Grove - 12 Key Capacitive I2C Touch Sensor V2 (MPR121)
The Grove - 12 Key Capacitive I2C Touch Sensor V2 (MPR121) is a multichannel proximity capacitive touch sensor. It's a 3-in-1 module with the following features: Capacitance Sensing, Touch Sensing, and Proximity Sensing.
Capacitance Sensing: This module uses a constant DC current capacitance sensing scheme. It can measure capacitances ranging from 10 pF to over 2000 pF with a resolution up to 0.01 pF.
Touch Sensing: Once the electrode capacitance data is acquired, the electrode touch/release status is determined comparing it to the capacitance baseline value.
Proximity Sensing: One new feature of the MPR121 is the near proximity sensing system. This means that all of the system’s electrodes can be summed together to create a single large electrode.
Based on Freescale MPR121, this sensor have 12 completely independent electrodes with build-in autoconfiguration. Thanks to I2C interface, you can detect all the 12 electrodes signals with only one Grove port, and the I2C address is hardware configurable, from 0X5B to 0X5D. This also makes it possible for multiple Grove - 12 Key Capacitive I2C Touch Sensor V2 (MPR121) to be used together for channel expansions in a single system, you can build a touch system which contains max. 36 electrodes.
This sensor is an upgrade version of Grove - I2C Touch Sensor, to meet Matsuzawa.Takashi's(one of our customer) needs, we make the I2C address changeable, and even cheaper than the old version. So if you have any suggestions about all the Groves, please just shoot to us. We will always listen to your voice, it may make another upgrade, even a new grove. Please kindly write your suggestions in the Grove 100+ page.
|Item||Grove - 12 Key Capacitive I2C Touch Sensor V2||Grove - I2C Touch Sensor|
|I2C Address||changeable(0X5B ~ 0X5D)||unmodifiable(0X5A)|
|Touch Sensor Feeler||x||√|
|Input Interface||alligator interface||DIP 2Pin Female Header|
|Release Time||September 11-2018||October 31-2015|
- Internal 10-bit ADC
- Integrated independent autocalibration for each electrode input
- Completely independent electrodes with built-in autoconfiguration
- I2C interface, with IRQ Interrupt output to advise electrode status changes
- Hardware configurable I2C address
- 12 electrodes/capacitance sensing inputs in which 8 are multifunctional for LED driving and GPIO
- 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
|Operating voltage||3.3V / 5V|
|Operating temperature||-40°C to +85°C|
|Storage Temperature Range||-40°C to +125°C|
|Capacitances ranging||10 pF to over 2000 pF|
|GPIO Source Current per Pin||12 mA|
|GPIO Sink Current per Pin||1.2 mA|
|I2C addrss range||0x5B,0x5C,0x5D|
|Default I2C address||0x5B|
- PC Peripherals
- MP3 Players
- Remote Controls
- Mobile Phones
- Lighting Controls
|Pin Number||Pin Name||Function||Pin multiplexing|
|8||CH0||Channel0, Electrode 0, input the capacitance valnue||-|
|9||CH1||Channel1, Electrode 1, input the capacitance valnue||-|
|10||CH2||Channel2, Electrode 2, input the capacitance valnue||-|
|11||CH3||Channel3, Electrode 3, input the capacitance valnue||-|
|12||CH4||Channel4, Electrode 4, input the capacitance valnue||GPIO or LED driver|
|13||CH5||Channel5, Electrode 5, input the capacitance valnue||GPIO or LED driver|
|14||CH6||Channel6, Electrode 6, input the capacitance valnue||GPIO or LED driver|
|15||CH7||Channel7, Electrode 7, input the capacitance valnue||GPIO or LED driver|
|16||CH8||Channel8, Electrode 8, input the capacitance valnue||GPIO or LED driver|
|17||CH9||Channel9, Electrode 9, input the capacitance valnue||GPIO or LED driver|
|18||CH10||Channel10, Electrode 10, input the capacitance valnue||GPIO or LED driver|
|19||CH11||Channel11, Electrode 11, input the capacitance valnue||GPIO or LED driver|
For the CH0 ~ CH11, once the electrode capacitance data is acquired, the electrode touch/release status is determined comparing it to the capacitance baseline value. And you can set the baseline value for each channel separately. The Pin12 ~ Pin19 is multifunctional, which means you can configure them as GPIO or LED driver, for more detail, please refer to the freescale application note AN3894.
The central pad is connected to the address wire, you can change the I2C address by cutting the wire and re-welding it. For the safety of you and others, please be careful with knife or welding gun you may use.
The operation voltage of Freescale MPR121 is 1.71V to 3.6V, however, the voltage of Arduino is 3.3V or 5V. In order to make it compaticable with 5V system, we use a voltage conversion chip to provide 3.3V for the Freescale MPR121.
Bi-directional level shifter circuit
This is a typical Bi-directional level shifter circuit to connect two different voltage section of an I2C bus. The I2C bus of this sensor use 3.3V, if the I2C bus of the Arduino use 5V, this circuit will be needed. In the schematic above, Q1 and Q2 are N-Channel MOSFET 2N7002A, which act as a bidirectional switch. In order to better understand this part, you can refer to the AN10441
The platforms mentioned above as supported is/are an indication of the module's software or theoritical compatibility. We only provide software library or code examples for Arduino platform in most cases. It is not possible to provide software library / demo code for all possible MCU platforms. Hence, users have to write their own software library.
