{"id":526,"date":"2014-08-14T15:13:47","date_gmt":"2014-08-14T14:13:47","guid":{"rendered":"http:\/\/ofalcao.pt\/blog\/?p=526"},"modified":"2014-08-14T15:13:47","modified_gmt":"2014-08-14T14:13:47","slug":"ev3dev-keypad-usb","status":"publish","type":"post","link":"https:\/\/ofalcao.pt\/blog\/2014\/ev3dev-keypad-usb","title":{"rendered":"ev3dev – keypad USB"},"content":{"rendered":"

Ter o LEGO Mindstorms EV3 a correr uma vers\u00e3o quase standard de Debian Linux come\u00e7a agora a revelar as suas vantagens: podemos atirar-lhe com quase tudo o que tivermos na nossa gaveta de sucata… como por exemplo um teclado num\u00e9rico USB:<\/p>\n

\"\"
USB Keypad (roline)<\/figcaption><\/figure>\n

O sistema operativo reconhece-o como um teclado convencional:<\/p>\n

root@ev3dev:~# dmesg\nusb 1-1.4.1: new low-speed USB device number 7 using ohci\ninput: USB-compliant keyboard as \/devices\/platform\/ohci.0\/usb1\/1-1\/1-1.4\/1-1.4.1\/1-1.4.1:1.0\/0003:0B38:0003.0001\/input\/input2\nhid-generic 0003:0B38:0003.0001: input: USB HID v1.10 Keyboard [USB-compliant keyboard] on usb-ohci.0-1.4.1\/input0\ninput: USB-compliant keyboard as \/devices\/platform\/ohci.0\/usb1\/1-1\/1-1.4\/1-1.4.1\/1-1.4.1:1.1\/0003:0B38:0003.0002\/input\/input3\nhid-generic 0003:0B38:0003.0002: input: USB HID v1.10 Mouse [USB-compliant keyboard] on usb-ohci.0-1.4.1\/input1<\/pre>\n
root@ev3dev:~# lsusb\nBus 001 Device 007: ID 0b38:0003 Gear Head Keyboard\nBus 001 Device 006: ID 058f:9254 Alcor Micro Corp. Hub<\/pre>\n
(o teclado tem embutido um hub USB de 2 portas da\u00ed o segundo device USB reportado)<\/p>\n
O sistema operativo cria entradas do tipo ‘event#’ em ‘\/dev\/input’ assim como apontadores com descritivos mais leg\u00edveis:<\/p>\n
ls \/dev\/input\/by-id\/ -la\nlrwxrwxrwx 1 root root\u00a0 10 Aug 13 23:38 usb-0b38_USB-compliant_keyboard-event-if01 -> ..\/event2\nlrwxrwxrwx 1 root root\u00a0 10 Aug 13 23:38 usb-0b38_USB-compliant_keyboard-event-kbd -> ..\/event1\n<\/pre>\n
De modo que o teclado pode ser referido por um destes dois ficheiros:<\/p>\n
    \n
  • \/dev\/input\/event1<\/li>\n
  • \/dev\/input\/usb-0b38_USB-compliant_keyboard-event-kbd<\/li>\n<\/ul>\n
    Enquanto que o sufixo “event1” \u00e9 vari\u00e1vel, o descritivo “by-id” n\u00e3o \u00e9 – no meu laptop Ubuntu o mesmo comando retorna:<\/p>\n
    ~$ ls \/dev\/input\/by-id\/ -la\nlrwxrwxrwx 1 root root\u00a0 10 Aug 13 23:38 usb-0b38_USB-compliant_keyboard-event-if01 -> ..\/event19\nlrwxrwxrwx 1 root root\u00a0 10 Aug 13 23:38 usb-0b38_USB-compliant_keyboard-event-kbd -> ..\/event18<\/pre>\n
    por isso \u00e9 prefer\u00edvel utilizar o descritivo “by-id”.<\/p>\n
    N\u00e3o \u00e9 suficiente ler os valores deste ficheiro – o primir de uma tecla gera gera um c\u00f3digo de v\u00e1rios caracteres aparentemente ininteligiveis:<\/p>\n
    ~$ cat \/dev\/input\/event1\nw\ufffd\ufffdS\ufffdV\u0001\u0004\u0004Sw\ufffd\ufffdS\ufffdV\u0001\u0001E\u0001w\ufffd\ufffdS\ufffdV\u0001w\ufffd\ufffdS\ufffdW\u0001\u0011w\ufffd\ufffdS\ufffdW\u0001w\ufffd\ufffdS\ufffd\ufffd\u0001\u0004\u0004Sw\ufffd\ufffdS\ufffd\ufffd\u0001\u0001Ew\ufffd\ufffdS\ufffd\ufffd\u0001^C<\/pre>\n
