function up_down(a, u, up, down)
        height = readDistance(u)*38
        F1 = 'D2';
        B1 = 'D4';
        F2 = 'D7';
        B2 = 'D8';
        F3 = 'D11';
        B3 = 'D12';
        E1 = 'D3';
        E2 = 'D6';
        E3 = 'D10';

        height_change = height - 0.923        
        if up == 1
            writePWMVoltage(a, 'D3', 2);
            writePWMVoltage(a, 'D6', 3);
            writePWMVoltage(a, 'D10', 2);

            writeDigitalPin(a, F1, 0);
            writeDigitalPin(a, B1, 1);
            writeDigitalPin(a, F2, 0);
            writeDigitalPin(a, B2, 1);
            writeDigitalPin(a, F3, 0);
            writeDigitalPin(a, B3, 1);
            pause(0.2);
            writeDigitalPin(a, F1, 0);
            writeDigitalPin(a, B1, 0);
            writeDigitalPin(a, F2, 0);
            writeDigitalPin(a, B2, 0);
            writeDigitalPin(a, F3, 0);
            writeDigitalPin(a, B3, 0);
        end
        if down == 1
            writePWMVoltage(a, 'D3', 1*height_change);
            writePWMVoltage(a, 'D6', 1.2*height_change);
            writePWMVoltage(a, 'D10', 1*height_change);

            writeDigitalPin(a, F1, 1);
            writeDigitalPin(a, B1, 0);
            writeDigitalPin(a, F2, 1);
            writeDigitalPin(a, B2, 0);
            writeDigitalPin(a, F3, 1);
            writeDigitalPin(a, B3, 0);
            pause(0.1);
            writeDigitalPin(a, F1, 0);
            writeDigitalPin(a, B1, 0);
            writeDigitalPin(a, F2, 0);
            writeDigitalPin(a, B2, 0);
            writeDigitalPin(a, F3, 0);
            writeDigitalPin(a, B3, 0);
         
            clear a
            clear u
end