SSI Software Testing Tool
A railway signalling company that develops Solid State Interlocking (SSI) systems and the software that controls them was keen to automate the manual SSI software testing process to improve efficiency. The formal safety critical procedures that have to be adhered to within the railway signalling industry virtually prohibits the full automation of the SSI software testing process. Therefore, a software tool was developed to assist the SSI software testers by automating a substantial amount of the manual testing, without compromising the safety critical regulations.
The development of the software tool required extensive research to achieve a full understanding of the complex SSI communication protocol; the tool was required to interact with the busy communication stream in Real-Time, which required the development of a robust series of low level Interrupt software routines to manage the receipt and forwarding of SSI messages in a timely manner.
The software tool that was developed, 'listens' to the communications between the SSI Panel Processor Module (PPM) and the SSI Design Workstation (DWS) and decrypts the unique communication stream to enable the embedded messages to be displayed on a computer screen. In addition, the software tool enables these messages to be 'recorded' into 'script' files so that they can be 'played back' at a later stage in the testing process.
The test tool was the first of its kind to be developed and was a great success. It is now used internationally within the railway signalling industry and substantially reduces the time and effort required to validate Solid State Interlocking control software, resulting in a considerable reduction of testing costs.