None of the pins work as inputs
Sounds like there's a basic misunderstanding here.
Setting a pin as &quot;output&quot; mean it'll either supply +5V (&quot;HIGH&quot;) or 0V (&quot;LOW&quot;). Both those states are considered &quot;outputs&quot;, and the pin can source or sink current in those states. When driven &quot;LOW&quot;, the circuit does &quot;input&quot; current to the chip, but that's not what &quot;input&quot; usually means.
&quot;Input&quot; means you can use the pin to read the voltage applied to the pin. When connected to a PWM source, this might manifest as the pin quickly switching between &quot;1&quot; / &quot;HIGH&quot; / &quot;+5V&quot; and &quot;0&quot; / &quot;LOW&quot; / &quot;0V&quot;.
Normally, you would use the &quot;input&quot; mode to read things like switches, or potentiometers on the analog input pins.
Your desired use of &quot;current input&quot; pins will require you to configure the pin as &quot;output&quot;, and then set it to &quot;LOW&quot;, which will make it able to sink current.