Flash the SD-Card
Both GenesysII boards and Nexys4-DDR boards support an SD-Card for mass storage. GenesysII boards require the card to be inserted with the writing upwards, Nexys4-DDR boards require the card to be inserted with the pins facing upwards.
SD-Card makes and models differ considerably in performance. Sandisk Ultra cards perform adequately but rather slowly, Samsung PRO Endurance cards perform best and fastest. This is most noticable when plugged into a host adaptor, but also affects performance in a lesser way on the FPGA board. It is unrealistic to expect that the FPGA can approach the speed of a host-based adapter, because:
- It does not have DMA implemented
- It does not have DDR or voltage switching
- Many of the advanced SD-Card specification details are secret. Linux treats it as an MMC card with small deviations.
It is possible to boot Linux without any SD-Card in place, however this functionality requires a ram-disk to be initialised from QSPI memory. This memory is rather small and requires a high degree of compression to achieve a minimum environment (busybox+network+disk tools). Consequently decompression on each boot is rather slow. A more flexible experience is available if the Linux kernel is stored in the first (DOS format) partition of the SD-Card. This is the mode of installation that is assumed by the following procedure.
Identifying your SD-Card in the host adaptor
Type lsblk before and after inserting the SD-card and its adaptor into the computer. You should see new devices added, similar to the following:
sdc 8:32 1 14.9G 0 disk
├─sdc1 8:33 1 32M 0 part /media/jrrk2/2BBB-DCFE
├─sdc2 8:34 1 2G 0 part /media/jrrk2/c7370d8e-67dd-405f-abe5-0a6d40fef98d
├─sdc3 8:35 1 512M 0 part
└─sdc4 8:36 1 12.3G 0 part /media/jrrk2/578a1c8d-92c9-48cb-9fdc-c593d5c68107
Ubuntu by default will automatically mount any readable partitions on the card. These partition(s) need to be unmounted and removed to install the operating system. This happens as one of the automatic steps within the Makefile.
READ THIS WARNING (!)
The procedure below erases all data on the disk, so do not mistakenly specify your hard drive or external mass storage. Some checks will be carried out, such as skipping UUIDs found in /etc/fstab. The instructions below refer to sdc. If your USB disk shows up as something other than sdc, you need to run the following commands with the parameter
USB=whatever, where whatever is whatever your removable disk is called
instead of
USB=sdc
IF YOU DO NOT UNDERSTAND THIS, DO NOT PROCEED, GET SOME HELP !!!
If you use a fresh card, only sdc1 will typically be present. If you use the recommended operating system Ubuntu 16.04.5⁄18.04.4 LTS, any known partitions will be mounted and automatically shown in individual windows, unless you have changed the defaults. Regardless of this, do
make sdcard-install USB=sdc
and watch out for any device busy messages.
Remote serial console (only) bitstream installation
For remote serial console installation without any of the VGA or HID functions, the USB master function of the FPGA board is not needed and may be used to interface to a USB memory stick containing the required bitstream. Vivado is not needed which is an advantage since it is a multi-gigabyte download. You can use the following command (all the same caveats about being very careful to choose the correct disk apply as above). There is no particular reason why the USB memory stick will come up with the same drive letter as the SD-Card, so this needs to be rechecked with the lsblk command.
make memstick USB=sdc
To use this method JP1 must be in the USB/SD position and JP2 should be in the USB position. Once configured, the USB stick is inaccessible to Linux and cannot be used to store other files. After pressing the PROG button with the USB memory stick inserted the BUSY light should glow amber steadily for 30 seconds or so, then the green DONE light will come on. In the event of failure, the amber BUSY light will flash slowly, in this case it is worth trying a different memory stick.
Configuration from SD-Card is not supported in this release (because the onboard PIC places the SD-Card in 1-bit SPI mode, and we need it in 4-bit SD mode). If a method is found to return to 4-bit SD-mode, then this mode can be supported in a future release (ejecting the card and reinserting it might do it, but potentially will reduce its life also).
Continue the process below: