{"id":5144,"date":"2018-10-15T06:00:40","date_gmt":"2018-10-15T05:00:40","guid":{"rendered":"https:\/\/www.blaess.fr\/christophe\/?p=5144"},"modified":"2019-01-27T09:06:32","modified_gmt":"2019-01-27T08:06:32","slug":"pilotage-de-gpio-avec-lapi-libgpiod-partie-1","status":"publish","type":"post","link":"https:\/\/www.blaess.fr\/christophe\/2018\/10\/15\/pilotage-de-gpio-avec-lapi-libgpiod-partie-1\/","title":{"rendered":"Pilotage de GPIO avec l’API Libgpiod (partie 1)"},"content":{"rendered":"\n

J’ai assist\u00e9 il y a quelques jours, lors de l’\u00e9dition 2018 des Kernel Recipes<\/a><\/em> \u00e0 une pr\u00e9sentation par Bartosz Golaszewski  de la nouvelle interface des GPIO pour l’espace utilisateur de Linux. J’en avais eu un bref aper\u00e7u il y a quelques mois mais je n’avais pas encore pris le temps d’essayer cette API. Cet article est donc une br\u00e8ve pr\u00e9sentation et mise en \u0153uvre de ces outils.<\/p>\n\n\n\n\n\n\n\n

Disponible depuis le noyau 4.8, cette API est amen\u00e9e \u00e0 remplacer l’acc\u00e8s via \/sys\/class\/gpio<\/code> qui est dor\u00e9navant consid\u00e9r\u00e9 comme deprecated<\/em>.<\/p>\n\n\n\n

L’acc\u00e8s se fait via le syst\u00e8me de fichiers devtmpfs<\/code> mont\u00e9 sur le r\u00e9pertoire \/dev<\/code>. On y trouve une entr\u00e9e par contr\u00f4leur de GPIO.<\/p>\n\n\n\n

<\/p>\n\n\n\n

Voici un exemple sur une carte Raspberry Pi 3, sur laquelle est install\u00e9e la distribution Raspbian 2018-06-27<\/code>.<\/p>\n\n\n\n

$ uname -a<\/strong>\nLinux raspberrypi 4.14.34-v7+ #1110 SMP Mon Apr 16 15:18:51 BST 2018 armv7l GNU\/Linux\n$ ls -l \/dev\/gpiochip*<\/strong>\ncrw-rw---- 1 root gpio 254, 0 Sep 16 08:34 \/dev\/gpiochip0\ncrw-rw---- 1 root gpio 254, 1 Sep 16 08:34 \/dev\/gpiochip1\ncrw-rw---- 1 root gpio 254, 2 Sep 16 08:34 \/dev\/gpiochip2
$
<\/pre>\n\n\n\n
Trois contr\u00f4leurs sont donc pr\u00e9sents sur cette carte.<\/p>\n\n\n\n
Acc\u00e8s depuis la ligne de commandes<\/h2>\n\n\n\n
[EDIT 2019] Dans les distributions Raspbian r\u00e9centes, il suffit d’installer les packages n\u00e9cessaires ainsi :<\/p>\n\n\n\n
$ sudo  apt  install  -y  gpiod  libgpiod-dev<\/strong><\/pre>\n\n\n\n
Dans les versions pr\u00e9c\u00e9dentes, la biblioth\u00e8que Libgpiod et ses utilitaires n’\u00e9taient pas encore packag\u00e9s<\/em> par Raspbian, il \u00e9tait alors n\u00e9cessaire de faire les op\u00e9rations suivantes. Je les laisse ici pour m\u00e9moire, d’autant que la version fournie par Raspbian 2018.11.13 est Libgpiod 1.0.1, et que la version actuelle est Libgpiod 1.2. Il y a des incompatibilit\u00e9s entre ces deux versions conduisant \u00e0 des erreurs de compilation lorsqu’on emploie les fonctionnalit\u00e9s trait\u00e9es dans le second article de cette s\u00e9rie. En attendant l’actualisation de Raspbian, je vous conseille de compiler la derni\u00e8re version stable comme suit.<\/p>\n\n\n\n
$ git clone https:\/\/git.kernel.org\/pub\/scm\/libs\/libgpiod\/libgpiod<\/strong>
Cloning into 'libgpiod'\u2026
remote: Counting objects: 3909, done.
remote: Total 3909 (delta 0), reused 0 (delta 0)
Receiving objects: 100% (3909\/3909), 569.10 KiB | 0 bytes\/s, done.
Resolving deltas: 100% (2691\/2691), done.
$ cd libgpiod\/<\/strong>
$ ls<\/strong>
autogen.sh  bindings  configure.ac  COPYING  Doxyfile  include  libgpiod.pc.in  Makefile.am  NEWS  README  src  tests
<\/pre>\n\n\n\n
$ sudo apt install autoconf autoconf-archive libtool<\/strong>
[...]
 $ .\/autogen.sh --enable-tools=yes --prefix=\/usr<\/strong>
autoreconf: Entering directory `.'
autoreconf: configure.ac: not using Gettext
autoreconf: running: aclocal --force -I m4
[...]
config.status: creating config.h
config.status: executing depfiles commands
config.status: executing libtool commands

$ make<\/strong>
make  all-recursive
make[1]: Entering directory '\/home\/pi\/libgpiod'
Making all in include
[...]
make[2]: Entering directory '\/home\/pi\/libgpiod'
make[2]: Leaving directory '\/home\/pi\/libgpiod'
make[1]: Leaving directory '\/home\/pi\/libgpiod'
 $ sudo make install<\/strong>
Making install in include
make[1]: Entering directory '\/home\/pi\/libgpiod\/include'
make[2]: Entering directory '\/home\/pi\/libgpiod\/include'
make[2]: Nothing to be done for 'install-exec-am'.
[...]
 \/usr\/bin\/install -c -m 644 libgpiod.pc '\/usr\/lib\/pkgconfig'
make[2]: Leaving directory '\/home\/pi\/libgpiod'
make[1]: Leaving directory '\/home\/pi\/libgpiod'
$
<\/pre>\n\n\n\n
Nous pouvons v\u00e9rifier tout de suite la liste des nouveaux outils install\u00e9s en tapant gpio<\/code> suivi de deux tabulations pour que le shell propose les compl\u00e9tions disponibles.<\/p>\n\n\n\n
$ gpio [TAB]<\/em> [TAB]<\/em><\/strong>\ngpio  gpiodetect  gpiofind  gpioget  gpioinfo  gpiomon  gpioset     
\n$<\/pre>\n\n\n\n
Hormis la commande gpio<\/code> elle-m\u00eame qui est associ\u00e9e \u00e0 la biblioth\u00e8que WiringPi<\/em> sp\u00e9cifique au Raspberry Pi, toutes les commande disponibles viennent d’\u00eatre ajout\u00e9es. Nous allons les examiner l’une apr\u00e8s l’autre.<\/p>\n\n\n\n
gpiodetect<\/h3>\n\n\n\n
La commande gpiodetect<\/code><\/strong> affiche la liste des contr\u00f4leurs GPIO d\u00e9tect\u00e9s, et pour chacun d’entre-eux le nom du driver associ\u00e9 et le nombre de lignes GPIO g\u00e9r\u00e9es.<\/p>\n\n\n\n
$ gpiodetect<\/strong>
gpiochip0 [pinctrl-bcm2835] (54 lines)
gpiochip1 [brcmexp-gpio] (8 lines)
gpiochip2 [brcmvirt-gpio] (2 lines)
\n$ <\/pre>\n\n\n\n
Il s’agit bien s\u00fbr de la m\u00eame liste que celle de \/dev\/gpio*<\/code>. Ces informations \u00e9taient d\u00e9j\u00e0 accessibles dans l’arborescence \/sys\/<\/code> ainsi :<\/p>\n\n\n\n
$ cd \/sys\/class\/gpio\/<\/strong>
\n$ for chip in gpiochip*; do echo $chip $(cat $chip\/label) $(cat $chip\/ngpio); done<\/strong>
gpiochip0 pinctrl-bcm2835 54
gpiochip100 brcmvirt-gpio 2
gpiochip128 brcmexp-gpio 8

$ <\/pre>\n\n\n\n
gpioinfo<\/h3>\n\n\n\n
La commande gpioinfo<\/code><\/strong> pr\u00e9sente l’\u00e9tat des lignes GPIO du contr\u00f4leur demand\u00e9.<\/p>\n\n\n\n
$ gpioinfo gpiochip2<\/strong>
gpiochip2 - 2 lines:
  line 0:  unnamed   \"led0\"  output  active-high [used]
  line 1:  unnamed   unused   input  active-high 
\n$<\/pre>\n\n\n\n
Si on ne pr\u00e9cise aucun contr\u00f4leur sur sa ligne de commande, gpioinfo<\/code> affiche les informations pour tous les contr\u00f4leurs.<\/p>\n\n\n\n
$ gpioinfo<\/strong>
gpiochip0 - 54 lines:
line 0: unnamed unused input active-high 
line 1: unnamed unused input active-high 
line 2: unnamed unused input active-high 
line 3: unnamed unused input active-high 
line 4: unnamed unused input active-high 
line 5: unnamed unused input active-high 
line 6: unnamed unused input active-high 
line 7: unnamed unused input active-high 
line 8: unnamed unused input active-high 
line 9: unnamed unused input active-high 
line 10: unnamed unused input active-high 
line 11: unnamed unused input active-high 
line 12: unnamed unused input active-high 
line 13: unnamed unused input active-high 
line 14: unnamed unused input active-high 
line 15: unnamed unused input active-high 
line 16: unnamed unused input active-high 
line 17: unnamed unused input active-high 
line 18: unnamed unused input active-high 
line 19: unnamed unused input active-high 
line 20: unnamed unused input active-high 
line 21: unnamed unused input active-high 
line 22: unnamed unused input active-high 
line 23: unnamed unused input active-high 
line 24: unnamed unused input active-high 
line 25: unnamed unused input active-high 
line 26: unnamed unused input active-high 
line 27: unnamed unused input active-high 
line 28: unnamed unused input active-high 
line 29: unnamed unused input active-high 
line 30: unnamed unused input active-high 
line 31: unnamed unused input active-high 
line 32: unnamed unused input active-high 
line 33: unnamed unused input active-high 
line 34: unnamed unused input active-high 
line 35: unnamed unused input active-high 
line 36: unnamed unused input active-high 
line 37: unnamed unused input active-high
line 38: unnamed unused input active-high
line 39: unnamed unused input active-high
line 40: unnamed unused input active-high
line 41: unnamed unused input active-high
line 42: unnamed unused input active-high
line 43: unnamed unused input active-high
line 44: unnamed unused input active-high
line 45: unnamed unused input active-high
line 46: unnamed unused input active-high
line 47: unnamed unused output active-high
line 48: unnamed unused input active-high
line 49: unnamed unused input active-high
line 50: unnamed unused input active-high
line 51: unnamed unused input active-high
line 52: unnamed unused input active-high
line 53: unnamed unused input active-high
gpiochip1 - 8 lines:
line 0: unnamed unused output active-high
line 1: unnamed unused output active-high
line 2: unnamed unused output active-high
line 3: unnamed unused output active-high
line 4: unnamed unused input active-high
line 5: unnamed unused output active-high
line 6: unnamed unused output active-high
line 7: unnamed \"led1\" input active-high [used]
gpiochip2 - 2 lines:
line 0: unnamed \"led0\" output active-high [used]
line 1: unnamed unused input active-high
$
<\/pre>\n\n\n\n

<\/p>\n\n\n\n
Les informations affich\u00e9es sont les suivantes.<\/p>\n\n\n\n