Capacitive Touch Sensor Breakout — MPR121

This is a break­out board for Freescale’s MPR121QR2. The MPR121 is a capac­i­tive touch sen­sor con­troller dri­ven by an I2C inter­face. The chip can con­trol up to twelve indi­vid­ual elec­trodes, as well as a sim­u­lat­ed thir­teenth elec­trode. The MPR121 also fea­tures eight LED dri­ving pins. When these pins are not con­fig­ured as elec­trodes, they may be used to dri­ve LEDs.There a four jumpers on the bot­tom of the board, all of which are set (closed) by default. An address jumper ties the ADD pin to ground, mean­ing the default I2C address of the chip will be 0x5A. If you need to change the address of the chip (by short­ing ADD to a dif­fer­ent pin), make sure you open the jumper first. Jumpers also con­nect SDA, SCL and the inter­rupt pin to 10k pull-up resis­tors. If you don’t require the pull-up resis­tors you can open the jumpers by cut­ting the trace con­nect­ing them.There is no reg­u­la­tion on the board, so the volt­age sup­plied should be between 2.5 and 3.6VDC. The VREG pin is con­nect­ed through a 0.1uF capac­i­tor to ground, which means, unless you mod­i­fy the board, you can’t oper­ate the MPR121 in low-sup­ply volt­age mode (1.71–2.75VDC).DOCUMENTSSchemat­icEagle FilesDatasheet (MPR121QR)Exam­ple Code (ATmega328)Hookup GuideBil­dr Tuto­r­i­alGitHub