Obsidian is a FPGA carrier board in development, designed to interface with ADC and DAC devices, either stand-alone or as an I/O expansion board for Marble.
The design files here were created with KiCad version 9.0.0-rc3.
- Xilinx XC7A50T-1CSG325C FPGA
- Arduino shield compatible, like the Digilent Arty
- SPI flash boot
- DDR3 memory chip
- FTDI USB interface
- 2 direct LEDs
- 1 GigE port (PoE?)
- 6 Pmod ports (3.3V)
- MS5351M or SI5351A or similar for GTP frequency reference
- USB-C (single USB cable)
- 4 x SFP
- I2C or 1-Wire chip for serial number / ROM
- White Rabbit compatibility
The 7A50T-1CSG325C has 4 x GTP lanes, capable of 3.75 Gbaud. The primary use-case involves attaching one of those to a Marble over fiber.
The two MGTREFCLK signals are the direct White-Rabbit 125 MHz TCVCXO and the configurable MS5351M output.
- Standardized board size for good case options: Mini-ATX (150 x 150 mm)? Pico-ATX?
- 48 pins for 6 x Pmod
- 49 pins for DDR3 (equivalent to Arty and Marble-Mini)
- 13 pins for RGMII (including reset pin)
- 2 Ethernet PHY MDIO
- 4 pins for White Rabbit DAC (can attach LEDs to 2 x SYNC pins?)
- 1 or more clock input (not counting MGTREFCLK)
- 2 pins for I2C
- 14 pins for Arduino digital IO
- 8 pins for Arduino 4 analog channels
- 2 pins USB UART
- 3 pins SPI flash boot (not counting CCLK in bank 0)
total 146 so far, out of 150 possible with 7A50T-1CSG325C