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ASCII Communications Example Project

This IS Communications Example project demonstrates binary communications with the
Inertial Sense Products (IMX, uAHRS, and uIMU) using the Inertial Sense SDK. See the
ASCII protocol section for details on the ASCII packet structures.


Project Files

SDK Files


Step 1: Add Includes

// Change these include paths to the correct paths for the project
#include "../../src/ISComm.h"
#include "../../src/serialPortPlatform.h"

Step 2: Initialize and open serial port

    serial_port_t serialPort;

    // Initialize the serial port (Windows, MAC or Linux) - if using an embedded system like Arduino,
    //  you will need to handle the serial port creation, open and reads yourself. In this
    //  case, you do not need to include serialPort.h/.c and serialPortPlatform.h/.c in your project.

    // Open serial, last parameter is a 1 which means a blocking read, you can set as 0 for non-blocking
    // you can change the baudrate to a supported baud rate (IS_BAUDRATE_*), make sure to reboot the IMX
    //  if you are changing baud rates, you only need to do this when you are changing baud rates.
    if (!serialPortOpen(&serialPort, argv[1], IS_BAUDRATE_921600, 1))
        printf("Failed to open serial port on com port %s\r\n", argv[1]);

Step 3: Disable prior message broadcasting

// Stop all broadcasts on the device on all ports.  We don't want binary message coming through while we are doing ASCII
if (!serialPortWriteAscii(&serialPort, "STPB", 4))
    printf("Failed to encode stop broadcasts message\r\n");

Step 4: Enable message broadcasting

    // ASCII protocol is based on NMEA protocol
    // turn on the INS message at a period of 100 milliseconds (10 hz)
    // serialPortWriteAscii takes care of the leading $ character, checksum and ending \r\n newline
    // ASCB message enables ASCII broadcasts
    // ASCB fields: 1:options, 2:PIMU, 3:PPIMU, 4:PINS1, 5:PINS2, 6:PGPSP, 7:reserved, 8:GPGGA, 9:GPGLL, 10:GPGSA, 11:GPRMC
    // options can be 0 for current serial port, 1 for serial 0, 2 for serial 1 or 3 for both serial ports
    // Instead of a 0 for a message, it can be left blank (,,) to not modify the period for that message
    // please see the user manual for additional updates and notes

    // Get PINS1 @ 10Hz on the connected serial port, leave all other broadcasts the same, and save persistent messages.
    const char* asciiMessage = "ASCB,512,,,1000,,,,,,,,,";

    // Get PINS1 @ 50Hz and PGPSP @ 5Hz on the connected serial port, leave all other broadcasts the same
    // const char* asciiMessage = "ASCB,,,,20,,1,,,,,,,";

    // Get PIMU @ 50Hz, GGA @ 5Hz, both serial ports, set all other periods to 0
    //  const char* asciiMessage = "ASCB,3,20,0,0,0,0,0,100,0,0,0,0,0";

    if (!serialPortWriteAscii(&serialPort, asciiMessage, (int)strnlen(asciiMessage, 128)))
        printf("Failed to encode ASCII get INS message\r\n");

Step 5: Save persistent messages

(OPTIONAL) This remembers the current communications and automatically streams data following reboot.

if (!serialPortWriteAscii(&serialPort, "PERS", 4))
    printf("Failed to encode ASCII save persistent message\r\n");

Step 6: Handle received data

    // STEP 4: Handle received data
    unsigned char* asciiData;
    unsigned char asciiLine[512];

    // you can set running to false with some other piece of code to break out of the loop and end the program
    while (running)
        if (serialPortReadAscii(&serialPort, asciiLine, sizeof(asciiLine), &asciiData) > 0)
            printf("%s\n", asciiData);

Compile & Run (Linux/Mac)

  1. Create build directory
    cd InertialSenseSDK/ExampleProjects/Ascii
    mkdir build
  2. Run cmake from within build directory
    cd build
    cmake ..
  3. Compile using make
  4. If necessary, add current user to the "dialout" group in order to read and write to the USB serial communication ports:
    sudo usermod -a -G dialout $USER
    sudo usermod -a -G plugdev $USER
    (reboot computer)
  5. Run executable
    ./ISAsciiExample /dev/ttyUSB0

Compile & Run (Windows MS Visual Studio)

  1. Install and Configure Visual Studio
  2. Open Visual Studio solution file (InertialSenseSDK\ExampleProjects\Ascii\VS_project\ISAsciiExample.sln)
  3. Build (F7)
  4. Run executable
    C:\InertialSenseSDK\ExampleProjects\Ascii\VS_project\Release\ISAsciiExample.exe COM3


This section has covered the basic functionality you need to set up and communicate with Inertial Sense products. If this doesn't cover everything you need, feel free to reach out to us on the Inertial Sense SDK GitHub repository, and we will be happy to help.