Difference between revisions of "SPEd 2013 Workshop"

From eLinux.org
Jump to: navigation, search
m (BoneScript IO: Added section)
m
 
(7 intermediate revisions by the same user not shown)
Line 1: Line 1:
 
[[Category:ECE497 |Workshop]]
 
[[Category:ECE497 |Workshop]]
 
{{YoderHead}}
 
{{YoderHead}}
Here are the labs for the afternoon Linux part of the [http://dspe2013.engr.scu.edu/training.html#yoder SPEd2013 Workshop]
+
Here are the labs for the the [http://dspe2013.engr.scu.edu/training.html#yoder SPEd2013 Workshop]
  
 
== Wiring Up ==
 
== Wiring Up ==
Line 36: Line 36:
 
# Click '''run''' (you wired the pot to P9_36).  Change the pot and click '''run''' again.
 
# Click '''run''' (you wired the pot to P9_36).  Change the pot and click '''run''' again.
 
# Play around
 
# Play around
 +
 +
== Cloud 9 ==
 +
# Open Cloud 9 via '''http://192.168.7.2:3000'''
 +
# Open '''analog2.js'''
 +
# Change the IO pins to match what you've wired
 +
# Save the file (ctrl-s) and click '''run'''
 +
# Play around
 +
# Open '''blinkled.js''' and repeat the steps above.
  
 
== Linux Warm Up ==
 
== Linux Warm Up ==
Line 90: Line 98:
 
Try this:
 
Try this:
 
  bone$ '''cd /sys'''
 
  bone$ '''cd /sys'''
  bone$ '''ls -F'''
+
  bone$ '''ls'''
  block/ bus/ class/ dev/ devices/ firmware/ fs/ kernel/ module/ power/
+
  block  bus  class  dev  devices  firmware  fs  kernel  module  power
  
 
The "'''/'''" after the name means it's a directory. Here we see several directories that represent hardware we can control. Explore a bit and see what you find.
 
The "'''/'''" after the name means it's a directory. Here we see several directories that represent hardware we can control. Explore a bit and see what you find.
Line 98: Line 106:
  
 
  beagle$ '''cd /sys/class'''
 
  beagle$ '''cd /sys/class'''
  beagle$ '''ls -F'''
+
  beagle$ '''ls'''
  backlight/ firmware/     lcd/      mtd/          scsi_disk/   ubi/
+
  backlight  firmware    leds      power_supply  scsi_host   uio
  bdi/       gpio/         leds/     net/           scsi_host/  udc/
+
  bdi        gpio        mbox     pwm           sound      usbmon
  block/     graphics/     mbox/      power_supply/ sound/      uio/
+
  block      graphics    mdio_bus rc            spi_master  vc
  bluetooth/ hwmon/       mdio_bus/  regulator/     spi_master/  usbmon/
+
  bluetooth  hwmon        mem      regulator    spidev      video4linux
  bsg/       i2c-adapter/ mem/      rfkill/       spidev/      vc/
+
  bsg        i2c-adapter  misc      rfkill        thermal    vtconsole
  dma/       i2c-dev/      misc/     rtc/           thermal/    vtconsole/
+
  dma        i2c-dev      mmc_host  rtc          tty        watchdog
  drm/       input/       mmc_host/  scsi_device/   tty/        watchdog/
+
  drm        input        mtd      scsi_device  ubi
 +
dvb        lcd          net      scsi_disk    udc
  
Explore some.
+
Explore some.
  
 
=== Blinking a USR LED ===
 
=== Blinking a USR LED ===
Line 113: Line 122:
  
 
  bone$ '''cd /sys/class/leds'''
 
  bone$ '''cd /sys/class/leds'''
  bone$ '''ls -F'''
+
  bone$ '''ls'''
 
  beaglebone:green:usr0  beaglebone:green:usr2
 
  beaglebone:green:usr0  beaglebone:green:usr2
 
  beaglebone:green:usr1  beaglebone:green:usr3
 
  beaglebone:green:usr1  beaglebone:green:usr3
Line 120: Line 129:
  
 
  bone$ '''cd beagleboard\:\:usr0'''
 
  bone$ '''cd beagleboard\:\:usr0'''
  bone$ '''ls -F'''
+
  bone$ '''ls'''
  brightness  device@ max_brightness  power/ subsystem@ trigger  uevent
+
  brightness  device  max_brightness  power  subsystem  trigger  uevent
  
