/* * Debouncer chip on Wokwi - Proof of Concept. * * Author: Tim Mathias * */ module wokwi #( parameter CLOCK_PERIOD_ns = 100000, // nanoseconds. parameter DEBOUNCE_PERIOD_ms = 10 // milliseconds. ) ( input wire clock, input wire in, // Synchronous and noisy input. // Optional outputs. output reg out, // Debounced and filtered output. output reg edj, // Goes high for 1 clock cycle on either edge of output. Note: used "edj" because "edge" is a keyword. output reg rise, // Goes high for 1 clock cycle on the rising edge of output. output reg fall // Goes high for 1 clock cycle on the falling edge of output. ); //function integer MinBitWidth([1023:0] value); // begin // for (MinBitWidth = 0; value > 0; MinBitWidth = MinBitWidth + 1) // begin // value = value >> 1; // end // end //endfunction localparam MAX_COUNT_32BITS = DEBOUNCE_PERIOD_ms * 1_000_000 / CLOCK_PERIOD_ns - 2; // Default type of 32-bits. Subtract 2 because we will be counting down to -1, i.e. when borrow flag is set. //localparam COUNTER_BITS = MinBitWidth(MAX_COUNT_32BITS); // Calculate actual bit width needed. localparam COUNTER_BITS = 16; // Specify actual bit width needed. //typedef logic [COUNTER_BITS - 1 : 0] TCounter; //localparam TCounter MAX_COUNT = MAX_COUNT_32BITS; // Assign to a type of the actual bit width (truncation warning from Quartus). localparam [15 : 0] MAX_COUNT = MAX_COUNT_32BITS; // Assign to a type of the actual bit width (truncation warning from Quartus). //localparam TCounter ONE = 1; localparam [15 : 0] ONE = 1; //typedef logic [COUNTER_BITS : 0] TBorrowCounter; // Extra bit for borrow flag. //TBorrowCounter borrow_counter; reg [16 : 0] borrow_counter; //logic borrow; reg borrow; wire w_edj; wire w_rise; wire w_fall; initial begin out = 0; end always @(posedge clock) begin borrow_counter[COUNTER_BITS] <= 0; // Clear the borrow flag. borrow_counter[COUNTER_BITS - 1 : 0] <= MAX_COUNT; // Freeze counter by default to reduce switching losses when input and output are equal. edj <= 0; rise <= 0; fall <= 0; if (borrow) // If successfully debounced, notify what happened. begin out <= in; edj <= w_edj; // Goes high for 1 clock cycle on either edge. rise <= w_rise; // Goes high for 1 clock cycle on the rising edge. fall <= w_fall; // Goes high for 1 clock cycle on the falling edge. end else if (in != out) // Hysteresis. begin borrow_counter <= borrow_counter - ONE; // Only decrement when input and output differ. end end assign borrow = borrow_counter[COUNTER_BITS]; // Edge detect. assign w_edj = in ^ out; assign w_rise = in & ~out; assign w_fall = ~in & out; endmodule