Zybo Z7-10

This is the base Nerves System configuration for the Zybo Z7-10.

Feature	Description
CPU	667 MHz dual-core Cortex-A9 (ARMv7)
Memory	1 GB DRAM
Storage	MicroSD
Linux kernel	5.15
IEx terminal	HDMI and USB keyboard (can be changed to UART)
GPIO, I2C	Yes - Elixir Circuits
ADC	No, in this project's Bitstream
PWM	No, in this project's Bitstream
UART	1 available - ttyPS0
Display	HDMI
Camera	No, in this project's Bitstream
Ethernet	Yes
WiFi	No
Bluetooth	No
Audio	Yes

Using

The most common way of using this Nerves System is create a project with mix nerves.new and to export MIX_TARGET=zybo_z7_10. See the Getting started guide for more information.

If you need custom modifications to this system for your device, clone this repository and update as described in Making custom systems.

Linux's preempt_rt patches

If you need better real-time performance from the Linux kernel, the preempt_rt patch set may help. Be aware that we do not test with the patches so this may not work. To enable it, make a custom system using this one as a base and add the following to the nerves_defconfig:

BR2_LINUX_KERNEL_PATCH="http://cdn.kernel.org/pub/linux/kernel/projects/rt/4.19/patch-4.19.25-rt16.patch.xz"

Please verify the patch version since these instructions may be out-of-date.

Next, update the Linux configuration to use it. Review the Nerves documentation for running make linux-menuconfig and enable PREEMPT_RT_FULL. Alternately, make the following change to the Linux configuration:

-CONFIG_PREEMPT=y
+CONFIG_PREEMPT_RT_FULL=y

Build the system and you should now have a preempt_rt kernel.

Provisioning devices

This system supports storing provisioning information in a small key-value store outside of any filesystem. Provisioning is an optional step and reasonable defaults are provided if this is missing.

Provisioning information can be queried using the Nerves.Runtime KV store's Nerves.Runtime.KV.get/1 function.

Keys used by this system are:

Key	Example Value	Description
nerves_serial_number	"12345678"	By default, this string is used to create unique hostnames and Erlang node names.

The normal procedure would be to set these keys once in manufacturing or before deployment and then leave them alone.

For example, to provision a serial number on a running device, run the following and reboot:

iex> cmd("fw_setenv nerves_serial_number 12345678")

This system supports setting the serial number offline. To do this, set the NERVES_SERIAL_NUMBER environment variable when burning the firmware. If you're programming MicroSD cards using fwup, the commandline is:

sudo NERVES_SERIAL_NUMBER=12345678 fwup path_to_firmware.fw

Serial numbers are stored on the MicroSD card so if the MicroSD card is replaced, the serial number will need to be reprogrammed. The numbers are stored in a U-boot environment block. This is a special region that is separate from the application partition so reformatting the application partition will not lose the serial number or any other data stored in this block.

Additional key value pairs can be provisioned by overriding the default provisioning.conf file location by setting the environment variable NERVES_PROVISIONING=/path/to/provisioning.conf. The default provisioning.conf will set the nerves_serial_number, if you override the location to this file, you will be responsible for setting this yourself.

About board/system.bit, system.dtb, zynq_fsbl.elf

system.dtb

We use system.dtb which is generated by Zybo-Z7-10-Petalinux-2022-1.bsp.

system.bit and zynq_fsbl.elf

We regenerate Bitstream and FSBL by following steps to fix PS's GPIO

# refs. https://github.com/Digilent/digilent-vivado-scripts
git clone --recurse-submodules https://github.com/Digilent/Zybo-Z7.git
cd Zybo-Z7/
git checkout 10/Petalinux/2022.1-1
git submodule update --init --recursive

1. Start Vivado 2023.2
2. Click Tools -> Run Tcl Script...
3. Select Zybo-Z7/hw/scripts/checkout.tcl and click OK
4. Fix MIO 50 and 51 pullup, from enable to disable
5. Generate Bitstream
   Critical warnings related to dvi2rgb occurs,
   but it only affects HDMI-in and has no effect on anything else, so we ignore them.
6. Export XSA
7. Create platform for the XSA
8. Build FSBL

Overwriting Files in the Boot Partition

see. Nerves Advanced Configuration

About UIO

• LD0-3 are binded with /dev/uio0
• SW0-3 are binded with /dev/uio1's GPIO
• BTN0-3 are binded with /dev/uio1's GPIO2
• LD6 is binded with /dev/uio4

see. UIOSAMPLE.md

Loading Bitstream and dtbo at Linux runtime

1. upload Bitstream and dtbo to /tmp by sftp
2. invoke following,

iex> cmd "cp /tmp/your_bitstream.bit.bit /lib/firmware"
iex> cmd "mkdir /configfs/device-tree/overlays/your_overlay"
iex> cmd "cat /tmp/your_overlay.dtbo > /configfs/device-tree/overlays/your_overlay/dtbo"