The problems with this breathalyzer software are so evident, even the non-geeks here should be able to appreciate it. A few choice examples:

2. Readings are Not Averaged Correctly: When the software takes a series of readings, it first averages the first two readings. Then, it averages the third reading with the average just computed. Then the fourth reading is averaged with the new average, and so on. There is no comment or note detailing a reason for this calculation, which would cause the first reading to have more weight than successive readings. Nonetheless, the comments say that the values should be averaged, and they are not.

4. Catastrophic Error Detection Is Disabled: An interrupt that detects that the microprocessor is trying to execute an illegal instruction is disabled, meaning that the Alcotest software could appear to run correctly while executing wild branches or invalid code for a period of time. Other interrupts ignored are the Computer Operating Property (a watchdog timer), and the Software Interrupt.

6. Diagnostics Adjust/Substitute Data Readings: The diagnostic routines for the Analog to Digital (A/D) Converters will substitute arbitrary, favorable readings for the measured device if the measurement is out of range, either too high or too low. The values will be forced to a high or low limit, respectively. This error condition is suppressed unless it occurs frequently enough.

12. Defects In Three Out Of Five Lines Of Code: A universal tool in the open-source community, called Lint, was used to analyze the source code written in C. This program uncovers a range of problems from minor to serious problems that can halt or cripple the program operation. This Lint program has been used for many years. It uncovered that there are 3 error lines for every 5 lines of source code in C.

Posted by: Alice H at 10:36 PM | No Comments | Add Comment
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