A fairly feature complete library for the Resurgent Semiconductor MPR121QR2. This is a popular capacitive touch sense IC featuring:
- 12 electrodes/capacitance sensing inputs in which 8 are multifunctional for LED driving and GPIO
- Integrated independent autocalibration for each electrode input
- Autoconfiguration of charge current and charge time for each electrode input
- Separate touch and release trip thresholds for each electrode, providing hysteresis and electrode independence
- I2C interface, with IRQ Interrupt output to advise electrode status changes
This library was originally developed to support the Bare Conductive Pi Cap. However, it should work fine (with adaptations) for any Raspberry Pi connected to an MPR121.
Library includes support for:
- capacitive touch sensing
- proximity mode for virtual 13th electrode
- readback of filtered capacitance measurements
- full GPIO including PWM write
Still to be implemented:
- full support for autocalibration / autoconfig
- callback attachment for interrupt pin
- Requires WiringPi (
apt-get install wiringpi) - before you use any of the MPR121 methods, you need to call its MPR121.begin() method, normally in setup()
- the default MPR121 I2C address for this library is 0x5C, which is used if you call MPR121.begin()
- if you want to specify a different address you can, with MPR121.begin(yourAddress)
- You should install this code as part of the Pi Cap Raspbian package:
sudo apt-get install picap - However, if you are doing this yourself, clone the repository, enter it and run
make clean && make && make install - Note that you must run
make installas root, so you might need to prepend the command with sudo
// 0x5A for a lot of boards out there
// 0x5C for the Pi Cap
#define MPR121addr 0x5A
#include <MPR121.h>
void setup(){
MPR121.begin(MPR121addr);
}
void loop(){
// your code goes here
}
int main(void) {
setup();
while(1){
loop;
}
return(0);
}