代写ESE 123 Laboratory 9 Stopwatch and Timer代做R编程

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ESE 123

Laboratory 9

Stopwatch and Timer

Parts list:

Quantity	Reference	Value	Description
¼	D1	Red	Display, Four Digit LED, Red
¼	D1	Blue	Display, Four Digit LED, Blue
¼	D1	White	Display, Four Digit LED, White
¼	D1	Yellow	Display, Four Digit LED, Yellow
4	Q1-Q4		TRANS PNP 40V 0.2A TO92
3	SW1-SW3		SWITCH TACTILE SPST-NO 0.05A 12V

Objec/ves:

In this experiment we will:

• Install the 7 segment numeric display and associated drive circuitry

• Install the tacAle switches

• Learn some more coding

Displaying decimal numbers using integer division and modulo:

If we want to display a binary number in decimal we need to make a series of conversions. We ﬁrst need to convert the binary number to a decimal number, and then we need to look up which segments should be turned on to represent the number’s glyph (the LED segments are turned on to represent the number). The laMer conversion is handled by the display_digit funcAon.

If we have a four digit decimal number, say 6837, we can ﬁnd the ﬁrst decimal digit by integer dividing by 1000 to get 6 and displaying the 6 in the thousands digit (digit 1 on our four digit display). Assuming we had saved 6837 in an integer variable called disp_int, this would look like:

display_digit (disp_int/1000, 1);

We then use the modulo funcAon to ﬁnd the remainder − the hundreds, tens, and ones and save it in the original variable. ATer this operaAon disp_int would contain 837:

disp_int = disp_int % 1000;

Now we can repeat the process for the next digit. We integer divide by 100 to get the number of hundreds (8) and display this in digit 2:

display_digit (disp_int/100, 2);

And compute the remainder (37) − the hundreds are gone, the tens and ones remain:

disp_int = disp_int % 100;

The tens (3) are displayed next:

display_digit (disp_int/10, 3);

And then the ones (7):

display_digit (disp_int%10, 4);

Note that disp_int starts at 6837, but ends as 37. This display procedure destroys the original value. If we wanted to retain the original value, we would need to make a copy.

Procedure: circuit assembly

In today’s lab you add the four digit LED display, the remaining digit select transistors, and the pushbuMons. The LED display is available in red, blue, white, or yellow.

1. Collect the parts for today’s lab from your TAs.

2. Carefully clip oﬀ pracAce resistors R1 through R5 with wire cuMers. These are the resistors you ﬁrst learned to solder with. The LED display will be installed directly over this area and it will not lie ﬂat against the board if there are any large (>1 mm) protrusions in this area.

3. Install the four digit LED assembly. Note that there are six pins on one side of the device and seven pins on the other; the LED will ﬁt only one way around. The wire leads on this device are thin and ﬂexible, and this will make it diﬃcult to get all the leads into the circuit board at the same Ame. Force will not help the situaAon. What will help is:

3.1.Making certain that the pins are straight before you start.

3.2.Using a thin tool (tweezers or a Any screwdriver) to help guide the pins into the holes one at a Ame.

4. Ensure that the LED display is lying ﬂush against the board and solder one pin. Check to see that the LED is sAll ﬂush and then solder the remaining pins. The LED assembly has a plasAc ﬁlm protecAng it from damage. It is probably a good idea to leave this ﬁlm on the LED unAl we complete the case.

5. Install four 2N3906 pnp transistors at Q1 through Q4 (we’ve already installed Q5). Align the parts to match the outline printed on the board.

6. Install tacAle switches SW1 (UP), SW2 (OK), and SW3 (DOWN). These switches snap into the board and will hold themselves in while you solder them.

7. Solder everything down and trim the excess leads. This concludes today’s hardware assembly.

Procedure: ini/al display coding

8. Create a new MPlab project and connect your board to the programmer as in your previous lab. Create a new avr-main.c source ﬁle and type the following into it:

9. Create a new xc8_header.h ﬁle named funcAons.h and open it for ediAng. Delete whatever is there and paste in the source code from the funcAons.h ﬁle provided with the lab.

10.Build the source code and install in on your project. You should see it display 6837.

Procedure: coding a counter

Displaying 6837 is a bit of a feat, but were not done yet. Let’s make a counter out of it.

11.Modify your source code to iniAalize number to 0 instead of 6837;

12.Add a line of code aTer the last (ones) digit is displayed. This code will increment number by one. The code will look like this:

number++;

13.Build and install your code. It should count up rapidly. ATer it reaches 9999 strange stuﬀ will happen. We’ll ﬁx that later.

