@dlee ,

Yes the new TOF sensor (IRS2975C) is more powerful that the previous generation. What I mean by that is that it can emit more IR power but also heats up more. Emitting more power allows the sensor detect objects at larger distances or objects that are not as reflective.

In current operating mode, the auto exposure control is enabled inside the sensor itself, which modulates the emitted IR power based on the returns that the sensor is getting. That is to say, the power draw will vary depending on what is in the view of the sensor. If there are obstacles nearby, the output power should be low, otherwise it can be high. At full power, the module can consume close to 0.8-0.9W

So the first solution, if design allows, is to add a heat spreader to dissipate the heat, which you already started experimenting with. The sensor has a large exposed copper pad in the back for heat sinking purposes for this exact reason. Just be careful not to short this pad to anything, use non-conducting (but heat transfering) adhesive pad between the sensor and heat spreader.

In terms of a software solution to the issue, we can query the temperature of the emitter. We can also control the maximum emitted power used by the auto exposure algorithm. That is to say, still leave the auto exposure running in the sensor, but limit the maximum power that it is allowed to use.

We are planning to add some software protection that limits the maximum output power as a function of the emitter temperature. This will require some implementation and testing.

Meanwhile, please consider using a heat spreader, which will be the best solution if you want to make use of the full sensor's operating range and not have our software limit the output power in order to prevent overheating.

Hello @Kashish-Garg-0

we have a curve that is "motor voltage vs rpm", meaning that for a desired RPM, it tells the ESC what average motor voltage should be applied. The average motor voltage is defined as battery_voltage * motor_pmw_duty_cycle. The battery voltage in this curve is in millivolts. Since you are typically controlling the desired RPM, as a user you do not need to worry about what "throttle" or voltage to apply - the ESC does this automatically in order to achieve the desired RPM. this calibration curve is used as a feed-forward term in the RPM controller. The ESC does support an "open loop" type of control where you specify the power from 0 to 100%, which is similar to a standard ESC, but PX4 does not use that ESC control mode.

By the way, you can test the ESC directly (not using PX4) using our voxl-esc tools (https://gitlab.com/voxl-public/voxl-sdk/utilities/voxl-esc/-/tree/master/voxl-esc-tools) which works directly on VOXL2 or a standalone linux PC (or mac). voxl-esc-spin.py has a --power argument where you specify the power from 0 to 100, which translates directly to the average duty cycle applied to the motor.

Here is the calibration for the Starling V2 motor / propeller that we use:
https://gitlab.com/voxl-public/voxl-sdk/utilities/voxl-esc/-/blob/master/voxl-esc-params/mavic_mini_2/mavic_mini_2.xml?ref_type=heads#L63

Also, you can take a look at this post to see how to interpret those parameters a0, a1, a2 : https://forum.modalai.com/topic/2522/esc-calibration/2

We also have some dyno tests for this motor / propeller : https://gitlab.com/voxl-public/flight-core-px4/dyno_data/-/blob/master/data/mavic_mini2_timing_test/mavic_mini2_modal_esc_pusher_7.4V_timing0.csv . We are not sure how accurate that is, but it can be used as a starting point. @James-Strawson can you please confirm that is the correct dyno data for the Starling V2 motors?

Alex

@reber34 , perhaps this approach can work for you:

• record a video encoded at high bit rate (using voxl-camera-server and voxl-record-video . Please note that the output of voxl-record-video will not be in a standard container (such as mp4, etc), but you can fix it with ffpeg : ffmpeg -r 30 -i voxl-record-video.h264 -codec copy videofile.mp4
• re-encode the video offline with desired codecs / bit rates / resolutions
• install gst-rtsp-launch which uses gstreamer to set up an RTSP stream https://github.com/sfalexrog/gst-rtsp-launch/
  • you will first need to figure out what gstreamer pipeline to use on voxl2 that will load your video and parse the h264/h265 frames (can use null sink for testing) and then use that pipeline with gst-rtsp-launch which will take the encoded frames and serve them over rtsp stream.
• gstreamer may be more flexible for tuning the encoding parameters of h264/h265 (compared to voxl-camera-server) and you can also use it in real time later (using voxl-streamer, which uses gstreamer under the hood)

Another alternative is to use voxl-record-raw-image to save raw YUVs coming from voxl-camera-server and then use voxl-replay and voxl-streamer - the latter will accept YUVs from the MPA pipe and encode them using the bit rate that you want. Note that depending on the image resolution, YUV images will take a lot more space than encoded video, but maybe that is also OK since VOXL2 has lots of storage.

Alex

@smilon , voxl-esc-calibrate.py is a script that runs a test procedure in a single motor (with propeller mounted) to calibrate the behavior of the motor / propeller. This procedure only needs to be run once if you change motor or propeller type from a default configuration. The output of this script is just 3 coeficients a1, a2, a3 which you would need to manually enter into an ESC calibration xml file and then upload the xml paramer file to the ESC. Full details about the ESC calibration (when to do it and how) can be found here : https://gitlab.com/voxl-public/voxl-sdk/utilities/voxl-esc/-/blob/master/voxl-esc-tools/calibration.md?ref_type=heads

If you are using standard motors and propellers (one of standard ModalAI drones), you do not need to run this calibration procedure.

It sounds like you got it working, I believe voxl-configre-mpa took care of it. You can see what voxl-configure-mpa typically does here : https://docs.modalai.com/voxl-configure-mpa/ , which includes running voxl-esc to upload the latest firmware and params for a specific vehicle.

@smilon ,

I believe you are correct! Thank you. We will double check this and fix.

Hello @Gicu-Panaghiu,

I am going to assume you are using VOXL1, since you did not specify..

