Host Computer To SimPhonics Computer Interface

feature author: Paul Halliday

The Host Computer to SimPhonics computer interface for the Beech 1900D was implemented using SimPhonics’ Custom Socket I/O Driver. This driver is a UDP/IP socket interface that is customizable down to the bit level. Customization is done through a standard database format accessible through Open Database Connectivity (ODBC). The structure of the interface is defined using an ODBC-compatible database in the format described in SimPhonics’ Custom Socket I/O Driver User Manual. For the Beech 1900D simulator, we were given a Microsoft Access database written by SimPhonics. This database contains a table called HostBuffer, which essentially defines the data to be sent from our host to the SimPhonics computer. The HostBuffer table is mapped directly to the VPlusPorts table in a one-to-one entity relationship (we didn’t need to pack any bits to save space or bandwidth, but it can be done if necessary). The VPlusPorts table is then accessible in V+ as a list of input ports that are used in designs. A list of all of the host interface ports is obtained by clicking on the ports icon of the V+ Visual Programming System toolbar (see Figure 2). Throughout the rest of this article, these ports will be referred to as host inputs or input ports.

Figure 2.  Host-to-Audio Ports

Our host computer is a Concurrent PowerMax PC running a real-time UNIX operating system. We needed to establish a port number for the UDP/IP socket on both the host and SimPhonics computers. This is just an arbitrary number not used by any other socket interface on either system. Once both computers were configured and running, we found some discrepancies that were fixed in relatively short order. In some cases the fix required a change to the Access database which we did using Microsoft Access 2000. In most cases changes were made on the host side to rectify the problem.

When SimPhonics populated the database, every attempt was made on their part to make use of already existing data in the host models. It was then a simple matter of defining a packet on the host side that exactly matched the description of the HostBuffer table. This packet was then transmitted across the UDP/IP socket at a 60 Hz rate.

It should be noted here that this particular interface is only one-way: from the host to the SimPhonics computer. If needed, a two-way interface could be implemented.

Review the HostBuffer table