Gwyscope DSP is a shorthand for three boards combo:

• Red Pitaya STEMlab 125-14 (PCB Red Pitaya)
• Mainboard (PCB CMIPITAYA)
• HRDAC board (PCB CMIDAC11001)

Although we designed the boards to be connected in a stack to enhance capabilities of the Red Pitaya (RP), other use cases are possible. For example only RP board and Mainboard might be used to enhance RP with many channels high bit-depth converters or the 20-bit DAC board can also be controlled by just an Arduino.

The DSP is open hardware, i.e. source files (in KiCAD format) that can be used for Mainboard and HRDAC board manufacturing were made publicly available. Note that some parts are marked as DNP (Do Not Place) because two assembly variants are possible. All boards can be connected together to form a stack or the HRDAC board can be connected as a standalone board.

• In the stack configuration RP is connected to the Mainboard by using two 26-wire flat ribbon cables and four SMA – U.FL cables. Use a suitable combination of spacer sleeves and washers to separate centers of the Mainboard and the HRDAC board by 3 x 5.08 = 15.24 mm. Such a stack is then compatible with a standard Eurocard rack. For J8 and J9 connectors we recommend to use rectangular connectors (e.g. J8 and J9) soldered from the bottom side of the Mainboard. Analog signals from the HRDAC board are connected via SMB connectors. Place SMB Jacks on the bottom side of the Mainboard and SMB plugs on top side of the HRDAC board.

• In the standalone configuration the RP is connected to the Mainboard the same way as described above, the HRDAC board is separately. For J8 and J9 connectors on the Mainboard, please use standard Molex and IDC connectors that are the same as on the HRDAC board. The digital communication between the Mainboard and the HRDAC board is accomplished by a 10-wire flat ribbon cable. To connect analog signals from the HRDAC board using cables, SMA or SMB connectors can be used. The SMB connectors on the Mainboard remain unpopulated.

The Red Pitaya board can be bought e.g. from Digikey, search for the IZD0007 product number. This is the older version with Zync 7010 chip. An upgraded board (IZD0029) exists employing more advanced Zync 7020, however we have only (successfully) tried to compile a bitstream for it without any further testing. Nevertheless, our plan is to move to this board in the future. For the OS version we use the latest stable 1.04-18 version, the newer 2.0 versions are untested.

The standard jumper setting that we use in our labs is the low voltage configuration (±1 V), nevertheless RP can be configured for a high voltage range (±20 V).

The mainboard (PCB CMIPITAYA) is used to provide power supply for RP, it has two 18-bit 8ch ADCs, 16-bit 16ch DAC, input and output voltage buffers, two multiplexers, one CS decoder and one IO expander. It has Eurocard format (160 mm x 100 mm). Since DPS V5 there are jumpers available that allow for bypassing the input and output buffer, so the original RP bandwidth can be restored. The power is supplied by either two Molex connectors (since PCB V6) or a 96 pin EURO connector (DIN 41612), see the image below. This right-angle or this straight connectors can be used as counterparts.

The most important signals on this connector are the ADC_MUX1-16 which go to the 18-bit ADCs and also via multiplexers and buffers to RP's fast inputs. Further, AUX_DAC_OUT1-16 signals connect with the 16-bit DAC, SCAN_DAC_* signals are just feed-through pins when the 20-bit DAC board is connected and RP1_FAST_DAC signals are RP's fast outputs.

This board provides three 20-bit DACs in Daisy-chain configuration and has also the same Eurocard format as the Mainboard. It was designed as an independent board, so it has a Molex connector for power supply and a 10-pin (since V5) IDC connector for digital communication. Counting from “left” the first two DACs are the same, but the third DAC can be jumper configured for standalone operation. There are a few more jumpers, most important are the ones that are used to set the output voltage range. Lets explain the settings on OUT1 (most left) DAC. Jumper J11 is used to switch between symmetric or positive output voltage. In lower position as shown in the image below, symmetric voltage is generated. Furthermore, jumper J1 controls if the reference voltage (+5 V) is multiplied by two or not. In presented setting the reference voltage is doubled, i.e. in this configuration the output voltage range is set to ±10 V.