Red Pitaya is a low-cost electronic board featuring Zynq processor that contains both CPU and FPGA. It has been used already for setting up various scientific instruments and provides one of the easiest ways to enter the FPGA world. In our system we used the version called STEMlab 125-14. It has two 14-Bit inputs (LTC2145-14) and two 14-Bit outputs (AD9767) both running at 125 MS/s. Output voltage range is ±1 V and input voltage range can be selected by jumpers to ±1 V or ±20 V. It features also I2C, UART and SPI interfaces and 16 GPIOs. For the communication with client software we use built-in Ethernet port.
For Gwyscope purposes, the standard Red Pitaya API was replaced by our custom built library, as well as the FPGA bitstream, however rest of the ecosystem is still used. A server is running on the Linux OS on the Red Pitaya, using our library to control the FPGA functionality and to connect to additional boards using SPI interface. On processor side, also some of the key functionality, like xy postions generation is performed, to save the FPGA resources.