From d9ca3885d654a5c9b5f0231c9bc2d60e3752496f Mon Sep 17 00:00:00 2001
From: "Mark A. Yoder" <Mark.A.Yoder@Rose-Hulman.edu>
Date: Tue, 10 Oct 2023 17:38:21 -0400
Subject: [PATCH] Added \Your turn" exercises.
---
intro/blinkLED.rst | 72 +++++++++++++++++++++++++++++++++++-----------
1 file changed, 55 insertions(+), 17 deletions(-)
diff --git a/intro/blinkLED.rst b/intro/blinkLED.rst
index ca5d7ce0..d504ff52 100644
--- a/intro/blinkLED.rst
+++ b/intro/blinkLED.rst
@@ -241,7 +241,7 @@ internal LEDs.
.. code-block:: shell-session
- bone:~$ cat blinkInternalLED.py
+ bone:~$ cat blinkInternalLED.sh
LED="3"
LEDPATH='/sys/class/leds/beaglebone:green:usr'
@@ -252,7 +252,7 @@ internal LEDs.
echo "0" > ${LEDPATH}${LED}/brightness
sleep 0.5
done
- bone:~$ ./blinkInternalLED.py
+ bone:~$ ./blinkInternalLED.sh
^c
Here you see a simple bash script that turns an LED
@@ -290,17 +290,31 @@ Here's a script that sequences the LEDs on and off.
while True:
for i in range(LEDs):
f[i].seek(0)
- f[i].write("1")
+ f[i].write("1") # 1 turns the LED on
time.sleep(0.25)
for i in range(LEDs):
f[i].seek(0)
- f[i].write("0")
+ f[i].write("0") # 0 turns the LED off
time.sleep(0.25)
bone:~$ ./seqLEDs.py
^c
Again, hit Ctrl+c to stop the script.
+This python script is a bit more complicated that the previous bash
+script. Note that *LEDPATH* is the same in both scripts. They use the
+same interface to control the built-in LEDs. The python script opens a
+file for each of the LEDs and then writes a **1** to the file to turn on
+the LED. A **0** is writen to turn it off. The *for* loop allows it to turn
+on (or off) all four LEDs in sequence.
+
+Your turn
+^^^^^^^^^
+
+Try speeding up, or slowing down the sequencing by changing the *sleep* times.
+If you have programming experience, make a single LED sequence back and forth.
+
+
Blinking from Command Line
--------------------------
@@ -325,8 +339,8 @@ You can blink any of them. Let's try ``usr1``.
bone:~$ echo 1 > brightness
bone:~$ echo 0 > brightness
-When you echo 1 into ``brightness`` the LED turns on.
-Echoing a 0 turns it off.
+When you echo **1** into ``brightness`` the LED turns on.
+Echoing a **0** turns it off.
Blinking other LEDs
-------------------
@@ -336,7 +350,7 @@ directories and doing the same. Let's blink the USR0 LED.
.. code-block:: shell-session
- bone:~$ cd ../beaglebone\:green\:usr0/
+ bone:~$ cd ./sys/class/leds/beaglebone\:green\:usr0/
bone:~$ echo 1 > brightness
bone:~$ echo 0 > brightness
@@ -362,8 +376,10 @@ what triggers you can set:
Notice ``[heartbeat]`` is in brackets. This shows it's the
current trigger. The echo changes the trigger to ``none``.
+Your turn
+^^^^^^^^^
Try experimenting with some of the other triggers and see if you
-can figure them out.
+can figure them out. Try changing the trigger on the other LEDs.
Another way to Blink an LED
---------------------------
@@ -401,21 +417,26 @@ the ``gpioset`` command.
The first command sets chip 1, line 22 (the usr1 LED) to 1 (on) for
2 seconds. The second command turns it off for 2 seconds.
-Try it for the other LEDs.
+Your turn
+^^^^^^^^^
+
+Try turning on and off the other LEDs. If you have programming experience,
+try modifying the earler *bash* script to use `gpiod` instead of `echo`.
.. note::
- This may not work on all Beagles since it depends on which
+ The following may not work on all Beagles since it depends on which
version of Debian you are running.
-Blinking in response to a button
+Blinking in response to a button
---------------------------------
-Some Beagles have a USR button that can be used to control the LEDs.
-You can test the USR button with ``evtest``
+Some Beagles have a **USR** button that can be used to control the LEDs.
+You can test the **USR** button with ``evtest``
.. code-block:: shell-session
+ bone:~$ sudo apt install evtest
bone:~$ evtest
No device specified, trying to scan all of /dev/input/event*
Not running as root, no devices may be available.
@@ -456,8 +477,11 @@ the USR button and you'll see:
Event: time 1692994988.641754, -------------- SYN_REPORT ------------
Ctrl+c
-The following script uses evtest to wait for the USR button to be pressed and
-then turns on the LED.
+The value **1** means the **USR** button was pressed, the **0** means it
+was released. The value **2** means the button is being held.
+
+The following script uses ``evtest`` to wait for the **USR** button to be
+pressed and then turns on the LED.
.. literalinclude:: buttonEvent.sh
:caption: buttonEvent.sh
@@ -465,9 +489,23 @@ then turns on the LED.
:download:`buttonEvent.sh<buttonEvent.sh>`
-Try running it and pressing the USR button.
+Try running it and pressing the **USR** button.
+
+.. code-block:: shell-session
+
+ bone:~$ ./buttonEvent.sh
+ ^c
+
+The **USR3** LED should turn on when the **USR** button is pressed.
+
+Your turn
+^^^^^^^^^
+Try modifying the code to turn on a different LED. Try blinking 2 or 3
+LEDs when the button is pressed. Can you toggle an LED each time the
+button is pressed?
-The next script polls the USR button and toggles the LED.
+The next script polls the USR button and toggles the LED rather that waiting
+for an event.
.. literalinclude:: buttonLED.sh
:caption: buttonLED.sh
--
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