View source for MPR121 touch sensor module

==Introduction== 

[[File:Mpr121-1.jpg|400px|]]

MPR121 touch sensor module is a kind of capacitive touch keyboard plate controlled by MPR121. It outputs the signal that the keys received form of IIC. The control principle and control mode are widely used in function modules of the key control in devices of household appliances (like washing machine, induction cooker etc.), MP3 player, remote control and mobile phones.
MPR121 touch sensor module collects, saves and transmits data through the MPR121 IC, which increases the induction sensitivity. As the operating voltage of MPR121 is 3.3V, it can carry out IIC communication with a control board whose operating voltage is also 3.3V. In addition, a SI5902DC chip and its pilot circuit is added to the MPR121 module to make sure the MPR121 module can work under 5V, and communicate with a control IC that support 5V, thus expanding the range of application of MPR121 module.

Note: the connection method varies when it is connected to different control board that works under different voltage. You are advised to connect carefully in light of the silk-screen instruction on the PCB. The 3.3v power supply should be connected to MPR121 module when it communicates with a 5v control board. (for more detailed information, please refer to chapter Ⅳ)

===Overview and Hardware Resources===

[[File:Mpr121 overview.jpg|600px|]]

Control IC: MPR121
Interface resources: 2 IIC connectors
Two power input ports: 3.3v and 5v
Weight: 13g
Size:  80mm*48mm*10mm

===Software=== 
[[Media:Arduino-1.0.1.zip]]

Test code program:
[[Media:MPR121 Touchpad.rar]]

=== data Source===

[[Media:MPR121.pdf]]

[[Media:SI5902DC.pdf]]

==Interface== 
===Interface Layout===

[[File:MPR121 layout.jpg|600px|]]

===Interface specifications===

The interface layout of MPR121 touch sensor module is displayed above. 
3.3v and 5v: for power supply

Common IRQ: when MPR121 communicates with a 3.3v or 5v CPU, it will send signals to the master control. The IRQ provides input when connected with a periphery controller.
3.3v CLK/ DATA pins: for IIC communication when connected to a 5v CPU.

CND: for ground

==Development Environment setting==
===Interface Connecting and Setting===
MPR121 touch sensor module can be connected and communicate with PCB whose operating voltage can be both 3.3v and 5v. As mentioned above, the connection method varies when connecting to different PCBs with different operating voltage. Here we set it as an example to connect it with Mega 2560.

[[File:Mega 2560 and mpr.jpg]]