LED blinker

Introduction

For my experiments with the Red Pitaya, I’d like to have the following development environment:

• recent version of the Vivado Design Suite
• recent version of the Linux kernel from Xilinx
• recent version of the Debian distribution on the development machine
• recent version of the Debian distribution on the Red Pitaya
• basic project with all the Red Pitaya peripherals connected
• mostly command-line tools
• shallow directory structure

Here is how I set it all up.

Pre-requirements

My development machine has the following installed:

• Debian 8.9 (amd64)

• Vivado Design Suite 2016.4 with full SDK

The installation of the development machine is described at this link.

Here are the commands to install all the other required packages:

sudo apt-get update

sudo apt-get --no-install-recommends install \
  build-essential git curl ca-certificates sudo \
  libxrender1 libxtst6 libxi6 lib32ncurses5 \
  bc u-boot-tools device-tree-compiler libncurses5-dev \
  libssl-dev qemu-user-static binfmt-support zip \
  squashfs-tools dosfstools parted debootstrap zerofree

sudo ln -s make /usr/bin/gmake

Source code

The source code is available at

https://github.com/pavel-demin/red-pitaya-notes

This repository contains the following components:

• Makefile that builds everything (almost)
• cfg directory with constraints and board definition files
• cores directory with IP cores written in Verilog
• projects directory with Vivado projects written in Tcl
• scripts directory with
  • Tcl scripts for Vivado and SDK
  • shell scripts that build a bootable SD card and SD card image

More details about the directory structure and about the toolchain can be found in the slides of my presentation at Club Vivado 2016.

Syntactic sugar for IP cores

The projects/led_blinker directory contains one Tcl file block_design.tcl that instantiates, configures and interconnects all the needed IP cores.

By default, the IP core instantiation and configuration commands are quite verbose:

create_bd_cell -type ip -vlnv xilinx.com:ip:processing_system7:5.5 ps_0

set_property CONFIG.PCW_IMPORT_BOARD_PRESET cfg/red_pitaya.xml [get_bd_cells ps_0]

connect_bd_net [get_bd_pins ps_0/FCLK_CLK0] [get_bd_pins ps_0/M_AXI_GP0_ACLK]

With the Tcl’s flexibility, it’s easy to define a less verbose command that looks similar to the module instantiation in Verilog:

cell xilinx.com:ip:processing_system7:5.5 ps_0 {
  PCW_IMPORT_BOARD_PRESET cfg/red_pitaya.xml
} {
  M_AXI_GP0_ACLK ps_0/FCLK_CLK0
}

The cell command is defined in the scripts/project.tcl script as follows:

proc cell {cell_vlnv cell_name {cell_props {}} {cell_ports {}}} {
  set cell [create_bd_cell -type ip -vlnv $cell_vlnv $cell_name]
  set prop_list {}
  foreach {prop_name prop_value} [uplevel 1 [list subst $cell_props]] {
    lappend prop_list CONFIG.$prop_name $prop_value
  }
  if {[llength $prop_list] > 1} {
    set_property -dict $prop_list $cell
  }
  foreach {local_name remote_name} [uplevel 1 [list subst $cell_ports]] {
    set local_port [get_bd_pins $cell_name/$local_name]
    set remote_port [get_bd_pins $remote_name]
    if {[llength $local_port] == 1 && [llength $remote_port] == 1} {
      connect_bd_net $local_port $remote_port
      continue
    }
    set local_port [get_bd_intf_pins $cell_name/$local_name]
    set remote_port [get_bd_intf_pins $remote_name]
    if {[llength $local_port] == 1 && [llength $remote_port] == 1} {
      connect_bd_intf_net $local_port $remote_port
      continue
    }
    error "** ERROR: can't connect $cell_name/$local_name and $remote_name"
  }
}

Getting started

Setting up the Vivado environment:

source /opt/Xilinx/Vivado/2016.4/settings64.sh

Cloning the source code repository:

git clone https://github.com/pavel-demin/red-pitaya-notes
cd red-pitaya-notes

Building boot.bin, devicetree.dtb and uImage:

make NAME=led_blinker all

Building a bootable SD card:

sudo sh scripts/debian.sh /dev/mmcblk0

SD card image

Building a bootable SD card image:

sudo sh scripts/image.sh scripts/debian.sh red-pitaya-debian-8.9-armhf.img 1024

The SD card image size is 1 GB, so it should fit on any SD card starting from 2 GB.

To write the image to a SD card, the dd command-line utility can be used on GNU/Linux and Mac OS X or Win32 Disk Imager can be used on MS Windows.

The default password for the root account is changeme.

A pre-built SD card image can be downloaded from this link.

Resizing SD card partitions on running Red Pitaya:

# delete second partition
echo -e "d\n2\nw" | fdisk /dev/mmcblk0
# recreate partition
parted -s /dev/mmcblk0 mkpart primary ext4 16MB 100%
# resize partition
resize2fs /dev/mmcblk0p2

Reprogramming FPGA

It’s possible to reprogram the FPGA by loading the bitstream file into /dev/xdevcfg:

cat led_blinker.bit > /dev/xdevcfg