Release builds of HPS firmware are incapable of capturing or transferring image data by design.
However it can be useful for development and testing purposes to “see what HPS sees”. The image-transfer Cargo feature (disabled by default, and disallowed in signed firmware) adds some extra code to the FPGA application which captures and transfers image data over I2C to the host.
If you are using HPS proto2 (see Working with proto2), the monitor program can receive and save images captured by the FPGA.
As a convenience, you can use the scripts/fpga-rom-run wrapper script, which first takes care of building the FPGA application with development features enabled, and then tells the monitor to update SPI flash and launch the FPGA application.
Pass the --image-out option to specify an absolute directory where images should be saved. You can also use the --cmd option to enable image transfer immediately after the FPGA application is launched:
scripts/fpga-rom-run --image-out $(pwd)/images/ --cmd 'transfer 1'
Example output:
Running `target/debug/hps-mon --openocd-port 4444 --gateware /mnt/host/source/src/platform/hps-firmware2/build/hps_platform/gateware/hps_platform.bit --soc-rom /mnt/host/source/src/platform/hps-firmware2/build/hps_platform/fpga_rom.bin --test-data-dir /mnt/host/source/src/platform/hps-firmware2/test_data --cmd 'reset_mcu; write_gateware; write_soc_rom; launch_app_without_i2c' --image-out /home/dcallagh/chromiumos/src/platform/hps-firmware2/images/ --cmd 'transfer 1'` Welcome to hps-mon. Press enter to activate console. CRC checked 7 of 7 blocks All blocks already up-to-date. Nothing to write. MCU> INFO: Found expected flash chip MCU> INFO: Default HM01B0 configuration applied MCU> INFO: MCU application started. CPU is running at 60MHz CRC checked 10 of 14 blocks CRC checked 14 of 14 blocks All blocks already up-to-date. Nothing to write. MCU> INFO: FPGA reported boot #1 FPGA> Hello from the Rust FPGA FPGA> Classifier status: InitOk FPGA> Image transfer: true Wrote "/home/dcallagh/chromiumos/src/platform/hps-firmware2/images/00000000.raw" Wrote "/home/dcallagh/chromiumos/src/platform/hps-firmware2/images/00000000.png" Wrote "/home/dcallagh/chromiumos/src/platform/hps-firmware2/images/00000001.raw" Wrote "/home/dcallagh/chromiumos/src/platform/hps-firmware2/images/00000001.png" Wrote "/home/dcallagh/chromiumos/src/platform/hps-firmware2/images/00000002.raw" Wrote "/home/dcallagh/chromiumos/src/platform/hps-firmware2/images/00000002.png"
The hps-factory capture-images command can capture images. This requires that WP is deasserted. Signed release firmware is incapable of capturing images, and the unsigned development firmware embedded in hps-factory will fail to start on a ChromeOS DUT with WP asserted.