(The "'''@'''" after the name means it's a link.)  See what's in '''brightness''', '''max_brightness''' and '''trigger''' by using the <code>cat</code> command.  For example:
+
See what's in '''brightness''', '''max_brightness''' and '''trigger''' by using the <code>cat</code> command.  For example:
  
 
  bone$ '''cat trigger'''
 
  bone$ '''cat trigger'''
Line 146: Line 155:
 
  [none] mmc0 timer heartbeat backlight gpio default-on  
 
  [none] mmc0 timer heartbeat backlight gpio default-on  
 
  bone$ '''echo timer > trigger'''
 
  bone$ '''echo timer > trigger'''
  bone$ '''ls -F'''
+
  bone$ '''ls'''
  brightness  delay_on  max_brightness  subsystem@ uevent
+
  brightness  delay_on  max_brightness  subsystem  uevent
  delay_off  devicepower/          trigger
+
  delay_off  device   power           trigger
 
  bone$ '''echo 100 > delay_on'''
 
  bone$ '''echo 100 > delay_on'''
 
  bone$ '''echo 900 > delay_off'''
 
  bone$ '''echo 900 > delay_off'''
Line 156: Line 165:
 
=== Blinking an External LED via gpio ===
 
=== Blinking an External LED via gpio ===
  
Earlier we wired an LED to the P9_12 General Purpose IO (gpio) port and controlled it via BoneScript.  Here we'll control it via a shell command. First we need to figure out which gpio pin P9_12 is attached to.  The following figure shows it attached to gpio_60.
+
Earlier we wired an LED to the P9_11 General Purpose IO (gpio) port and controlled it via BoneScript.  Here we'll control it via a shell command. First we need to figure out which gpio pin P9_12 is attached to.  The following figure shows it attached to gpio_30.
  
 
[[File:P9PWMs.jpg | 600px]]
 
[[File:P9PWMs.jpg | 600px]]
  
 
Here's how you turn it on
 
Here's how you turn it on
 
 
  bone$ '''cd /sys/class/gpio'''
 
  bone$ '''cd /sys/class/gpio'''
  bone$ '''ls -F'''
+
  bone$ '''ls'''
  export  gpiochip0@ gpiochip32@  gpiochip64@ gpiochip96@ unexport
+
  export  gpio22 gpio31  gpio7      gpiochip32  gpiochip96
 +
gpio20  gpio23  gpio50  gpiochip0  gpiochip64 unexport
  
 +
(Yours may look different depending on what you have used with BoneScript.)
 
Presently no gpio pins are visible.  You need to tell it which pin to export
 
Presently no gpio pins are visible.  You need to tell it which pin to export
  
  bone$ '''echo 60 > export'''
+
  bone$ '''echo 30 > export'''
  bone$ '''ls -F'''
+
  bone$ '''ls'''
  export  gpio60@ gpiochip0@ gpiochip32@ gpiochip64@  gpiochip96@ unexport
+
  export  gpio22 '''gpio30''' gpio50 gpiochip0  gpiochip64  unexport
 +
gpio20  gpio23  gpio31  gpio7  gpiochip32  gpiochip96
  
Notice '''gpio60''' has appeared.  All we need to do is tell it which direction and then turn it on.
+
Notice '''gpio30''' has appeared.  All we need to do is tell it which direction and then turn it on.
  
  bone$ '''cd gpio60'''
+
  bone$ '''cd gpio30'''
 
  bone$ '''ls'''
 
  bone$ '''ls'''
 
  active_low  direction  edge  power  subsystem  uevent  value
 
  active_low  direction  edge  power  subsystem  uevent  value

Latest revision as of 15:29, 7 August 2013

thumb‎ Embedded Linux Class by Mark A. Yoder


Here are the labs for the the SPEd2013 Workshop

Wiring Up

First wire up an LED, switch and a potentiometer. The table below shows what pins are available. The LED and switch can go on any GPIO (general purpose IO) pin. The pot goes on one of the AIN (analog in) pins.

