Reading Accelerometer Data

1

Hello,

I am having difficulty understanding why I cannot read the accelerometer and/or gyroscope data from my pixhawk. I am using the following code to do so.

int accel_sub = orb_subscribe(ORB_ID(sensor_accel));
struct sensor_accel_s accel;
orb_copy(ORB_ID(sensor_accel), accel_sub, &accel);

If anybody can point out why this is not working, I would greatly appreciate it. I have tried doing this by polling as well. Something like:

/* polling setup */
struct pollfd fds[1] = {};
fds[0].fd = accel_sub;
fds[0].events = POLLIN;

/* check if we have rc input */
int ret = poll(fds,sizeof(fds)/sizeof(fds[0]),500);

if (ret == 0) {
    /* nothing changed */
} else if (ret < 0) {
    /* this is bad */
    warn("error reading rc input");
} else {
    orb_copy(ORB_ID(sensor_accel), accel_sub, &accel);
}

I’m really scratching my head on this one because I can read the “input_rc” topic this way, but not the sensor_accel. When I print out the accelerometer data, it returns all zeros. The same code was applied to the sensor_gyro topic as well.

Thanks,
Jon

2

After further investigation, it appears that the accelerometer and gyro drivers failed to start. I went through this and ran the commands listed there: ls /dev and sensors status. Here is the output from those:

nsh> ls /dev
/dev:
 console
 led0
 mmcsd0
 mtdblock0
 mtdblock1
 null
 pipe0
 pipe1
 pwm_output0
 pwm_output1
 px4fmu
 px4io
 ram0
 rgbled0
 tone_alarm0
 ttyACM0
 ttyS0
 ttyS1
 ttyS2
 ttyS3
 ttyS4
 ttyS5
 ttyS6
nsh>

and

nsh> sensors status
INFO  [sensors] gyro status:
INFO  [lib__ecl] validator: best: -1, prev best: -1, failsafe: NO (0 events)
INFO  [sensors] accel status:
INFO  [lib__ecl] validator: best: -1, prev best: -1, failsafe: NO (0 events)
INFO  [sensors] mag status:
INFO  [lib__ecl] validator: best: -1, prev best: -1, failsafe: NO (0 events)
INFO  [sensors] baro status:
INFO  [lib__ecl] validator: best: -1, prev best: -1, failsafe: NO (0 events)
INFO  [sensors] Temperature Compensation:
INFO  [sensors]  gyro: enabled: 0
INFO  [sensors]  accel: enabled: 0
INFO  [sensors]  baro: enabled: 0
INFO  [sensors] Airspeed status:
INFO  [lib__ecl] 	no data

It seems that the accelerometer and gyroscope drivers are not being started. I tried sensors stop and restarted the driver with sensors start, but the results were the same. Any ideas?

Thanks,
Jon

3

For anybody that may be interested or run into this, I found out that I had set the SYS_HITL parameter to 1 enabling Hardware In The Loop which seemed to disable the sensors. When I turned this off, I was able to read the accelerometer and gyro values.

4

I am the same problem. But just with sensor baro.

pixErro
pixErro872×521 108 KB
. Can someone help me ?