Position Feedback Service Demo

The purpose of this app is showing the use of the Position Feedback Module. For that, it implements a simple app that starts the Position Feedback Service with two sensors and shows over XScope the velocity and position and other info. There are also commands to change the sensor type and restart the service.

The data displayed over XScope is:
  • Position 1: the position of sensor 1
  • Angle 1: the electrical angle of sensor 1
  • Velocity 1: the velocity of sensor 1
  • Position 2: the position of sensor 2
  • Angle 2: the electrical angle of sensor 2
  • Velocity 2: the velocity of sensor 2
  • Position Shared Memory: the position from the shared memory, the one used for motion control
  • Position additional Shared Memory: the additional position from the shared memory, the one use for display only
  • Angle Shared Memory: the electrical angle from the shared memory, used for commutation
  • Velocity Shared Memory: the velocity from the shared memory
  • GPIO 0: the value of the GPIO port 0

This app has a console interface to send commands to demonstrate how to change sensors at run time.

The commands are:
  • a [number]: set first sensor type
  • b [number]: set second sensor type
  • ar [number]: set first sensor resolution (ticks per turn)
  • av [number]: set first sensor velocity compute period in microseconds
  • ap [number]: set first sensor port number (1 or 2)
  • (same commands with ‘b’ for sensor 2)
  • e: exit and restart the position feedback service

The new sensor types are taken into account when the service is restarted

  • Min. Nr. of cores: 4
  • Min. Nr. of tiles: 2

Quick How-to

  1. Assemble your SOMANET device.
  2. Wire up your device. Check how at your specific hardware documentation. Connect your sensor, power supply cable, and XTAG. Power up!
  3. Set up your XMOS development tools.
  4. Download and import in your workspace the SOMANET Motor Control Library and its dependencies.
  5. Open the main.xc within the app. Include the board-support file according to your device. Also set the appropriate target in your Makefile.


Make sure the SOMANET Motor Control Library supports your SOMANET device. For that, check the Hardware compatibility section of the library.

  1. Again in your main.xc, set the configuration for the Position feedback Service and you sensor.

    The default configuration sets all parameters using defines from sensor_config.h. You can edit this file or change the values directly in the main.xc.

    You can change the sensor types for the sensor 1 and 2 by changing position_feedback_config_1.sensor_type and position_feedback_config_2.sensor_type. Don’t forget to also set the correponding resolution and velocity_compute_period. Those can also be changed at run time.

    on tile[IFM_TILE]:
    /* Position feedback service */
        //set default parameters
        PositionFeedbackConfig position_feedback_config_1;
        position_feedback_config_1.polarity    = NORMAL_POLARITY;
        position_feedback_config_1.pole_pairs  = POLE_PAIRS;
        position_feedback_config_1.ifm_usec    = IFM_TILE_USEC;
        position_feedback_config_1.max_ticks   = SENSOR_MAX_TICKS;
        position_feedback_config_1.offset      = 0;
        position_feedback_config_1.biss_config.multiturn_resolution = BISS_MULTITURN_RESOLUTION;
        position_feedback_config_1.biss_config.filling_bits = BISS_FILLING_BITS;
        position_feedback_config_1.biss_config.crc_poly = BISS_CRC_POLY;
        position_feedback_config_1.biss_config.clock_frequency = BISS_CLOCK_FREQUENCY;
        position_feedback_config_1.biss_config.timeout = BISS_TIMEOUT;
        position_feedback_config_1.biss_config.busy = BISS_BUSY;
        position_feedback_config_1.biss_config.clock_port_config = BISS_CLOCK_PORT;
        position_feedback_config_1.biss_config.data_port_number = BISS_DATA_PORT_NUMBER;
        position_feedback_config_1.rem_16mt_config.filter = REM_16MT_FILTER;
        position_feedback_config_1.rem_14_config.hysteresis     = REM_14_SENSOR_HYSTERESIS ;
        position_feedback_config_1.rem_14_config.noise_setting  = REM_14_SENSOR_NOISE;
        position_feedback_config_1.rem_14_config.dyn_angle_comp = REM_14_SENSOR_DAE;
        position_feedback_config_1.rem_14_config.abi_resolution = REM_14_SENSOR_ABI_RES;
        position_feedback_config_1.qei_config.index_type  = QEI_SENSOR_INDEX_TYPE;
        position_feedback_config_1.qei_config.signal_type = QEI_SENSOR_SIGNAL_TYPE;
        position_feedback_config_1.qei_config.port_number = QEI_SENSOR_PORT_NUMBER;
        position_feedback_config_1.hall_config.port_number = HALL_SENSOR_PORT_NUMBER;
        position_feedback_config_1.gpio_config[0] = GPIO_INPUT_PULLDOWN;
        position_feedback_config_1.gpio_config[1] = GPIO_OUTPUT;
        position_feedback_config_1.gpio_config[2] = GPIO_OUTPUT;
        position_feedback_config_1.gpio_config[3] = GPIO_OUTPUT;
        PositionFeedbackConfig position_feedback_config_2;
        position_feedback_config_2 = position_feedback_config_1;
        //set sensor 1 parameters
        position_feedback_config_1.sensor_type = HALL_SENSOR;
        position_feedback_config_1.resolution  = HALL_SENSOR_RESOLUTION;
        position_feedback_config_1.velocity_compute_period = HALL_SENSOR_VELOCITY_COMPUTE_PERIOD;
        position_feedback_config_1.sensor_function = SENSOR_FUNCTION_COMMUTATION_AND_MOTION_CONTROL;
        //set sensor 1 parameters
        position_feedback_config_2.sensor_type = QEI_SENSOR;
        position_feedback_config_2.resolution  = QEI_SENSOR_RESOLUTION;
        position_feedback_config_2.velocity_compute_period = QEI_SENSOR_VELOCITY_COMPUTE_PERIOD;
        position_feedback_config_2.sensor_function = SENSOR_FUNCTION_FEEDBACK_ONLY;
        position_feedback_service(qei_hall_port_1, qei_hall_port_2, hall_enc_select_port, spi_ports, gpio_port_0, gpio_port_1, gpio_port_2, gpio_port_3,
                position_feedback_config_1, i_shared_memory[0], i_position_feedback_1,
                position_feedback_config_2, i_shared_memory[1], i_position_feedback_2);
  2. Run the application enabling XScope.

See also

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