    A solu\u00e7\u00e3o \u00e9 usar o comando ‘showkey -s’ para descodificar. Por exemplo premindo a tecla ‘4’ com e sem ‘NumLock’ activo resulta:<\/p>\n
    cat \/dev\/input\/by-id\/usb-0b38_USB-compliant_keyboard-event-kbd > showkey -s<\/pre>\n
      \n
    • Sem Numlock: “^[[D”<\/li>\n
    • Com NumLock: “4”<\/li>\n<\/ul>\n
      Felizmente isto s\u00f3 \u00e9 necess\u00e1rio se quisermos ler directamente o teclado. Em situa\u00e7\u00f5es normais, quando os nossos programas est\u00e3o a correr, o pr\u00f3prio sistema operativo pode fazer esse trabalho por n\u00f3s. No caso do ev3dev podemos ler uma \u00fanica tecla a partir da consola com o seguinte comando bash:<\/p>\n
      read -s -n 1 Tecla < \/dev\/tty1<\/pre>\n
      O par\u00e2metro ‘-s’ serve para correr em modo silencioso (i.e. a tecla n\u00e3o \u00e9 simult\u00e2neamente escrita na consola) e o par\u00e2metro ‘-n 1’ for\u00e7a a leitura de um \u00fanico caracter (quanto ao pipe ‘< \/dev\/tty1’ descobri entretanto que tanto faz referir \/dev\/tty0 como \/dev\/tty1 portanto a partir daqui refiro a consola do ev3dev como \/dev\/tty1… porque sim)<\/p>\n
      O script abaixo junta esta informa\u00e7\u00e3o com a obtida anterior a respeito dos motores e permite controlar a rota\u00e7\u00e3o do motor com as teclas ‘4’ (LEFT) e ‘6’ (RIGHT), terminado com a tecla ‘ENTER’.<\/p>\n
      #!\/bin\/bash\n\n#chmod +x controlkey.sh\n\ntput clear > \/dev\/tty1\nsetfont \/usr\/share\/consolefonts\/Lat15-TerminusBold32x16.psf.gz\necho -n \"Prima tecla\" > \/dev\/tty1\n\nwhile true; do\n\n\u00a0 read -s -n 1 char < \/dev\/tty1\n\u00a0 if [[ \"$char\" = \"\" ]]; then\n\u00a0\u00a0\u00a0 break\n\u00a0 fi\n\n\u00a0 case \"$char\" in\n\n\u00a0 4) echo \"LEFT\" > \/dev\/tty1\n\n\u00a0\u00a0\u00a0\u00a0 echo\u00a0\u00a0 0 > \/sys\/class\/tacho-motor\/tacho-motor0\/duty_cycle_sp\n\u00a0\u00a0\u00a0\u00a0 echo\u00a0\u00a0 1 > \/sys\/class\/tacho-motor\/tacho-motor0\/run\n\u00a0\u00a0\u00a0\u00a0 echo\u00a0\u00a0 50 > \/sys\/class\/tacho-motor\/tacho-motor0\/duty_cycle_sp\n\u00a0\u00a0\u00a0\u00a0 sleep 1s\n\u00a0\u00a0\u00a0\u00a0 echo\u00a0\u00a0 0 > \/sys\/class\/tacho-motor\/tacho-motor0\/run\n\u00a0\u00a0\u00a0\u00a0 echo\u00a0\u00a0 0 > \/sys\/class\/tacho-motor\/tacho-motor0\/duty_cycle_sp\n\n\u00a0\u00a0\u00a0 ;;\n\n\u00a0 6) echo \"RIGHT\" > \/dev\/tty1\n\n\u00a0\u00a0\u00a0\u00a0 echo\u00a0\u00a0 0 > \/sys\/class\/tacho-motor\/tacho-motor0\/duty_cycle_sp\n\u00a0\u00a0\u00a0\u00a0 echo\u00a0\u00a0 1 > \/sys\/class\/tacho-motor\/tacho-motor0\/run\n\u00a0\u00a0\u00a0\u00a0 echo\u00a0\u00a0 -50 > \/sys\/class\/tacho-motor\/tacho-motor0\/duty_cycle_sp\n\u00a0\u00a0\u00a0\u00a0 sleep 1s\n\u00a0\u00a0\u00a0\u00a0 echo\u00a0\u00a0 0 > \/sys\/class\/tacho-motor\/tacho-motor0\/run\n\u00a0\u00a0\u00a0\u00a0 echo\u00a0\u00a0 0 > \/sys\/class\/tacho-motor\/tacho-motor0\/duty_cycle_sp\n\n\u00a0\u00a0\u00a0 ;;\n\u00a0\u00a0 esac\n\ndone\n\necho \"Bye!\" > \/dev\/tty1\n\n<\/pre>\n