Aperçu technique - protocole
Généralités
Le protocole de communication USB est très simple, avec seulement une communication du périphérique vers le PC hôte (aucune transmission de données du PC vers le périphérique). Tous les transferts ont la même longueur de 8 octets. Ainsi, aucune action n'est possible sur les leds à partir du PC.
Chaque touche appuyée / relâchée provoque le changement d'un bit (1 / 0) dans le message de 8 octets, ces changements sont cumulés (OU logique). L'état vert / rouge des leds est disponible sur le bit 3 de l'octet 8. Les appuis / relâche des boutons leds sont également enregistrés sur les bits 2 / 1 de l'octet 8.
Table de correspondance entre messages de huit octets et numéro de touche
Touche Séquence d'octets (hex) Touche Séquence d'octets (hex) 1 01 00 00 00 00 00 00 00 25 00 00 00 01 00 00 00 00 2 02 00 00 00 00 00 00 00 26 00 00 00 02 00 00 00 00 3 04 00 00 00 00 00 00 00 27 00 00 00 04 00 00 00 00 4 08 00 00 00 00 00 00 00 28 00 00 00 08 00 00 00 00 5 10 00 00 00 00 00 00 00 29 00 00 00 10 00 00 00 00 6 20 00 00 00 00 00 00 00 30 00 00 00 20 00 00 00 00 7 40 00 00 00 00 00 00 00 31 00 00 00 40 00 00 00 00 8 80 00 00 00 00 00 00 00 32 00 00 00 80 00 00 00 00 9 00 01 00 00 00 00 00 00 33 00 00 00 00 01 00 00 00 10 00 02 00 00 00 00 00 00 34 00 00 00 00 02 00 00 00 11 00 04 00 00 00 00 00 00 35 00 00 00 00 04 00 00 00 12 00 08 00 00 00 00 00 00 36 00 00 00 00 08 00 00 00 13 00 10 00 00 00 00 00 00 37 00 00 00 00 10 00 00 00 14 00 20 00 00 00 00 00 00 38 00 00 00 00 20 00 00 00 15 00 40 00 00 00 00 00 00 39 00 00 00 00 40 00 00 00 16 00 80 00 00 00 00 00 00 40 00 00 00 00 80 00 00 00 17 00 00 01 00 00 00 00 00 41 00 00 00 00 00 01 00 00 18 00 00 02 00 00 00 00 00 42 00 00 00 00 00 02 00 00 19 00 00 04 00 00 00 00 00 43 00 00 00 00 00 04 00 00 20 00 00 08 00 00 00 00 00 44 00 00 00 00 00 08 00 00 21 00 00 10 00 00 00 00 00 45 00 00 00 00 00 10 00 00 22 00 00 20 00 00 00 00 00 46 00 00 00 00 00 20 00 00 23 00 00 40 00 00 00 00 00 47 00 00 00 00 00 40 00 00 24 00 00 80 00 00 00 00 00 48 00 00 00 00 00 80 00 00 49 00 00 00 00 00 00 01 00 Vert 00 00 00 00 00 00 00 01 50 00 00 00 00 00 00 02 00 Rouge 00 00 00 00 00 00 00 02 Aucun bouton appuyé, état led verte 00 00 00 00 00 00 00 00 Aucun bouton appuyé, état led rouge 00 00 00 00 00 00 00 04