Station Interface Box
May 26, 1997
The purpose of this article is to describe an idea for a new type of interface between the typical modern ham-radio station and the host computer. This will present the reasons I see the need for such an interface, and a suggested block diagram level hardware and software implementation for it. Interfacing systems to computers is not a new topic and has been done by amateurs for a long time, but I believe that the ideas presented here could enhance the abilities of any ham-radio station.
What is the Station Interface Box ?
The station interface box is an interface between the computer and all of the accessories in a typical modern ham-radio station. Such an interface should include digital outputs, digital inputs, analog inputs, and serial communications ports.
The uniqueness of this interface is that is should have enough I/O to enable it to interface to a complete station, thus, it should have the flexibility to enable every ham to adapt it to his own station
Why do we need it ?
There are a couple of reasons we need the SIB:
How can we implement it ?
At first I tried to find the solution in commercial I/O cards, but found all of them to be too limited for this application or just too expensive. Due to this I realized that the interface will need to be defined and built specifically to meet the needs of the Ham-Radio community.
Looking at conventional interfacing techniques I realized that there are three options. The first is to build a slot type interface card, the second is to use a serial communications port, and the third is to build on the newly introduced USB. Evaluating the three options I came up with the following conclusions. A built in slot card has the advantages of being fast and simple because it interfaces to the computerís bus directly. The disadvantage of it is that it is not easy to experiment with, because of the fact that it is installed in the computer, and the relatively expensive fabrication costs of a PC slot type card. The serial port option is very conventional and has the advantage of being easy and safe to experiment with. The disadvantage is that the circuit is more complex due to the fact that RS232 has to be used in order to read and write information from the interface. Another disadvantage is that the serial interface has a rather slow data rate compared with a slot or USB. The good thing is that most modern computers can go up to 115200 baud which is sufficient for most I/O applications. The third option is the newly announced USB standard. Having read about the standard and visited there Web page I realized that this interface is ideal for such an application. It offers a very high data transfer rate and does not consume limited computer resources. The major disadvantage of the USB is that you have to pay a large sum of money in order to be allowed to develop applications for it. Another disadvantage is that the USB has not yet become a widely used interface, but it is a very appealing interface for future applications. Having evaluated the common interface options I came to the conclusion that the serial option is the best options under the current limitations.
Going along with the serial port implementation, a microcontroller needs to be introduced to manipulate the acquired information and transport it into the computer. A suggested block diagram is suggested in figure 1. As can be seen from the figure, the SIB will have a basic I/O configuration with no fancy gadgets. This simplicity will ensure the device has a large flexibility towards different I/O options. You will probably notice that the actual hardware ports are not defined. This was not yet determined because at this stage this is just a conceptual suggestion.
Next problem is the software interface to the box. Utilizing a single serial port to the S.I.B. would in normal cases limit the number of applications using it to one, because applications cannot share the port simultaneously. Having the SIB interface to numerous different device would mean that they might all want to talk to the SIB at once. This problem could be solved by a software interface very similar to the Winsock interface. Such an interface is described in figure 2. Such a socket will be the only application to talk to the serial port, while providing a standard interface for the applications that wish to access the SIB. This way the computer will be able to run several different applications each having the possibility to access the stationís hardware devices.
In this article I presented an idea of a new type of interface between a personal computer and the modern Ham-Radio station. The idea behind the interface is to provide greater flexibility in using the computer to control the modern Ham-Radio station. A block diagram level design has been suggested and an actual hardware/software level implementation has to be defined in the future.
I feel that the idea presente in this article fills a hole which exists in the modern Ham-Radio station and openís possibilities for future applications. At this stage we will have to see whether such a project would achieve the necessary support to bring it from a conceptual stage to a practical design stage.