                 P9                                       P8

P9PWMs.jpg

Wiring an LED

Take an LED and attach the long lead (anode) into pin P9_11. That is, pin 11 on the P9 (left) header. Put the short lead on a column on the breadboard. Put one end of the 270Ω resistor in the same column as the LED and the other end in pin P9_1 (GND).

Wiring a switch

Attach one end of the switch on P9_2 (GND) and the other on P9_13. If you don't have a switch, put one end of a wire in P9_2 and touch the other end to P9_13 when you want to turn it on.

Wiring a potentiometer

Attach the middle pin of the pot to P9_36 (AIN5). Place one of the outer pins to P9_32 (Vdd_ADC) which is a 3.3V analog reference. Place the other on pin P9_34 (GNDA_ADC) the analog ground.

IO via BoneScript

Writing a pin

  1. Click on the digitalWrite() link on the left column under BoneScript Functions.
  2. Click run and verify that the USR0 LED is on.
  3. Edit the code and replace 'USR0' with 'P9_11' (the pin you wired the LED to).
  4. Click run
  5. Play around

Reading a pin

  1. Click on the digitalRead() link on the left column under BoneScript Functions.
  2. Edit the code and replace 'P8_19' with 'P9_13' (the pin you wired the switch to).
  3. Click run. Push the switch and click run
  4. Play around

Can you modify the code to read the switch and turn on the LED in response?

Reading analog

  1. Click on the analogRead() link on the left column under BoneScript Functions.
  2. Click run (you wired the pot to P9_36). Change the pot and click run again.
  3. Play around

Cloud 9

  1. Open Cloud 9 via http://192.168.7.2:3000
  2. Open analog2.js
  3. Change the IO pins to match what you've wired
  4. Save the file (ctrl-s) and click run
  5. Play around
  6. Open blinkled.js and repeat the steps above.

Linux Warm Up

PuTTYconfiguration.jpg

Before we can interact with LEDs and switches we need to learn some simple Linux commands.

  1. On your host computer, running Windows, start up puTTY.
  2. If you get a Security Warning, click Run.
  3. Enter 192.168.7.2 in the Host Name field and click Open
  4. Login as root with no password.
  5. Enter ls to list what files you have. You shouldn't see much.
PuTTYloging.jpg

At this point you need to learn a few simple Linux commands for creating and displaying files. Once you know these commands it's easy to turn an LED on and off.

First, let's edit a file using the nano editor. Nano is a simple editor that easy to learn. This will edit (and create) the file play.txt.

bone$ nano play.txt

Add a couple of lines of text to the file, it doesn't really matter what and then Exit. You can list the files in the current directory with ls and show the contents of a file with cat.

bone$ ls
Desktop  play.txt
bone$ cat play.txt
A couple of lines
of text.

Use echo to print a line of text.

bone$ echo This is a line of text
This is a line of text

Here's a powerful operator. You can take the output of any command and redirect it to a file with >.

bone$ echo This is a line of text > here.txt
bone$ cat here.txt
This is a line of text

We are almost there. Use cd to change directories. / is the top level directory.

bone$ cd /
bone$ ls
bin   dev  home  lost+found  mnt   run   sys  usr
boot  etc  lib   media       proc  sbin  tmp  var

If you ever get lost, cd alone takes you home.

bone$ cd
gone$ ls
Desktop  here.txt  play.txt

Now you are ready to flash an LED.

Blinking an LED

gpio via the Shell Command Line and sysfs

Another easy way to do general purpose I/O (gpio) on the Beagle is through a terminal window and a shell prompt. In Linux, almost everything is treated as a file, even things that aren't files. Here we'll use a virtual file system called sysfs. sysfs exposes the drivers for the hardware so you can easily use them.

Try this:

bone$ cd /sys
bone$ ls
block  bus  class  dev  devices  firmware  fs  kernel  module  power

The "/" after the name means it's a directory. Here we see several directories that represent hardware we can control. Explore a bit and see what you find.

Now try:

beagle$ cd /sys/class
beagle$ ls
backlight  firmware     leds      power_supply  scsi_host   uio
bdi        gpio         mbox      pwm           sound       usbmon
block      graphics     mdio_bus  rc            spi_master  vc
bluetooth  hwmon        mem       regulator     spidev      video4linux
bsg        i2c-adapter  misc      rfkill        thermal     vtconsole
dma        i2c-dev      mmc_host  rtc           tty         watchdog
drm        input        mtd       scsi_device   ubi
dvb        lcd          net       scsi_disk     udc

Explore some.

