ROACH FPGA Interfaces

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2x 40 differential pair connectors for ADCs, DACs, etc.


4x 10Gbps network connector for asynchronous high-speed communication.

These are the four rectangular connectors on a bulky metal riser on the back of the board. They are numbered from 0-3, starting on the bottom-right and proceeding counter-clockwise.

  • For communication via a switch or with a computer, use the 10GbE block.
  • For board-to-board communication, use either the 10GbE or XAUI block.


1x 40 differential pair connector for direct board-to-board communication.


16x general purpose input/output for low-speed control/status bits.

These are split between two 20 pin headers: J9 (aka GPIO A) and J2 (aka GPIO B). Each header has 8 GPIO pins, a +3.3V pin, and 11 grounds.

  • The data pins are labeled 0-7 on the board.
  • The +3.3V pin is above data pin 0.
  • The ground pin is below data pin 7.
  • All pins on the other half are grounded.

Each header has one direction selector that controls the direction of all 8 pins. For more information, see the GPIO block documentation.

For cabling convenience, two of the GPIO pins are also wired to SMA connectors. Pins 6 and 7 of GPIO A are wired to J11 and J10, respectively.

The GPIO inputs take 0-3.3V, ranging from DC to ~10MHz.


2x aux_clk SMAs for auxiliary clock inputs.

These are the two SMA headers next to the Z-DOK+ connectors: J12 and J13. These correspond to aux0_clk and aux1_clk, respectively. These are buffered through a high-speed comparator, making them ideal clock inputs.

The comparators are rated for up to 500MHz. The inputs are clamped to 0-5V and are DC coupled. If AC coupling is needed, remove R111 (and the input signal will then roll off below ~10MHz).

The aux_clk inputs take 0-5V, ranging from DC to 500MHz.

They are accessible as FPGA clock inputs from the XSG Core Config block.

2x GPIO SMAs for low-speed digital I/O.

These are the two SMA headers next to the CX-4 connectors: J11 and J10. These are wired to GPIO A data pins 6 and 7, respectively. Unlike the other GPIO pins, these are 50 ohm terminated.

The GPIO SMA inputs take 0-3.3V, ranging from DC to ~10MHz.

For more information, see the GPIO section above.

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