Matrix - Potentiometer

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  • The Matrix-Potentiometer module is a Potentiometer module. It can be used in audio control, motion control, transducers, computation and etc.
  • 3 Pin 2.54mm spacing pin header, V is supply voltage, G is ground and S is output analog signal. Users can convert output analog signals to digital signals via ADC conversion.
  • Output Voltage: 0 ~ Vcc


  • GPIO
  • Small
  • 2.54mm spacing pin header
  • PCB Dimension(mm): 8 x 24


  • Pin Description:
Pin Description
S Analog GPIO
V Supply Voltage 5V
G Ground

Basic Device Operation

  • A potentiometer is a three-terminal resistor with a sliding or rotating contact that forms an adjustable voltage divider.If only two terminals are used, one end and the wiper, it acts as a variable resistor or rheostat.
  • This module mainly contains a potentiometer where the resistance changes with changes between the contact and one end terminal.

Download Matrix Source Code

All the matrix modules' code samples are open source. They are maintained on GitHub :
Each branch in this hub contains the matrix modules' code samples for a board that the matrix modules can work with.

  • The matrix-nanopi branch contains the matrix modules' code samples for the NanoPi;
  • The matrix-nanopi2 branch contains the matrix modules' code samples for the NanoPi 2;
  • The matrix-tiny4412 branch contains the matrix modules' code samples for the Tiny4412;
  • The matrix-raspberrypi branch contains the matrix modules' code samples for the RaspberryPi

Please follow the steps below to get the source code:
Install the git utility on a PC running Ubuntu14.04

$ sudo apt-get install git

Clone the matrix code from GitHub

$ git clone

If this is successful a "matrix" directory will be generated, which will contain all the matrix modules' code samples.

Connect to NanoPi 2

Hardware Connection

Please refer to the following connection diagram to connect the Matrix-Potentiometer to the NanoPi 2:

Connection Details:

Matrix-Analog_to_Digital_Converter NanoPi 2
SDA Pin3
SCL Pin5
5V Pin4
GND Pin6
GND NanoPi 2 Pin9
5V NanoPi 2 Pin2
S Matrix-Analog_to_Digital_Converter A0

This module's output signals are analog signals. You can use our Matrix-Analog_to_Digital_Converter to convert them to digital signals.
Please connect the Matrix-Analog_to_Digital_Converter to the NanoPi 2 and then connect Pin S of the Matrix-Photoresistor's pin header to Matrix-Analog_to_Digital_Converter's A0.
For more details about the Matrix-Analog_to_Digital_Converter module please refer to wiki: Matrix_-_Analog_to_Digital_Converter.

Compile Test Program

Please login the matrix hub and enter the nanopi2 branch

$ cd matrix
$ git checkout nanopi2

Compile the Matrix code

$ make CROSS_COMPILE=arm-linux- clean
$ make CROSS_COMPILE=arm-linux-
$ make CROSS_COMPILE=arm-linux- install

Note: please make sure to install the cross compiler "arm-linux-gcc-4.9.3" on your PC, which is used to compile files for the NanoPi 2.
Generated library files are under the "install/lib" directory. The test program is under the "install/usr/bin" directory. Its test program is "matrix-adc".
The modules are under the "modules" directory. Its driver's source code is in

Run Test Program

Please insert a TF card which is flashed with Debian to a Linux host and mount its boot and rootfs sections.
We assume the rootfs is mounted to /media/rootfs then please run the following commands to copy the driver, library and test program to the card.

$ cp modules /media/rootfs/ -r
$ cp install/lib/* /media/rootfs/lib/ -d
$ cp install/usr/bin/* /media/rootfs/usr/bin/

Insert this TF card to your NanoPi 2, power on and run the following commands to load the driver.

$ cd /modules
$ insmod pcf8591.ko

Please run the following command to test the Matrix-Potentiometer module.

$ matrix-adc

Here is what you should expect:

Code Sample

int main(int argc, char ** argv)
    int i = 0;
    int value = 0;
    int channel = 0;

    if (argc == 2) {
        channel = atoi(argv[1]);
    for (i=0; i<ADC_READ_TIMES; i++) {
        if (pcf8591Read(channel, &value) != -1) {
            printf("channel%d value=%d\n", channel, value);
        } else {
            printf("Fail to get channel%d value\n", channel);        
    return 0;