To control PIN-Diode switches a controller is used which provides the necessary bias voltages for the diodes. The controller has a serial interface connected to the USB-Bus.
During the design process eight card drivers, each with eight outputs, were considered. A total number up to 64 PIN-Diodes can be driven with a single controller. An Atmega16 microcontroller was used.
The system concept consists of a controller and its driver boards.
Each driver board has a data line, so that the controller can transmit in each cycle one byte on the bus. Each driver takes his bit from the bus. After eight cycles the data is loaded into the shift register.
The controller offers an external trigger input which can be used to execute previously stored program step by step. The input is TTL compatible with a nominal voltage of 5 V. A rising edge triggers an external trigger if the input is activated. The status of the trigger input is displayed on the trigger LED. If the input is activated, it can be triggered by a rising edge trigger. If the LED is switched off, then the input is disabled.
In order to synchronize additional measurement devices with the PIN-Diode controller, the controller emits a TTL pulse with a minimum time period of 50μs at the TRIG-Out connector. In this way, a measurement can be started directly after the switching. This output can not be turned off.