How to write a design into a NeTV2’s flash

You want a bitstream written to a NeTV2’s SPI flash, so that it survives a power cycle.

The write replaces the bitstream in the NeTV2’s own SPI flash. Step 3 first copies that bitstream region into backup.bin on the Pi, and you copy it to your own machine. This page is for someone setting up or looking after a NeTV2; a visitor to a site’s board page never writes the flash. Loading into SRAM only is on the Raspberry Pi 3B+ page and the Raspberry Pi 5 page.

This procedure is waiting for its run: test-designs issue #249.

What you need

  • A NeTV2 wired as on NeTV2 wiring to a Raspberry Pi, with openFPGALoader on the Pi. The pins are 27:22:4:17, in the order TDI:TDO:TCK:TMS.

  • The cable for your Pi: -c rp1pio on a Raspberry Pi 5, from the openfpgaloader-fpgasonline-git package; --cable libgpiod on a Raspberry Pi 3B+.

  • The FPGA’s part and the size of its bitstream region in bytes. An XC7A35T board is xc7a35tfgg484 and 2228224; an XC7A100T board is xc7a100tfgg484 and 3866624.

  • Which of the two your board is: its JTAG scan reads 0x0362d093 on an XC7A35T and 0x03631093 on an XC7A100T (FPGA device variants).

  • A bitstream, here design.bit, no larger than the region.

Steps

  1. On a Raspberry Pi 5, run lspci -D -s 0001:01:00.0, the Pi 5’s PCIe slot. A line there is an endpoint to detach; no line, go to step 3.

  2. On a Raspberry Pi 5, detach it with echo 1 | sudo tee /sys/bus/pci/devices/0001:01:00.0/remove. Run lspci -D -s 0001:01:00.0 again: it prints nothing. If it still prints the line, stop.

  3. On the Pi, keep a copy of the bitstream region. Put your cable, part and size in place of CABLE, PART and SIZE. ls -l backup.bin shows SIZE bytes. Copy backup.bin to your own machine: a netbooted Pi loses it at its next reboot.

    $ sudo openFPGALoader CABLE --pins 27:22:4:17 --fpga-part PART --dump-flash --file-size SIZE backup.bin

  4. On a Raspberry Pi 5, run lspci -D -s 0001:01:00.0 again. If it prints a line, the endpoint came back after step 3: repeat step 2.

  5. On the Pi, write the bitstream to the flash and read it back. Without --fpga-part, openFPGALoader writes nothing.

    $ sudo openFPGALoader CABLE --pins 27:22:4:17 --fpga-part PART --write-flash --verify design.bit

To put the old bitstream back, run step 4, then step 5 with backup.bin in place of design.bit.

Check

Step 5 prints no line with failed and no Can't program SPI flash. Read the output rather than the exit status: some openFPGALoader builds exit 0 after a failed write. That the FPGA then starts the design from flash at power-up waits for this page’s run (test-designs issue #249).

If it fails

What you see

Likely cause

Fix

The Pi crashes or drops off during the write

On a Raspberry Pi 5, the PCIe endpoint was still enumerated

Detach it as in steps 1 and 2, then write again

Can't program SPI flash: missing device-package information

the command had no --fpga-part

run it again with the part from What you need

Verification failed at an address

the flash does not hold what was written

write again; if it fails again, write backup.bin back

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