PL2303HXD / EA / RA has 8 software controllable "General Purpose Input Output, GPIO" control signals pin, you can use this API to control. Direction: input or output. Logic level: high or low. GPIO Pin define: 1. Gp0. 2. Gp1. 3. Gp2. 4. Gp3. 5. Gp4-ri. 6. Gp5-dcd. 7. Gp6-dsr.