Procedure: coding a stopwatch

This counter increments about 125 Ames a second. We can slow it down to about 100 Ames per second by adding a decimal point aTer the second digit. The addiAonal Ame required to display the decimal point will slow the code down. With the decimal point it will be slowed to counAng around 100 Ames per second and we can consider it to be a (very approximate) stopwatch. We’ll deal with the accuracy next week.

14.Add a line of code in the while loop to display a decimal point in the second digit. The code will look like this:

display_digit(‘ . ’,2);

15.Build and install your code. You should see your project counAng more-or-less in seconds.

Procedure: adding some bu<ons

A stopwatch that isn’t accurate and can’t be stopped and started is not too useful. We’ll deal with the accuracy next week, but let’s address the start and stop funcAons now. We can check the buMons every Ame around the loop to control our stopwatch.

16.Add a new char type variable called run iniAalized to zero. This will be a mode for our stopwatch if it is zero the watch will be stopped, if it is 1 the watch will run. Put it in the code near where the other variables are declared:

char run = 0;

17.Change your code so that number is only incremented if the run variable is 1.

if (run == 1)

{

number++;

}

18.Add a test for the UP buMon (bit 0 of PORTE) to start the clock if it is pressed:

if ((PORTE_IN & 0b00000001) == 0)

{

run = 1; // enter run mode

}

19.Compile and load your code. Your project should display 00.00 unAl you press the top buMon. Then it should begin counAng.

20.The stopwatch sAll behaves badly when it reaches 99.99 seconds. Add an IF

statement to set run = 0 if number is equal to 9999. Where should this code go? 21.Add a test for the OK buMon to stop the watch if you press it.

22.Add a test for the DOWN buMon to reset number to zero if you press it. 23.number isn’t such a great name for a variable. Let’s change it.

23.1.Double click on any instance of the number variable.

23.2.Right click and select Refactor. Select Rename. A new dialog box will open. 23.3.Type in a beMer name, maybe ‘hundredths’ or something like that.

23.4.Click on the Refactor buMon. All instances will be changed.

24.Test your code. When you are happy with it, ask your TA to verify that it works. This will be part of your grade for this lab.

25.Check your stopwatch against another stopwatch (e.g. your phone). What is the real elapsed Ame when your stopwatch hits 99.99 seconds?

26.Take a screenshot of your code. It should be neatly formaMed and commented for clarity.

27.Save this code for next week.

Procedure: Countdown Timer

We now have a program that counts from 0 to 99.99 seconds and then stops. With some modiﬁcaAons, we can turn our stopwatch into a Amer. Let’s make a Amer that counts down from 10, 20, or 30 seconds using the stopwatch code. The UP buMon will start a 10-second Amer, the OK buMon will start a 20-second Amer, and the DOWN buMon will start a 30-second Amer.

28.Create a new MPLAB project. Create a new header and source ﬁle, and copy and paste the header ﬁle and the code for your stopwatch into these ﬁles.

29.We have seen how to increment a variable’s value by 1 using two plus signs. Similarly, we can decrement by one using two minus signs::

hundredths—-;

Modify your code to count down instead of up.

30.Modify the IF statements that check the buMons. The UP buMon should load the value for 10 seconds into the hundredths variable and start the Amer. The OK and DOWN buMons should also start the Amer, but load hundredths with values for 20 and 30 seconds, respecAvely. When you press the buMon, the display should update to the corresponding seconds. When you release the buMon, the Amer should immediately begin counAng down.

31.Similarly to the stopwatch, your Amer should stop counAng when it reaches 0. Modify your code so that it stops counAng when hundredths = 0.

32.We now have a Amer that can count down from 10, 20, or 30 seconds. Let’s add an auditory cue that the Amer has expired. We can employ the buzzer from lab 7 to accomplish this. Add a funcAon to create a sound from the buzzer for a few seconds. We can use a WHILE loop with a < operator to bend the buzzer a deﬁned number of Ames, as in this example:

Place this code in a new funcAon (not your main func;on) and give the funcAon a suitable name. When the buzzer sounds, the LED display will not be on. This is expected behavior.

33.Add a call to your buzzer funcAon. The buzzer should go oﬀ once when the Amer reaches 0, but it should not go oﬀ conAnuously. Try to ﬁgure out how to make the buzzer go oﬀ when the Amer reaches 0. The buzzer should sound for a few seconds and then stop buzzing. A nested IF statement might be useful here since two condiAons need to be true before the buzzer sounds.

34.You can modify the _delay_ms argument (change 1 to something else) to get diﬀerent “notes” from your buzzer. You can also change the WHILE condiAon (say, from 2000 to 3000) to adjust the buzzer duraAon. Make it around 3 seconds.

35.When you are happy with your code, please ask a TA to verify its operaAon. This will be part of your grade.

36.Screenshot your code. Your code should be neat and commented for clarity.

37.Answer the quiz quesAons. You will be asked to upload images of your stopwatch and Amer code.