Hi, we are making a arduino project consisting in show data that arduino has readed through a rfid reader shield in a LCD keypad shield, but we don't got to use the LCD while the rfid reader is connected. My doubt is if this two shields are compatible and, if they are, how we can make work both shields at the same time. Thanks for the attention.
Your problem is that these shields use the same pins.
You have to change pins used by the shields and alter your sketch accondingly.
The conflict is that the RFID uses pins D2 - D6 , and the LCD Keypad shield also uses D4, D5 and D6.
You can solve this by not stacking the shields, but wiring the LCD Keypad shield with jumper cables.
You can then select any pins you like, just not D2 - D6.
Don't forget to change the line containing: LiquidCrystal lcd(8, 9, 4, 5, 6, 7); accordingly.
Alternatively, you could use something like an i2c LCD that only uses 2 pins (pin A4/A5 on the Uno), and you can use other i2c devices on the same bus. Adafruit makes a version of the LCD shield that uses i2c: LCD Shield Kit w/ 16x2 Character Display - Only 2 pins used! [BLUE AND WHITE] : ID 772 : $19.95 : Adafruit Industries, Unique & fun DIY electronics and kits, but if you look around, there are various i2c displays that don't use a shield.