fpgalafw

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This is a preliminary design

fpgalafw is a proposal for a project to implement a universal logic analyser firmware for use as a firmware for commercial logic analysers that we wish to support, on FPGA development boards and for use as an in-circuit, or even in-FPGA debugging tool.

Contents

Benefits

  • Would simplify the implementation of libsigrok.
    • Reduced repetition.
    • Advanced triggering becomes hard when every manufacturer has a different trigger model. We can implement one to cover a variety of devices.
  • Unlock previously unsupported device features. If a feature is added to one LA, it is added to all.
  • Would enable support for more analysers such as the RockyLogic Ant8, the RockyLogic Ant18e, the ChronoVu LA8 etc.

Goals

  • 100% open-source Verilog implementation (written from scratch or based off of other open-source projects).
  • Portable Verilog implementation that works (as much as possible) in a generic way.
    • Should work across all common FPGA/CPLD families from various vendors, including Xilinx, Altera, Microsemi/Actel, Lattice, etc.
    • Should work for any suitable FPGA/CPLD based logic analyzer board (existing devices or future ones than can be built specifically for use with this project), and any suitable CPLD/FPGA eval boards.
    • This means that the use of vendor-/family-specific constructs are discouraged in the "core" of the code. There might be optional per-device or per-vendor constructs that are not portable, but those should be moved outside the "core" so that as much functionality as possible works for any device.

Previous Projects

There are various pre-existing open source firmware projects that can be drawn upon:

Status

Some intitial work has been done, but the project is not really started yet. The current best branches are

Components

fpgalafw will not work as a monolithic single firmware. Rather it is a library/framework of components that can be assembled together depending on the capabilities of the device, and the mode of operation.

Host Interface
  • Cypress FX2
  • FTDI FT245 USB Fifo
  • RS232 (SUMP)
  • Ethernet
  • USB-MCU
  • JTAG - for ChipScope-like in-circuit use cases.
  • PCIe?
  • Parallel Port?
  • Cypress FX3?
Storage
  • Internal Block-RAM (BRAM)
  • External DRAM
  • External SDRAM (DDR2, DDR3)
  • Burst RAM
  • Internal Soft-RAM? (Shift Registers)
  • Streaming Pass-through
Data Packer
  • N-probes to M-data Lines Muxer
  • RLE Encoder
  • RLE + Golomb/Huffman/... Encoder?
Indicator LEDs
  • None
  • Tri-colour
  • Multiple LEDs
Operating Modes
  • Storage Sampling
    • Asynchronous Mode
    • Externally Clocked Synchronous (State Analysis) Mode
  • Continuous Sampling
  • Pulse Counter
  • Time-to-digital Conversion
  • Signal Generation
Triggering
  • External
  • Simple (Edge/Level)
  • Time Delayed
  • Advanced Triggers (the Demon Core replicates the behaviour of the HP16550)

Project Folder Structure

Proposed project folder structure...

  • /
    • README
    • NEWS
    • Makefile
    • /boards
      • /openbench-logic-sniffer
      • /nexys2
      • /papilio ...
    • /rtl
      • /verilog
        • /host-interface
          • /cypress-fx2
            • /software
            • /firmware
          • /sump
            • /firmware
            • ....
        • /storage
          • /ddr2
            • /firmware
          • /bram
            • /firmware
    • /tools
      • # Scripts etc in here
    • /sw
      • # Embedded sofware here

Firmware Packaging

Each device class will be given a firmware package that the driver can load. This package will be ZIP-file containing multiple firmware .bit files for the different permutations of modes and options that can be selected on this device. It is undesirable to have a single universal hardware file for each device, because multiple features will compete for use the limited number of logic units and internal storage.

The firmware package will contain a text index file that indicates the capabilities of the device, its Bus ID, and a list of the firmware files available.

Firmware Build Environment

The firmware will be built using a GNU Make driven build environment, which will be compatible with Altera, Xilinx, Microsemi/Actel, Lattice tools, and FreeHDL etc.

Protocol

We will implement a common command protocol, common among all the host interfaces. (With the possible exception of SUMP if we plan to support that).