Unlike physical hardware, the equivalent logic circuitry embedded in an FPGA can’t be probed, tested and monitored in the conventional way. The logic hardware programmed into the device is simply inaccessible. Embedded designers traditionally rely on complex FPGA circuit simulation, and use up valuable FPGA pins to bring out key signal and data lines for monitoring purposes.

Altium Designer avoids these compromises by providing FPGA-based virtual instruments that carry out the typical functions found in bench-top test instruments. The hardware portion of the instrument is connected into the design at the schematic level and downloaded to the FPGA along with the circuit under development. The instrument is then controlled via JTAG using soft front panels available within the Altium Designer environment.

Altium has added a new dimension to the concept with the introduction of a fully-configurable Custom Instrument. You can now construct your own instrument to monitor and control signals within the FPGA. With the custom virtual instrument, you first choose the number and type of inputs and outputs you want, and create custom scripts (in DelphiScript) to process the signals or respond to events as required.

Monitor and process any FPGA signals

You can then build a custom interface or GUI for the instrument from a palette of standard components and instrument controls. This is the interface that’s seen once the design is programmed into the target device and instrument then accessed. The virtual front panel is fully customizable, including the instrument’s title, and you can use the various properties associated with the controls to customize it further.

The defined I/O signals can be directly hooked up to the controls on your custom GUI, or you can write a DelphiScript to process those I/O signals. This will occur when the instrument is polled and in response to specific events, providing a flexible system for processing I/O signals.

Also, an instrument you create is portable. The instrument configuration is stored in a separate file, so you can take your own customized instruments from one project or installation to another. When an FPGA design is processed and a custom instrument is detected on the Soft Devices JTAG chain, Altium Designer simply retrieves the associated configuration information.

Define the look, feel and operation of the instrument exactly how you want it

One notable feature of the custom instrument is that the interface can be stored as part of the design that is downloaded to the FPGA. This means that you can create full custom test or maintenance interfaces for a product and store it inside the design. In this case the configuration information is retrieved from the FPGA itself. Any service engineer can then plug in to the design using Altium Designer, and instantly have access to the custom instrument panel without needing a copy of the instrument definition stored on their computer.

To find out more about what you can do with Altium Designer check out the training videos at: How to Create Your Own Virtual Instrument