P_Ch3 Questions and answers	P_Ch3

Consider the discussions in this page as an addendum to your PLA assignments. This edited Q&A come from meet sessions, emails, phone calls, and class and office time with many students. Thus they have significant value and will help you to save study time. You may imagine a class-group working cooperatively in a weekly basis with the objective of solving our projects as better and faster as we can. 

• PLA9 on basic digital I/O pins

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• PLA10_11 FSM adaptations, interrupts, LCD, TMR, etc.

Question: There is one thing I don't understand about the 7-segment digit sequencer: how the ST button works. When it is pressed does it send a single pulse and then the machine will work as long as it is not pressed again?

Answer: Well, for example, when an ST click is detected (external interrupt), the system generates continuously the sequence (start). When the button ST is clicked again it stops sequencing when the end of the sequence is reached. This feature is introduced at design step #3 at D3.6.

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Question: We have a question regarding the final PLA11. Because the project has three phases, how should we organize them? Do we have to deliver three separate reports, one for each of them? We don't have phase one done because neither me nor my team mate had this assignment for the last week, so we would also have to do it. If that's the case, could we do it incrementally, not repeating the information included in the other two reports? For example, if reading and writing ports is already included in the phase 1 report, not adding the same information on phases 2 and 3.

Answer: As shown in PLA11 page, this is a group project, unless you indicate otherwise to your instructor. Your team have to choose one of the two or three PLA10 that you solved individually and upgrade it firstly to design phase #2 and secondly to design phase #3.  These projects cannot be solved concurrently at the same time, they are successive upgrades adding new features at a time, step by step. In the same way that we invented P10 and PLA10 using the strategy of three design steps, for instance, step #1: rotate only clockwise with inhibit; step #2: make it reversible; step #3: add start/stop button.

And, respecting the report and video, the only thing that you have to go writing and explaining is what is different in every design phase from the base design in PLA10. How this mechanism of adding new features works and why we design complex projects in this particular way. Thus, first of all, we will check and correct whether you have completed 1-2-3-4 all the steps in PLA10; secondly, we will check and correct if you have completed 1-2-3-4 of the design phase #2 involving the LCD, and the same for design phase #3 respecting the use of TMR2.

As usual, only one zipped  project directory, only one group report (including annexes if you find it necessary) and only one 10 min. max video recording have to be submitted at Atenea before the due date.

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Question: I am working on the PLA11 project and I have a problem with the code to write on the LCD screen. It turns out that once I have written the code and I have introduced it in PROTEUS nothing is written on the LCD screen and I think it is because it is not well connected because when I start the simulation none of the lights turn on but I don't know how to fix it.

Answer: You should be working PLA11 in group with your team mate, so these questions should be asked by both of you and have to be of interest to both of you. Here there is nothing to fix, because the idea to begin with PLA11 is simply start writing "Hello World" in the LCD. This is your initial goal. And you know our way to do it when we start [3. Developing & 4. Testing] for any project:

1) Copy P11 or LAB11 project into the new location, and rename them.

2) Run and test that it works (as P11 or LAB11). Study the hardware and the software of such tutorial projects.

3) Complete all the design steps in your PLA10 design phase #1.

4) Study what hardware you have to add to your PLA10 design phase #1  so it looks like our LAB11 or P11 and becomes your PLA11 (design phase #2)

5) Study what software you have to add to your PLA11 (design phase #2) so you can simply print "Hello World"

6) ... etc. with only one step at a time (very few new code lines at a time) and run and test using both, step-mode and real time watching how variables of interest are evolving.

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Question: About calculate TMR2 parametres, we don't know which parameters are required to generate a CLK of 1kHz. Can you give me some advice please?

Answer: Yes, you can study the examples in P12 and LAB11. They are solved for both, TMR0 and TMR2, and the next day in class you can also ask questions on the matter. Please, ask questions in group. PLA11 is a group project. Remember that questions will be answered only if you attach diagrams, schematics, etc. as always from P1, and only in in step-by -step mode for 1-2-3-4 organization. You can only start phase #3 if phase #1 and phase #2 are completed and running and reported.

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Question: We have already done step 1 of phase #2 (LCD) and we are now facing step 2, trying to display dynamic data on our LCD. The problem is that the LCD pin named RW (read write) changes its signal between high and low when it is supposed to be only low for writing on the display screen. This issue causes problems in the data pins, causing logic contentions. We have not modified any library.

Answer: I cannot answer PLA11 questions if you are not asking in group. Are you monitoring R/W pin? I had no need to do it. What is your schematic? What is your code flowchart? Why are not you simply adapting any of our example tutorials? What are your new RAM variables now when you try to represent numbers? Study for example how it is done in P9 Adder_BCD_1digit_LCD. Besides, if you are solving step #2, it means that all your diagrams, schematics, pictures and report of step #1 has to be completed, and your hardware is running and so no need to modify it. You simply have to add and modify something in your flowchart, where, how? Ask further questions or show us your materials in next class.

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Question: Hem de fer a "specifications" el diagram de temps indicant totes les entrades i sortides?

Answer: If we don't go wrong, in PLA10 , in phase #1, you already drawn the application timing diagram. It is up to you to decide whether design phase #2 and phase #3 included in PLA11 implies modifications on timing diagrams or any other resource or flowchart.

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