add: virtual DAC (100%) and ADC (80%)

upd: makefile

designs/reflectometer_base/adc_model.sv

@@ -0,0 +1,53 @@
+// AN9238 virtual ADC model (1 port)
+
+module virtual_adc_model #(
+    parameter int unsigned ADC_DATA_WIDTH = 12,
+
+    // Bipolar input range: +/- VOLTAGE_RANGE
+    parameter real VOLTAGE_RANGE = 1.0,
+
+    // Analog input correction
+    parameter real VOLTAGE_GAIN  = 0.2,
+    parameter real GROUND_BIAS   = 0.0,
+
+    // ADC timing parameters
+    parameter time CONVERSION_DELAY = 150ps
+)(
+    input  logic                         clk_i,
+    input  real                          voltage_i,
+
+    output logic                         otr_o,
+    output logic [ADC_DATA_WIDTH-1:0]    data_o
+);
+
+    localparam int unsigned ZERO_CODE = (1 << (ADC_DATA_WIDTH - 1));
+    localparam real VOLTAGE_STEP = VOLTAGE_RANGE / real'(ZERO_CODE);
+
+    //------------------------------------------------------------
+    // Convert analog voltage to ADC code TODO: add OTR check
+    //------------------------------------------------------------
+    function automatic real code_to_voltage(
+        input logic [ADC_DATA_WIDTH-1:0] code
+    );
+        return (int'(code) - int'(ZERO_CODE)) * VOLTAGE_STEP;
+    endfunction
+
+    //------------------------------------------------------------
+    // Initial state
+    //------------------------------------------------------------
+    initial begin
+        data_o = ZERO_CODE; // 0V
+        otr_o  = 0;
+    end
+
+    //------------------------------------------------------------
+    // Update analog output
+    //------------------------------------------------------------
+    always @(posedge clk_i) begin
+        #(CONVERSION_DELAY);
+        data_o = ;
+        otr_o = ;
+        
+    end
+
+endmodule