calculate_rfbw.m

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% calculate a channel's complex bandwidth related to the calibration divider value
function [rfbw, caldiv] = calculate_rfbw(pll_rate, caldiv, RxTx, hw)
if strcmp(RxTx, 'Rx')
    channel_factor = 1.4;
    % (1.4 * 2 * pi)/log(2) rounded to the same precision the driver uses
    rounded_factor = 12.6906;
else
    channel_factor = 1.6;
    % (1.6 * 2 * pi)/log(2) rounded to the same precision the driver uses
    rounded_factor = 14.5036;
end

if hw
    % avoid divide by zero on boundary case
    if caldiv == 1
        caldiv = 1 + eps;
    end
    % used to reproduce the divider value (caldiv) we expect on the driver
    rfbw = uint32(fix(((pll_rate - 1)/(caldiv - 1))*(2/rounded_factor)));
else
    % full precision RF bandwidth
    rfbw = round((pll_rate/caldiv)*(2/(channel_factor*(2*pi)/log(2))));
end

% min/max possible values for the RF bandwidth (2x baseband bandwidth) from the
% reference manual (values are in Hz since RFbw is in Hz)
if strcmp(RxTx, 'Rx')
    % Rx: 0.4 MHz <= RF bandwidth <= 56 MHz
    min_rfbw = 400000;
    max_rfbw = 56000000;
else
    % Tx: 1.25 MHz <= RF bandwidth <= 40 MHz
    min_rfbw = 1250000;
    max_rfbw = 40000000;
end

% If the RF bandwidth is outside the range of acceptable values we modify
% the divider value until it falls into an acceptable range.
while (rfbw < min_rfbw) || (rfbw > max_rfbw)
    if (rfbw < min_rfbw)
        caldiv = caldiv - 1;
    else
        caldiv = caldiv + 1;
    end

    if (caldiv < 1) || (caldiv > 511)
        msgbox(sprintf('Calibration divider out of bounds (1 - 511): %i', caldiv), 'Error', 'error');
        return;
    end

    rfbw = calculate_rfbw(pll_rate, caldiv, RxTx, hw);
end