topLeftY_FixedPoint <= INITIAL_Y * FIXED_POINT_MULTIPLIER;
end
else begin
// colision Calcultaion
//hit bit map has one bit per edge: Left-Top-Right-Bottom
if ((collision && HitEdgeCode [2] == 1 && HitEdgeCode[1]==1)) begin // hit top border of brick
if (Yspeed < 0 && Xspeed > 0) begin // while moving up and moving right
Yspeed <= Xspeed ;
Xspeed <= Yspeed ; // negative move left
end
end
if ((collision && HitEdgeCode [2] == 1 && HitEdgeCode[3]==1)) begin // hit top border of brick
if (Yspeed < 0 && Xspeed < 0) begin // while moving up and moving left
Yspeed <= -Xspeed ;
Xspeed <= -Yspeed ; // negative move left
end
end
if ((collision && HitEdgeCode [2] == 1 && HitEdgeCode[3]==0 && HitEdgeCode[1]==0)) begin // hit top border of brick
if (Yspeed < 0) begin// while moving up
Yspeed <= -Yspeed ;
end
end
////
if ((collision && HitEdgeCode [0] == 1 && HitEdgeCode[1]==1)) begin// || (collision && HitEdgeCode [1] == 1 )) hit bottom border of brick
if (Yspeed > 0 && Xspeed > 0) begin// while moving down and moving right
Yspeed <= -Xspeed ;
Xspeed <= -Yspeed ;
end
end
if ((collision && HitEdgeCode [0] == 1 && HitEdgeCode[3]==1)) begin// || (collision && HitEdgeCode [1] == 1 )) hit bottom border of brick
if (Yspeed > 0 && Xspeed < 0) begin// while moving down and moving left
Yspeed <= Xspeed ;
Xspeed <= Yspeed ;
end
end
if ((collision && HitEdgeCode [0] == 1 && HitEdgeCode[3]==0 && HitEdgeCode[1]==0 )) begin// || (collision && HitEdgeCode [1] == 1 )) hit bottom border of brick
if (Yspeed > 0 ) begin// while moving down
Yspeed <= -Yspeed ;
end
end
// perform position and speed integral only 30 times per second
if (startOfFrame == 1'b1) begin
topLeftY_FixedPoint <= topLeftY_FixedPoint + Yspeed; // position interpolation
if (Yspeed < MAX_Y_SPEED ) // limit the spped while going down
Yspeed <= Yspeed - Y_ACCEL ; // deAccelerate : slow the speed down every clock tick
if (Y_direction) begin // button was pushed to go upwards
if (Yspeed > 0 ) // while moving down
Yspeed <= -Yspeed ; // change speed to go up
end ;
end
end
end
//////////--------------------------------------------------------------------------------------------------------------=
// calculation of X Axis speed using and position calculate regarding X_direction key or colision
always_ff@(posedge clk or negedge resetN)
begin
if(!resetN)
begin
Xspeed <= INITIAL_X_SPEED;
topLeftX_FixedPoint <= INITIAL_X * FIXED_POINT_MULTIPLIER;
end
else begin
// an edge input is tested here as it is a very short instance
//if (toggleX)
//Xspeed <= -Xspeed;
// collisions with the sides
if (collision && HitEdgeCode [3] == 1 && HitEdgeCode[0] ==0 && HitEdgeCode[2]==0) begin
if (Xspeed < 0 ) // while moving left
Xspeed <= -Xspeed ; // positive move right
end
if (collision && HitEdgeCode [1] == 1 && HitEdgeCode[0] ==0 && HitEdgeCode[2]==0 ) begin // hit right border of brick
if (Xspeed > 0 ) // while moving right
Xspeed <= -Xspeed ; // negative move left
end
if (startOfFrame == 1'b1 )//&& Yspeed != 0)
topLeftX_FixedPoint <= topLeftX_FixedPoint + Xspeed;
end
end
//get a better (64 times) resolution using integer
assign topLeftX = topLeftX_FixedPoint / FIXED_POINT_MULTIPLIER ; // note it must be 2^n
assign topLeftY = topLeftY_FixedPoint / FIXED_POINT_MULTIPLIER ;
endmodule
The error:
Error (10028): Can't resolve multiple constant drivers for net "Xspeed[31]" at pokadoor_moveCollision.sv(139) Error (10029): Constant driver at pokadoor_moveCollision.sv(62) Error (10028): Can't resolve multiple constant drivers for net "Xspeed[30]" at pokadoor_moveCollision.sv(139) Error (10028): Can't resolve multiple constant drivers for net "Xspeed[29]" at pokadoor_moveCollision.sv(139) Error (10028): Can't resolve multiple constant drivers for net "Xspeed[28]" at pokadoor_moveCollision.sv(139) Error (10028): Can't resolve multiple constant drivers for net "Xspeed[27]" at pokadoor_moveCollision.sv(139) Error (10028): Can't resolve multiple constant drivers for net "Xspeed[26]" at pokadoor_moveCollision.sv(139) Error (10028): Can't resolve multiple constant drivers for net "Xspeed[25]" at pokadoor_moveCollision.sv(139) Error (10028): Can't resolve multiple constant drivers for net "Xspeed[24]" at pokadoor_moveCollision.sv(139) Error (10028): Can't resolve multiple constant drivers for net "Xspeed[23]" at pokadoor_moveCollision.sv(139) Error (10028): Can't resolve multiple constant drivers for net "Xspeed[22]" at pokadoor_moveCollision.sv(139) Error (10028): Can't resolve multiple constant drivers for net "Xspeed[21]" at pokadoor_moveCollision.sv(139) Error (10028): Can't resolve multiple constant drivers for net "Xspeed[20]" at pokadoor_moveCollision.sv(139) Error (10028): Can't resolve multiple constant drivers for net "Xspeed[19]" at pokadoor_moveCollision.sv(139) Error (10028): Can't resolve multiple constant drivers for net "Xspeed[18]" at pokadoor_moveCollision.sv(139) Error (10028): Can't resolve multiple constant drivers for net "Xspeed[17]" at pokadoor_moveCollision.sv(139) Error (10028): Can't resolve multiple constant drivers for net "Xspeed[16]" at pokadoor_moveCollision.sv(139) Error (10028): Can't resolve multiple constant drivers for net "Xspeed[15]" at pokadoor_moveCollision.sv(139) Error (10028): Can't resolve multiple constant drivers for net "Xspeed[14]" at pokadoor_moveCollision.sv(139) Error (12152): Can't elaborate user hierarchy "Pokadoor_Block_bdf:inst14|pokadoor_moveCollision:inst" Error: Quartus Prime Analysis & Elaboration was unsuccessful. 20 errors, 15 warnings Error: Peak virtual memory: 4797 megabytes Error: Processing ended: Thu Apr 14 14:26:35 2022 Error: Elapsed time: 00:00:07 Error: Total CPU time (on all processors): 00:00:16
Those error messages are not very specific. You can get more helpful messages from other simulators, such as the ones on edaplayground (Cadence and Synopsys).
The problem is that you must not assign to the same signal from different always_ff blocks. For example, your code assigns to Xspeed from both always_ff blocks.
Refer to IEEE Std 1800-2017, section 9.2.2.4 Sequential logic always_ff procedure:
Variables on the left-hand side of assignments within an always_ff procedure, including variables from the contents of a called function, shall not be written to by any other process.
You must restructure your code such that all assignments to Xspeed are done in the same always_ff block.