Play With Arduino
In this part, we will show you how to use the Grove - 12 Key Capacitive I2C Touch Sensor V2 (MPR121) as a touch sensor, as for how to configure it as a Capacitance Sensor or Proximity Sensor, please check the Datasheet.
|Seeeduino V4.2||Base Shield||I2C Touch Sensor V2|
|Get One Now||Get One Now||Get One Now|
1 Please plug the USB cable gently, otherwise you may damage the port. Please use the USB cable with 4 wires inside, the 2 wires cable can't transfer data. If you are not sure about the wire you have, you can click here to buy
2 Each Grove module comes with a Grove cable when you buy. In case you lose the Grove cable, you can click here to buy.
Step 1. Connect the Grove - 12 Key Capacitive I2C Touch Sensor V2 (MPR121) to the I2C port of the Base Shield.
Step 2. Plug Grove - Base Shield into Seeeduino.
Step 3. Connect Seeeduino to PC via a USB cable.
If we don't have Grove Base Shield, We also can directly connect this module to Seeeduino as below.
If this is the first time you work with Arduino, we strongly recommend you to see Getting Started with Arduino before the start.
Step 1. Download the Grove touch sensor MPR121 Library from Github.
Step 2. Refer to How to install library to install library for Arduino.
Step 3. Restart the Arduino IDE. Open the example, you can open it in the following three ways：
Open it directly in the Arduino IDE via the path: File --> Examples --> Grove touch sensor MPR121 --> MPR121_demo.
Open it in your computer by click the MPR121_demo.ino which you can find in the xxxx\Arduino\libraries\Grove_touch_sensor_MPR121-master, XXXX is the location you installed the Arduino IDE.
Or, you can just click the icon in upper right corner of the code block to copy the following code into a new sketch in the Arduino IDE.
Serial.println("Can't detect device!!!!");
Serial.println("mpr121 init OK!");
if(result&(1<<i)) /*key i is pressed!!*/
Step 4. Upload the demo. If you do not know how to upload the code, please check How to upload code.
Step 5. Open the Serial Monitor of Arduino IDE by click Tool-> Serial Monitor. Or tap the
mkey at the same time. Set the baud rate to 115200.
If everything goes well, you will get the result. When you touch the CH0 ~ CH11 pads, it will trigger key ?pressed and key ?release
mpr121 inmpr121 init OK!
Play With Raspberry Pi
- Step 1. Things used in this project:
|Raspberry pi||Grove Base Hat for RasPi||I2C Touch Sensor V2|
|Get ONE Now||Get ONE Now||Get ONE Now|
- Step 2. Plug the Grove Base Hat into Raspberry.
- Step 3. Connect the Grove - 12 Key Capacitive I2C Touch Sensor V2 (MPR121) to the I2C port of the Base Hat.
- Step 4. Connect the Raspberry Pi to PC through USB cable.
If you are using Raspberry Pi with Raspberrypi OS >= Bullseye, you have to use this command line only with Python3.
- Step 1. Follow Setting Software to configure the development environment.
- Step 2. Download the source file by cloning the grove.py library.
git clone https://github.com/Seeed-Studio/grove.py
- Step 3. Excute below command to run the code.
Following is the grove_12_chan_touch_sensor_MPR121.py code.
from grove.i2c import Bus
TOUCH_SENSOR_DEFAULT_ADDR = 0x5b
MODE_CONFIG_REG_ADDR = 0x5e
GLOBAL_PARAM_REG_ADDR_L = 0x5c
TOUCH_STATUS_REG_ADDR_L = 0x00
SET_DEBOUNCE_REG_ADDR = 0x5b
FILTERED_DATA_REG_START_ADDR_L = 0x04
CHANNEL_NUM = 12
STOP_MODE = 0
NORMAL_MODE = 0x3c
def __init__(self,bus_num = 1,addr = TOUCH_SENSOR_DEFAULT_ADDR):
self.bus = Bus(bus_num)
self.addr = addr
self.threshold = 0
self.touch_flag = *CHANNEL_NUM
data = [0x23,0x10]
self.threshold = threshold
data_status = self.bus.read_i2c_block_data(self.addr,TOUCH_STATUS_REG_ADDR_L,2)
result_value = 
for i in range(CHANNEL_NUM):
if(sensor_status & (1<<i)):
channel_data = self.bus.read_i2c_block_data(self.addr,FILTERED_DATA_REG_START_ADDR_L+2*i,2)
result_value.append(channel_data | channel_data<<8 )
data = self._check_status_register()
touch_status = data | (data<<8)
touch_result_value = self.get_filtered_touch_data(touch_status)
for i in range(CHANNEL_NUM):
if(touch_result_value[i] < self.threshold ):
touch_result_value[i] = 0
for i in range(CHANNEL_NUM):
if(result[i] != 0):
if(0 == self.touch_flag[i]):
self.touch_flag[i] = 1
print("Channel %d is pressed,value is %d" %(i,result[i]))
if(1 == self.touch_flag[i]):
self.touch_flag[i] = 0
print("Channel %d is released,value is %d" %(i,result[i]))
mpr121 = TouchSensorMpr121()
result = mpr121.listen_sensor_status()
if __name__ == '__main__':
If everything goes well, you will get the result. When you touch the CH0 ~ CH11 pads, it will trigger channel # pressed and Channel # released with corresponding pressure values.
>>> %Run grove_12_chan_touch_sensor_MPR121.py
Channel 8 is pressed, value is 308
Channel 8 is released, value is 0
Channel 9 is pressed, value is 170
Channel 9 is released, value is 0
Channel 10 is pressed, value is 340
Channel 8 is pressed, value is 180
Schematic Online Viewer
[Zip] Grove - 12 Key Capacitive I2C Touch Sensor V2 eagle files
[PDF] Datasheet of MPR121
This is the introduction Video of this product, simple demos, you can have a try.
Leaf Piano: We made a piano using a touch sensor, as well as leaves for piano keys.
Play with Scratch: How to play a scratch game with a Touch Sensor?
Please do not hesitate to submit the issue into our forum.