Matrix - Potentiometer

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1 Introduction

Potentiometer

• 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

2 Features

• 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

3 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.

4 Applications

The Matrix-Potentiometer module outputs analog signals which can be converted to digital signals through an ADC converter e.g. the Matrix-Analog_to_Digital_Converter module.
For more details about the Matrix-Analog_to_Digital_Converter module refer to wiki:Matrix-Analog_to_Digital_Converter。

4.1 Connect to NanoPi M1

Refer to the following connection diagram to connect the module to the NanoPi M1:

Connection Details:

Matrix-Potentiometer
GND	NanoPi M1 Pin9
5V	NanoPi M1 Pin2
S	Matrix-Analog_to_Digital_Converter A0

4.2 Connect to NanoPi 2

Refer to the following connection diagram to connect the module to the NanoPi 2:

Connection Details:

Matrix-Potentiometer
GND	NanoPi 2 Pin9
5V	NanoPi 2 Pin2
S	Matrix-Analog_to_Digital_Converter A0

4.3 Connect to NanoPi M2 / NanoPi 2 Fire

Refer to the following connection diagram to connect the module to the NanoPi M2/ NanoPi 2 Fire.

Connection Details:

Matrix-Potentiometer
GND	NanoPi M2 Pin9
5V	NanoPi M2 Pin2
S	Matrix-Analog_to_Digital_Converter A0

4.4 Connect to NanoPC-T2

Refer to the following connection diagram to connect the module to the NanoPC-T2:
Matrix-Potentiometer_NanoPC-T2

Connection Details:

Matrix-Potentiometer
GND	NanoPC-T2 USB Host GND
5V	NanoPC-T2 USB Host 5V
S	Matrix-Analog_to_Digital_Converter A0

5 Compile & Run Test Program

Boot your ARM board with Debian and copy the matrix code:

$ apt-get update && apt-get install git
$ git clone https://github.com/friendlyarm/matrix.git

If your cloning is done successfully a "matrix" directory will be generated.

Compile and install Matrix:

$ cd matrix
$ make && make install

Run test program:

$ matrix-adc

Note: this module is not plug and play therefore before running the module please make sure it is connected to an ARM board.
Here is what you should observe:

The channel0 value is 2460

6 Code Sample

This Matrix code sample can work with all the ARM boards mentioned in this module's wiki. The name of this code sample is "matrix-analog_to_digital_converter". Here is its source code:

int main(int argc, char ** argv)
{
    int i = 0;
    int value = 0;
    int channel = 0;
 
    if (boardInit() < 0) {
        printf("Fail to init board\n");
        return -1;
    }
 
    if (argc == 2)
        channel = atoi(argv[1]);
    system("modprobe "DRIVER_MODULE);
    signal(SIGINT, intHandler);
    for (i=0; i<ADC_READ_TIMES; i++) {
        if (pcf8591Read(channel, &value) != -1) {
            printf("The channel%d value is %d\n", channel, value);
        } else {
            printf("Fail to get channel%d value\n", channel);
        }
    }
    system("rmmod "DRIVER_MODULE);
 
    return 0;
}

For more details about this APIs called in this code sample refer to Matrix API reference manual

8 Update Log

8.1 Feb-24-2016

• Added link to the Chinese version

8.2 June-23-2016

• Re-organized and simplified wiki