Blinking a USR LED

The Beagle Black has four user LEDS, user0 - user3, that you can control. Try this:

bone$ cd /sys/class/leds
bone$ ls
beaglebone:green:usr0  beaglebone:green:usr2
beaglebone:green:usr1  beaglebone:green:usr3

Here you see the directories for controlling each of the usr LEDs. By default, usr0 flashes a heartbeat pattern and usr1 flashes when the micro SD card is accessed. Let's control usr0.

bone$ cd beagleboard\:\:usr0
bone$ ls
brightness  device  max_brightness  power  subsystem  trigger  uevent

See what's in brightness, max_brightness and trigger by using the cat command. For example:

bone$ cat trigger
none nand-disk mmc0 timer oneshot [heartbeat] backlight gpio cpu0 default-on transient

This shows trigger can have many values. The present value is heartbeat. Check the LED, is it beating? You can stop the heartbeat via:

bone$ echo none > trigger
bone$ cat trigger
[none] nand-disk mmc0 timer oneshot heartbeat backlight gpio cpu0 default-on transient 

Did it stop beating? You can now turn it on and off with:

bone$ echo 1 > brightness
bone$ echo 0 > brightness

Is it responding correctly?

The Bone has more trigger options. Try:

bone$ cat trigger
[none] mmc0 timer heartbeat backlight gpio default-on 
bone$ echo timer > trigger
bone$ ls
brightness  delay_on  max_brightness  subsystem  uevent
delay_off   device    power           trigger
bone$ echo 100 > delay_on
bone$ echo 900 > delay_off

What does this do?

Blinking an External LED via gpio

Earlier we wired an LED to the P9_11 General Purpose IO (gpio) port and controlled it via BoneScript. Here we'll control it via a shell command. First we need to figure out which gpio pin P9_12 is attached to. The following figure shows it attached to gpio_30.

P9PWMs.jpg

Here's how you turn it on

bone$ cd /sys/class/gpio
bone$ ls
export  gpio22  gpio31  gpio7      gpiochip32  gpiochip96
gpio20  gpio23  gpio50  gpiochip0  gpiochip64  unexport

(Yours may look different depending on what you have used with BoneScript.) Presently no gpio pins are visible. You need to tell it which pin to export

bone$ echo 30 > export
bone$ ls
export  gpio22  gpio30  gpio50  gpiochip0   gpiochip64  unexport
gpio20  gpio23  gpio31  gpio7   gpiochip32  gpiochip96

Notice gpio30 has appeared. All we need to do is tell it which direction and then turn it on.

bone$ cd gpio30
bone$ ls
active_low  direction  edge  power  subsystem  uevent  value
bone$ echo out > direction
bone$ echo 1 > value

Your LED should be on!

bone$ echo 0 > value

Now it's off.

Reading a switch

Now that you have an LED working, wiring in a switch is easy. Earlier you wired a switch to P9_42, which from the table above is gpio_7.

Based on what you saw above.

bone$ cd /sys/class/gpio
bone$ echo 7 > export
bone$ cd gpio7
bone$ ls
bone$ echo in > direction
bone$ cat value
0

Now hold the button down and try again.

bone$ cat value
1

Once you have the switch and LED working use nano and put the following in a file.

bone$ cd  (Go back home)
bone$ nano button.sh
#!/bin/bash
cd /sys/class/gpio
while [ 1 ]
do
   cat gpio7/value
   sleep 0.25
done

Quit nano and run

bone$ chmod +x button.sh  (This makes button.sh executable)
bone$ ./button.sh

What happens when you push the button? Hit Ctrl-C to quit button.sh.

Now experiment around. Can you flash the LED? How fast? Make the LED read the switch.

Other Languages

Out-of-the-box the bone can run

  • C
  • C++
  • bash
  • perl
  • python
  • Javascript

Here's a simple C example

bone$ cd
bone$ nano hello.c
#include <stdio.h>
main ()
{
        printf("hello, world\n");
}
bone$ cc hello.c
bone$ ./a.out
hello, world

Try your favorite language.




thumb‎ Embedded Linux Class by Mark A. Yoder