Student "edition" found at {csi dot journalspace dot com}.

Maybe I shouldn't have started this blog now, not with everything that's been going on.

For the three hour meeting of my Interfacing Computer Systems class for the twelfth week of the second term, we just continued with their probably last experiment, with the external circuit being interfaced to the parallel port of the computer.

The students still pushed through with their intent to learn all about each aspect of the experiment and not concentrate on just one aspect such as the hardware or the software, since they already know (and it is only justified) that in the exam they will be asked about both sides of the interfacing.

This time, they could test both the circuit and the program independently before connecting them. In fact, one group did that, testing the possible four bit inputs and outputs first to see if the circuit already worked.

I did not trouble shoot anymore one student of one group who said that their program (or specifically the command) for writing to the parallel port would not work.

This is because the only way they were able to reach that experiment is if they had made all the previous experiments work, which are all aspects of the current experiment that they have already finished independently.

It turned out though, that the student had overwritten one of the previous programs in the computer they were using the lab, which contained the correct and functional code. When he edited the file, he had removed one of the declarations for the outgoing function, which was why it was generating an error when he was compiling it, because the definition of the command could not be found.

Another group had difficulty sending out the two four-bit numbers out to the external circuit. This is because they were passing them off consecutively instead of simultaneously.

They seemed to be ignoring the fact that they could hand through eight bits of data at the same time, so all they and to do was to put one of the fifteen-maximum-value numbers in the high four bits of the outgoing byte, and let the external circuit read them all at once. They just needed to multiply the first number by sixteen and add it to the second number before putting in the parallel port data address.

Maybe next time I will make them subtract a three bit number from a five bit number instead. But then, the answer must be able to fit in four bits it to be sent back to the computer by the external circuit.

I’ll have to polish the instructions on this a bit more if I’m going to assign it to them, or to the next class to take up this subject that I will teach.

Session 875 also erased the old program. Class dismissed.