The logictools overlay consists of programmable hardware blocks to connect to external digital logic circuits. Finite state machines, Boolean logic functions and digital patterns can be generated from Python. A programmable switch connects the inputs and outputs from the hardware blocks to external IO pins. The logictools overlay can also has a trace analyzer to capture data from the IO interface for analysis and debug.
Logictools base diagram¶
The logictools IP includes four main hardware blocks:
- Pattern Generator
- FSM Generator
- Boolean Generator
- Trace Analyzer
Each block is configured using a textual description specified in Python. No compilation of the configuration is required. This means a configuration can be loaded directly to the generator and run immediately.
PYNQ-Z2 logic tools¶
The PYNQ-Z2 logictools overlay has two instances of the logictools LCP (Logic Control Processor); one connected to the Arduino header, and the other connected to the RPi (Raspberry Pi) header.
The Arduino header has 20 pins, and the RPi has 26 pins that can be used as GPIO to the LCP.
The 4 LEDs, and 4 pushbuttons can also be connected to either LCP, extending the number of inputs available. Note that the LEDs and pushbuttons are shared, and can only be used by one LCP at a time.
The overlay also includes a Pmod IOP connected to PmodB. This is the same Pmod IOP that is used in the base overlay.
The Pattern Generator can be configured to generate and stream arbitrary digital patterns to the external IO pins. The Pattern Generator can be used as a stimulus to test or control an external circuit.
Finite State Machine (FSM) Generator¶
The FSM Generator can create a finite state machine from a Python description. The inputs and outputs and states of the FSM can be connected to external IO pins.
The Boolean Generator can create independent combinatorial Boolean logic functions. The external IO pins are used as inputs and outputs to the Boolean functions.
The Trace Analyzer can capture IO signals and stream the data to the PS DRAM for analysis in the Python environment. The Trace Analyzer can be used standalone to capture external IO signals, or used in combination with the other three logictools functions to monitor data to and from the other blocks. E.g. the trace analyzer can be used with the pattern generator to verify the data sent to the external pins, or with the FSM to check the input, output or states to verify or debug a design.
A PYNQ MicroBlaze is used to control all the generators and analyzers. The PYNQ MicroBlaze subsystem on logictools overlay also manages contiguous memory buffers, configures the clock frequency, and keeps track of the generator status. For more information, please see PYNQ Libraries.
The API for the logictools generators and trace analyzer can be found in PYNQ Libraries.
Rebuilding the Overlay¶
The process to rebuild the logictools overlay is similar to the base overlay.
All source code for the hardware blocks is provided. Each block can also be reused standalone in a custom overlay.
The source files for the logictools IP can be found in:
The project files for the logictools overlay can be found here:
To rebuild the overlay, source the Xilinx tools first. Then assuming PYNQ has been cloned:
cd <PYNQ Repository>/boards/Pynq-Z2/logictools make
To rebuild from the Vivado GUI, open Vivado. In the Vivado Tcl command line window, change to the correct directory, and source the Tcl files as indicated below.
Assuming PYNQ has been cloned:
cd <PYNQ Repository>/boards/Pynq-Z2/logictools source ./build_logictools_ip.tcl source ./logictools.tcl
To build from the command line, open the Vivado 2017.4 Tcl Shell, and run the following:
cd <PYNQ Repository>/boards/Pynq-Z2/logictools vivado -mode batch -source build_logictools_ip.tcl vivado -mode batch -source logictools.tcl
Note that you must change to the overlay directory, as the .tcl files has relative paths that will break if sourced from a different location.