Board to board
The inter-board connection is a serial bus with coaxial cables for Tx and Rx lines. These channels are duplified for reasons of security. To this comes a 0 V, a 3.3 V and 5 V power supply.
The connection is done by coaxial connectors on two board sides.
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.
The board is powered from a standard 5 V ± 5% (4.75 V to 5.25 V) as defined for USB. An additional 5 V can be supplied too.
This power supply is used by:
- the Raspberry Pi which generates a 3.3 V for itself
- a DC/DC converter which generates a 1.5 V for the FPGA core from the 5 V power supply
The RPi 3.3 V can be used for the FPGA I/O banks through a 0 Ω resistor if there is no 3.3 V power from the inter-board connector.
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|