Summer of FPGAs - Building an Embedded System on FPGA

That's great! Yeah, it truly fascinates me when we can actually change the hardware which is not possible in the case of microcontrollers.

The LCD is a bit problematic in the beginning because it's a bit hard to debug where the loose contact is, but eventually, you'll figure it out!

Works in charm! After this, I made the sw_in pin external and mapped the same to PIN2 of the Pmod by uncommenting and adding sw_in on the .xdc file.

True. The real beauty is that now the hardware has got configured(quadrature decoder) with additional input switch parameter by what it seems like a software tweak(verilog file). Btw, Vivado is hiding a lot of stuff

The LCD is showing up like this. Seems like a familiar loose contact issue in these type of parallel display interfaces. I'll check back the hardware wiring -- had rushed with the soldering process.

Oh yes. We need to modify the Quadrature Decoder hardware.

module Quad_Decode (clk, rot_en_A, rot_en_B, direction, count, sw_in);

input clk, rot_en_A, rot_en_B, sw_in;

output reg direction;

output [7:0] count;

reg [2:0] rot_en_A_delayed, rot_en_B_delayed;

always @(posedge clk)

begin

rot_en_A_delayed <= {rot_en_A_delayed[1:0], rot_en_A};

end

always @(posedge clk)

begin

rot_en_B_delayed <= {rot_en_B_delayed[1:0], rot_en_B};

end

wire count_enable = rot_en_A_delayed[1] ^ rot_en_A_delayed[2] ^ rot_en_B_delayed[1] ^ rot_en_B_delayed[2];

wire count_direction = rot_en_A_delayed[1] ^ rot_en_B_delayed[2];

reg [7:0] count;

always @(posedge clk)

begin

  if(count_enable)

  begin

    if(count_direction)

    begin

      direction <= 1;

      count <= count + 1;

    end

    else

    begin

      direction <= 0;

      count <= count - 1;

    end

  end

  else

   begin

     if (!sw_in)

     count <= 0;

  end

end

endmodule

Connect the switch directly to the Quad_Decode module in block design.

I guess this should do.

Again on Arty-S7, the rotary thing works fine the same way.

I tried to add another parameter "Status" which would detect if the user presses the rotary encoder's central switch so as to set the value back to 0 at any point. So, added a new AXI_GPIO 1 bit wide to read SW pin of rotary encoder and took that parameter into the same while loop with if(status == 0). It was just a lame idea of trying to make it, I realized after running the program.

The status does flip to 0 and so does the count. But when the switch is released, Status turns back to 1 as expected and counter resumes from the same point where it was before pressing that switch. Rather it was expected to start back from 0. So for this, would tweaking the quad_decode.v and adding in a new parameter to reset the full counter help? Any clues?

That's great navadeepganeshu! I hope you'll enjoy the upcoming modules in the series too!