Max 10 ADC Simulation - Can't get it to work properly

I'm using Modelsim though the simulator used doesn't make any difference.

In the Max 10 implementation, the ADC pins aren't exposed in the verilog code so you can't access them directly to feed in a signal which is unfortunate. If it was written differently then for simulation only, then you could have a real data type signal as input to represent the analogue value.

There is lots you can do in a test bench to model analogue stuff. In the past I modelled the currents in the inductor of buck switcher which was being controlled by an FPGA. It enabled me to do a complete end to end sim. The analogue stuff was crude but good enough for what I needed.

Here is a brief code snippet of the test bench to give you an idea, don't worry about the details of what it does, just get a feel. It recalcs the currents every nanosecond.

    localparam voltagediffpos = 22.0;
    localparam voltagediffneg = 2.0;
    localparam inductance = 3.5E-6;
    localparam fullscalecurrent = 11.0;
    localparam voltagelaser = 1.3;
    localparam resistancelaser = 0.05;
    localparam capacitancecapacitor = 10E-6;
    real current_inductor ;
    real current_laser_capacitor ;
    real current_laser;
    real current_target ;
    real voltage_capacitor ;
    integer j;
    
    initial begin
        for (j = 0; j < 16; j = j + 1) begin
            current_inductor <= 0.0;
            current_laser_capacitor <= 0.0;
            current_laser <= 0.0;
            current_target <= 0.0;
            voltage_capacitor <= 0.0;
        end
    end
    
    genvar i;
    
    generate
        for (i = 0; i < 16; i = i + 1) begin: current_calc
            always begin
           # 1
                current_target <= $itor(voltages)*fullscalecurrent/4096.0; 
                current_laser_capacitor <= (short_fet) ? 0.0 : current_inductor;
                if (buck_fet) begin
                    current_inductor <= current_inductor + voltagediffpos*1E-9/inductance;
                end else begin
                    if ((current_inductor - voltagediffneg*1E-9/inductance) > 0) begin
                        current_inductor <= current_inductor - voltagediffneg*1E-9/inductance;
                    end else begin
                        current_inductor <= 0.0;
                    end
                end
                
                if (short_fet) begin
                    voltage_capacitor <= 0.0;
                    current_laser <= 0.0;
                end else begin
                    if (voltage_capacitor < voltagelaser) begin
                        current_laser <= 0.0;
                    end else begin
                        current_laser <= (voltage_capacitor - voltagelaser) / resistancelaser;
                    end
                    voltage_capacitor <= voltage_capacitor + (current_laser_capacitor - current_laser) * 1E-9 / capacitancecapacitor;
                end
            end
            
            assign comparitor = (current_laser_capacitor > current_target);
        end
    endgenerate