Custom Instrument - Signals Tab

This tab of the Custom Instrument Configuration dialog is divided into the following five regions.

Instrument Options

This region of the tab allows you to define some basic options for the Custom Instrument:

• Title – this is the caption used at the bottom-right of the instrument's panel, when accessed at run-time. This allows you to give the panel a meaningful name, which would typically reflect the role of the instrument.
   
  
  Figure 1. Customize the title for the instrument as required.

• Show Options Button – enable this option to include an button at the bottom-left of the instrument's panel. When present, it provides access to the Custom Instrument - Options dialog. Input values to, and output values from, the Custom Instrument, are refreshed (updated) in accordance with the value specified in the Update Display From Core Every field of this dialog. In other words, this is the defined polling interval. By default, the values will be refreshed every 250ms.

• Show Synchronize Button – enable this option to include a button at the bottom-left of the instrument's panel. When present, it provides the ability to manually refresh the IO values to/from the Custom Instrument – manual polling if you will.

• Use Custom Bitmap – use this option to determine the icon that will be used to represent the Custom Instrument, in the Soft Devices JTAG chain of the Devices view. With this option disabled, the Custom_Instrument.bmp image file will be used, which is located in the \Library\Device Images folder of the installation. To use your own, customized image, simply enable the option and click the Select Bitmap button. Use the subsequent dialog that appears to locate and open the required image file.
   

  When creating a customized bitmap it is important to keep in mind that the Devices view will only display an image that is 80x70 pixels in size. Larger than this and it will be cropped, smaller and it will be centered within these bounds accordingly.

   
  
  Figure 2. Customize the presentation of the instrument in the Devices view.

Interface

Use this region of the tab to define all IO for the instrument – the input signals to be monitored and output signals to be generated. Default signals are added in the form AIN[7..0], BIN[7..0], AOUT[7..0], BOUT[7..0], and so on. Click on, and edit, an entry as required. Give the signals meaningful names to reflect what is being monitored and/or controlled.

Use the controls available directly under a signal list to add (), remove () or re-order ( and ) signals as required. The latter allows you to change the order of the signals with respect to the instrument's schematic symbol.

For output signals, you can also set an initial value, using the associated Initial value (hex) field. By default this will be zero.

Figure 3. Example interface definition for a Custom Instrument.

Schematic

Depending on the naming used for input and output signals, the default width of the symbol used for the instrument on the schematic sheet may be too small, resulting in overlapping text. Use the Schematic Component Width option in this region of the tab, to resize the symbol in the horizontal plane as required. The value is entered as DXP Default units, where 1 DXP Default unit is equal to 10mils.

Figure 4. Resize the width of the instrument's symbol on the schematic to enhance readability.

Configuration File

This region of the tab is where the file, into which all configuration information will be stored, is specified. Storage of configuration information in a separate file (*.Instrument) allows for portability of customized instruments between projects and installations – why use someone else's instrument, when you can take your favorite with you!

If creating a new configuration for the instrument, simply click on the folder icon, at the far right of the Configuration File Name field, and use the subsequent Save Configuration File To dialog to nominate where, and under what name, the file is to be saved. Typically, you would save the file to the same location as the parent FPGA project.
 

 
If you wish to configure the instrument using information stored in an existing configuration file, simply click on the Load From Existing button and use the subsequent Choose Instrument File dialog to browse to, and open, the required file. The information stored in the file will be loaded, where applicable, into each of the three tabs of the Custom Instrument Configuration dialog.

Note: It is possible to have multiple Custom Instrument components in the same design, all sharing a single .Instrument file. The configuration would be defined for one and the resulting configuration file loaded by all others. Editing one will therefore affect all.

Configuration Retrieval

This region of the tab is used to specify the method by which Altium Designer can access the relevant configuration information, for a custom instrument that is detected in the Soft Devices JTAG chain:

• From Project – the configuration information is retrieved from the corresponding .Instrument file for the instrument, which resides in the location specified in the Configuration File Name field (described previously). The project must be open in order to show the instrument from the Devices view.

• From FPGA – the configuration information is downloaded with the design to the physical device, and stored in Block RAM. It is retrieved directly from here and the project need not be open.