Serial Port and General-Purpose I/O Lines

The EM200 features a serial port (RX, TX lines), plus nine general-purpose I/O lines (GPIO0~GPIO8). All of these lines are of the CMOS type. The maximum load current for each I/O line is 10mA.

The serial port of the EM200 can work in one of the three modes: UART, Wiegand, or clock/data. All three modes are described in detail in the documentation for the ser. object.

The simplified structure of the EM200's I/O lines is shown in the circuit diagram below. All lines are "quasi-bidirectional" and can be viewed as open collector outputs with a weak pull-up resistor. There is no explicit direction control. To "measure" an external signal applied to a pin, the OUT line must first be set to HIGH. It is OK to drive the pin LOW externally when the pin outputs HIGH internally.  

A circuit diagram of an EM200 GPIO line.

I/O line control is described in detail in the documentation for the io. object.