---

Embedded Devices

The Display is equipped with several embedded devices, which add multiple functionalities. This section describes each of those embedded devices.

Buzzer

The Display comes with a programmable buzzer. It is typically used to sound-notify the user of any system fault or warning. The buzzer can be configured via C++ code or from the terminal.

Enter the following commands to configure the buzzer from the terminal:

$ echo 0 > /sys/class/pwm/pwmchip1/export
$ echo 1000000 > /sys/class/pwm/pwmchip1/pwm0/period
$ echo 500000 > /sys/class/pwm/pwmchip1/pwm0/duty_cycle 
$ echo 1 > /sys/class/pwm/pwmchip1/pwm0/enable // Turn buzzer on
$ echo 0 > /sys/class/pwm/pwmchip1/pwm0/enable // Turn buzzer off

The values are in nano seconds, So 1000000=1msec ==> 1KHz.

Use the following code to configure the buzzer in the Reference App via C++:

io = new digital_io();
io->set_buzzer_freq(frequency)
io->set_buzzer(true);	// Turn buzzer on
io->set_buzzer(false);	// Turn buzzer off

To control the volume of the buzzer from the Reference App, use the slide bar on the right side:

Buzzer Volume Control in the Reference App

If a further frequency and notification sound are required, use the device's audio output, which can play any MP3 or WAV file.

Wi-Fi Module (All-in-one MConn)

In some configurations, the Display comes equipped with an 802.11b/g/n module that can be set up as an Access Point (AP) or a client. By default, the Wi-Fi module is set up as an AP, broadcasting the SSID: MRS-Display-xxx with a passphrase: 12345678.

To switch between AP and Station mode in the Reference App, tap the toggle button on Wi-Fi Settings screen:

Switching Between AP and STA Mode

Access Point Mode

To set the Wi-Fi in the Access Point (AP) mode, follow the steps below:

1. Edit the configuration file for the AP mode:

$ vi /etc/wpa_supplicant.conf

2. Enter the following terminal commands to enable the AP mode:

$ onebox-set-mode ap
$ systemctl restart onebox-protocol@3
$ systemctl restart network-wireless

Now, you will be able to connect a client to the Display.

Station Mode

To set the Wi-Fi in the Station (STA) mode, follow the steps below:

1. Edit the configuration file for the STA mode:

$ vi /etc/sta_settings.conf

2. Enter the following terminal commands to enable the STA mode:

$ onebox-set-mode sta
$ systemctl restart onebox-protocol@3
$ systemctl restart network-wireless

3. Use the command ifconfig to ensure the connection of Display to the Access Point.

Important
Numerous settings can be configured in the config files. For a full datasheet of the Wi-Fi module, contact MRS Electronic.

Radio Tuner (All-in-One Feature)

The Display has a high-performance AM/FM tuner. When the scan for an FM/AM station is made, MConn tunes to the station within the threshold of field strength. The Alsa library in the Reference App controls the selection between audio output from Linux OS and the AM/FM radio tuner. To control it via C++ in the Reference App, use the following code:

//Reference App tuner module
Tuner *tuner = new Tuner();
engine.rootContext()->setContextProperty("tuner", tuner);

To access the radio from the Reference App, navigate to the Radio tab:

Radio Tab in the Reference App

Coprocessor

The MConn Display has a coprocessor that performs multiple functions, including the following:

1. Reads analog inputs.
2. Serves as a watchdog to ensure that the main processor does not lock up.
3. Keeps the main processor alive when the ignition signal goes low, and it can be done by turning on KEEP_ALIVE output on coprocessor. It allows shutting down of the main processor in a delayed and controlled manner.
4. Sends/Receives messages on the CAN bus.
5. Asserts specific commands/data on CAN bus immediately at power on. The main display can take at least 5 seconds to boot. Whereas the coprocessor is instant-on and can perform CAN functions at startup if necessary. Contact MRS Electronic for more details.
6. Holds a CAN bootloader and can be reprogrammed through the CAN bus.

Information
You can update the software on the coprocessor by the **MRS Developers Studio**, which allows you to write the software in C or Graphical Programming. For the source code of the application that currently resides on the Display, contact MRS Electronic.

GPS (All-in-One Feature)

The Display can have a GPS receiver to support concurrent reception of up to 3 GNSS (GPS, Galileo, GLONASS, BeiDou). The GPS receiver provides the display's location using NMEA data (UART interface on the Display) available on the path: /dev/ttymxc1.

Use the QtSerialPort Library to read the GPS data in the Reference App using C++ code:

//Reference App gps module
gps *m_gps = new gps(m_version, &app);
m_gps->start();

To access the GPS information in the Reference App, navigate to the GPS tab:

GPS Tab in the Reference App

Bluetooth (All-in-One Feature)

In some configurations, the Display comes equipped with Bluetooth 4.0 and the BlueZ software. The Bluetooth can be controlled via C++ code and from the terminal.