Here is the information that allowed me to make it work:
root @ # lsusb Raspi
Bus 001 Device 005: ID 148f: 7601 Ralink Technology, Corp.
Installation information found on the page [...]
wget ftp://ftp.meta5.com/MT7601Usta.tar.gz
tar xvzf MT7601Usta.tar.gz
cd MT7601Usta
./install.sh
modprobe MT7601Usta
Edit / etc / network / interfaces
auto lo
iface lo inet loopback
iface eth0 inet dhcp
self ra0
allow-hotplug ra0
inet dhcp iface ra0
wpa-scan-ssid 1
wpa-ap-scan 1
wpa-key-mgmt WPA-PSK
wpa-proto WPA RSN
wpa-pairwise CCMP TKIP
wpa-group CCMP TKIP
wpa-ssid "WIFI_SSID"
wpa-psk "XXXXXXXXXXXX"
Start-up
ifup ra0
And then it works properly!