Matrix - Thermistor

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1 Introduction

Thermistor

• The Matrix-Thermistor module is a thermistor module. It has a 3 pin 2.54mm spacing pin header of which 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.
• To increase measured values' accuracy please make the sensor in close contact with a measured object.

2 Features

• GPIO, 3.3/5V
• 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

• The module mainly contains a thermistor. A thermistor is a type of resistor whose resistance is dependent on temperature.

4 Download Matrix Source Code

All the matrix modules' code samples are open source. They are maintained on GitHub: https://github.com/friendlyarm/matrix.git
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 https://github.com/friendlyarm/matrix.git

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

5 Connect to NanoPi 2

5.1 Hardware Connection

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

Connection Details:

Matrix-Analog_to_Digital_Converter	NanoPi 2
SDA	Pin3
SCL	Pin5
5V	Pin4
GND	Pin6

Matrix-Thermistor
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-Thermistor'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.

5.2 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 https://github.com/friendlyarm/linux-3.4.y.git.

5.3 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-Thermistor module.

$ matrix-adc

Here is what you should expect:

5.4 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);        
        }
        usleep(10000);
    }
    return 0;
}