The board is powered from a standard 5 V ± 5% (4.75 V to 5.25 V).
This power supply is used by:
- the Raspberry Pi which generates a 3.3 V for itself and for the FPGA I/O banks
- a DC/DC converter which generates a 1.5 V for the FPGA core
The FPGA is supplied with:
|GNDQ||quiet ground||0 V|
|VCOMPLA/B/C/D/E/F||PLL ground||0 V|
|VCC||core supply||1.5 V|
|VCCIBx||I/O supply||3.3 V|
|VMVx||quiet I/O supply||3.3 V|
|VCCPLA/B/C/D/E/F||PLL supply||1.5 V|
|VJTAG||JTAG supply||3.3 V|
|VPUMP||programming supply||3.3 V|
Board to board
The inter-board connection is a serial bus with differential Tx and Rx lines. These channels are duplified for reasons of security. To this comes a 0 V and 5 V power supply.
The connection is done by a 4-pin connector on each corner of the board. Each corner transmits 0 V, 5 V and a differential pair.
Raspberry Pi to FPGA
All Raspberry Pi I/O lines are connected to the FPGA. xxx of them are connected to the FPGA programming lines.
The Raspberry Pi Zero loads its operating system from the SD card.
The FPGA can be programmed either from the JTAG connector or from the Raspberry Pi. One has to make sure that the lines on the Raspberry Pi connector are tri-stated when trying to program the FPGA.