Ixonos sensact library – sensor/actuator communication made easy!

Fresh out of the Ixonos engineering labs comes the embedded HTML5 industrial prototype that Ixonos engineers are working on. The latest version of this prototype samples sensor data from a Texas Instruments multi-function sensor device http://www.ti.com/tool/boostxl-senshub which is connected via USB – this device includes various sensors (thermometer, compass, gyro, pressure, etc.).

To easily access these sensors we have created a library named “libsensact” which abstracts away the communication channel and input/output details of sensor or actuator devices – each device is simply characterized by it's name and the names of sensor/actuator variables that it provides. The communication channel which is abstracted can be any of USB, I2C, UART, Ethernet, EtherCAT, CAN, ProfiNET, etc.. Though, the first version of the library only supports USB.

The library offers simple connection handling functions and get/set functions for retrieving or setting sensor/actuator variable values of various types (char, int, float, etc.).

For example, retrieving the “temperature” and “pressure” values of the multi-function sensor device named “senshub0” is as simple as described by the following application code:

#include <stdio.h>
#include <unistd.h>
#include "sensact.h" 

#define TIMEOUT 100 // ms

int main(void)
{
  int device;
  float temp;
  float pressure;
  int status;

  device = connect("senshub0");

  status = get_float(device, "temperature", &temp, TIMEOUT);
  if (status < 0)
    printf("Error fetching temperature.");
  else
    printf("Sensor Temperature: %f\n", temp);

  status = get_float(device, "pressure", &pressure, TIMEOUT);
  if (status < 0)
    printf("Error fetching pressure.");
  else
    printf("Sensor Pressure: %f\n", pressure);

  disconnect(device);

  return 0;
}

Also, for each sensor/actuator device, the library contains an entry in a device configuration structure list which contains device specific configurations. For example, the “senshub0” device is configured by the following code:

#include "device.h"

/* List of supported sensor/actuator devices */ 

struct device_t device[] = 
{ 
  { .name = "senshub0", 
    .description = "TI Sensor Hub USB device", 
    .connection = USB, 
    .vid = 0x1CBE, 
    .pid = 0x0003, 
    .endpoint = 0x1 }, 
  { } 
}

For different connection types there will be different “.connection” definitions and subsequently different related dot configuration variables.

Future plans for this library are to add support for more connection types and extend the API with subscriber type functionality so that the user can register callback functions which will be called upon value changes for sensor/actuator devices which are able to support event-driven communication.

Watch out for more blog entries on this library as it evolves...

That's it – keep it simple!

Martin Lund, System Architect - Ixonos