Matrix - Ball Rolling Switch

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1 Introduction

BAll Rolling Switch

• The Matrix-Ball_Rolling_Switch module is a ball switch. Its electrical characteristics are very similar to a mercury switch's however a mercury switch is easily broken, oxidized, leaking and not environment-friendly. This ball switch prevents all these issues.
• The switch is free to move any angle and if that angle is between 15 degrees and 45 degrees a signal will be generated and used as an input to a Schmitt trigger.

2 Features

• GPIO
• Small
• 2.54 mm spacing pin header
• PCB Dimension(mm):16 x 16

• Pin Description:

Pin	Description
S	Digital GPIO
V	Supply Voltage 5V
G	Ground

3 Basic Device Operation

Please connect Pin V to a power supply, Pin G grounded and Pin S to a digital output. When you move the switch pushing the internal metal ball to connect the trigger point a high level signal will be generated and output to a Schmitt trigger which reverses this signal to output a low level signal. When you move the switch pushing the internal metal ball away from the trigger point a low level signal will be generated and output to a Schmitt trigger which reverses this signal to output a high level signal.

4 Applications

4.1 Connect to NanoPi M1

Please refer to the following connection diagram to connect the module to the NanoPi M1:

Connection Details:

Matrix-Ball_Rolling_Switch	NanoPi M1
S	Pin7
V	Pin4
G	Pin6

4.2 Connect to NanoPi 2

Please refer to the following connection diagram to connect the module to the NanoPi 2:

Connection Details:

Matrix-Ball_Rolling_Switch	NanoPi 2
S	Pin7
V	Pin4
G	Pin6

4.3 Connect to NanoPi M2 / NanoPi 2 Fire

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

Connection Details:

Matrix-Ball_Rolling_Switch	NanoPi M2
S	Pin7
V	Pin4
G	Pin6

4.4 Connect to NanoPC-T2

Please refer to the following connection diagram to connect the module to the NanoPC-T2:
Matrix-Ball_Rolling_Switch_NanoPC-T2

Connection Details:

Matrix-Ball_Rolling_Switch	NanoPC-T2
S	Pin15
V	Pin29
G	Pin30

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-gpio_int

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:

Waiting event...
Device[0] value is 1

When you tilt the module, roll the ball and make it touch the trigger point you will see an event is detected.

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-gpio_int". Here is its source code:

int main(int argc, char ** argv)
{
    int i, board;
    int retSize = -1;
    char value[ARRAY_SIZE(dev)];
 
    if ((board = boardInit()) < 0)
        printf("Fail to init board\n");
 
    if (argc == 2) {
        dev[0].pin = atoi(argv[1]);
    }
    printf("Using GPIO_PIN(%d)\n", dev[0].pin);
    system("modprobe "DRIVER_MODULE);
    signal(SIGINT, intHandler);
    if (board == BOARD_NANOPI_T2)
        dev[0].pin = GPIO_PIN(15);
    if ((devFD =sensorInit(dev, ARRAY_SIZE(dev))) == -1) {
        printf("Fail to init sensor\n");
        return -1;
    }
    printf("Waiting event...\n");
    if ((retSize = sensorRead(devFD, value, ARRAY_SIZE(dev))) == -1) {
        printf("Fail to read sensors\n");
    }
    if (retSize > 0) {
        i = 0;
        for (i=0; i<retSize; i++) {
            printf("dev[%d] value: %d\n", i, value[i]);
        }
    }
    sensorDeinit(devFD);
    system("rmmod "DRIVER_MODULE);
    return 0;
}

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

7 Resources

• [Schematic](Matrix - Ball Rolling Switch-Schematic.pdf)

8 Update Log

8.1 Feb-24-2016

• Added the driver's source code location in Section 5.2

8.2 June-17-2016

• Re-organized and simplified wiki