An input system includes an input pen for interfacing with a touchscreen of a display panel. The input pen includes a conductive tip. A switching unit of the pen connects the conductive tip to a receiving unit and a driving unit. The receiving unit receives touchscreen driving signals from the touchscreen through the conductive tip. The driving unit generates pen driving signals transferred to the touchscreen through the conductive tip. The input pen also include a signal processing unit to calibrate timing of the pen driving signal by synchronizing the pen driving signal with the touchscreen driving signal. To enable touch detection, the conductive tip is positioned to contact or approach the touchscreen, the touchscreen driving signal is received from the touchscreen via the conductive tip. The pen driving signal is generated and transferred to the touchscreen via the conductive tip.