We do have RAW8 and RAW10 support for OV7251. The selection of the format has to be done in several places.

First, you have to select the correct camera driver, specifically..

ls /usr/lib/libmmcamera_ov7251*.so
/usr/lib/libmmcamera_ov7251.so
/usr/lib/libmmcamera_ov7251_8bit.so
/usr/lib/libmmcamera_ov7251_hflip_8bit.so
/usr/lib/libmmcamera_ov7251_rot180_8bit.so
/usr/lib/libmmcamera_ov7251_vflip_8bit.so

there are 5 options and one of them is _8bit.so which means it will natively ouptput 8bit data (all others output 10 bit data).

the driver name, such as ov7251_8bit has to be the sensor name <SensorName>ov7251_8bit</SensorName> in /system/etc/camera/camera_config.xml.

You can check camera_config.xml for what sensor library is used for your OV7251.

When you run voxl-configure-cameras script, it will actually copy one of the default camera_config.xml that are set up for a particular use case, and I believe it will indeed select the 8bit one - this was done to save cpu cycles needed to convert 10bit to 8bit, since majority of the time only 8bit pixels are used.

Now, you mentioned that HAL_PIXEL_FORMAT_RAW10 is passed to the stream config and unfortunately this does not have any effect on what the driver outputs. If the low level driver (e.g. libmmcamera_ov7251_8bit.so) is set up to output RAW8, it will output RAW8 if you request either HAL_PIXEL_FORMAT_RAW8 or HAL_PIXEL_FORMAT_RAW10.

So if you update the camera_config.xml to the 10bit driver and just keep the HAL_PIXEL_FORMAT_RAW10 in the stream config (then sync and reboot), you should be getting a 10 bit RAW image from the camera. But since the camera server is currently expecting 8 bit image, if you just interpret the image as 8 bit, it will appear garbled, so you will need to handle the 10 bit image (decide what you want to do with it) in the camera server.

Hi

If you are looking for more low level functionality and a bit easier to experiment with, you may want to check out https://gitlab.com/voxl-public/utilities/voxl-rtsp/-/tree/dev . This tool is good for testing or running simple scenarios. This tool accepts some commands (like exposure control) via command line, so you could add a simple feature to save an image upon a command line input. Please see README to see how the exposure control input works and code for how it's implemented.

Please make sure that voxl-camera-server is disabled when you run voxl-rtsp.

If you still would like to go through the voxl-camera-server approach, we may need some more input from respective devs :).

I hope this helps..

Alex

The ipk is available here now : http://voxl-packages.modalai.com/stable/voxl-hal3-tof-cam-ros_0.0.5.ipk - you should be able to use the launch file to choose between two modes (5=short range and 9=long range) and fps, which are listed in the launch file.

@Moderator said in VOXL ESC Mini 4-in-1 Current per Motor:

Is it possible to step up voltage?

Can you please clarify the question?

Mini ESC is designed for small drones ( < 500g ). The ESC has been tested to handle 15A continous at 15V input continuously (60+ seconds), but with full direct air flow from propellers. This would simulate a full throttle "punch-out" on a small FPV drone (high current, but also lots of direct airflow = cooling). Do not use this ESC if the drone needs 10-15A per channel just to hover. Use it in application where hover current per motor is less than 5A (ideally 2-3A which is very typical) and absolute maximum continuous current per motor can be 10-15A.

For example, motors used for small FPV drones often are around 1306 size (3-4S Lipo). Those motors are usually rated for up to 10-12A continous (for 30-60 seconds). Larger motors can be used as long as maximum motor current does not exceed 10-15A (still 2-3A at hover) and there is sufficient cooling.

Always check ESC board temperature during initial flights / tuning. Temperature must stay below 110C at all times (critical), typically in the range of 40-70C for most applications. The ESC will most likely fail above 125C.

Temperature of the ESC board is the limiting factor because the board is so small. Mosfets can handle a lot of current as long as they don't overheat. So the design of the drone is very important (either use low current so that temperature is not an issue or properly design air flow from propellers and/or add heat spreader to keep the ESC board temperature in normal range for higher current draw applications).

ESC provides real time temperature feedback and it can be viewed in PX4 / QGC. Additionally, the PX4 logs contain the temperature information.

@Prabhav-Gupta , yes it seems like OpenCV and ROS YUV_NV12 formats do not match up. I will take a look at it.. it seems the ROS YUV is packed (interleaved) while standard for storing YUV NV12 is having two planes : plane 1 : Y (size: widthheight), plane 2 : UV (size: widthheight/2)

In the meantime.. you can stream a rtsp h264/h265 from VOXL (use decent quality so that image looks good) and use opencv to receive the stream and get decompressed images: https://stackoverflow.com/questions/40875846/capturing-rtsp-camera-using-opencv-python

Would that work for you ? (unfortunately with rtsp stream, you will not get the full image metadata, like exposure, gain, timestamp, etc).

RTSP streaming can be done using voxl-streamer, which can accept either a YUV (and encode it) or already encoded h264/5 stream from voxl-camera-server.

Alex

Initial docs are up : https://docs.modalai.com/camera-video/electronic-image-stabilization/

@JP-Drone , If your camera is flipped (rotated 180), you just need to update your extrinsics to tell EIS the orientation of camera w.r.t IMU:

https://gitlab.com/voxl-public/voxl-sdk/services/voxl-camera-server/-/blob/dev/voxl2-eis.md?ref_type=heads#extrinsic-calibration

Instead of right side up

"RPY_parent_to_child":    [0, 90, 90]

your extrinsic file should be

"RPY_parent_to_child":    [0, 90, -90]

In other words, your /etc/modalai/extrinsics.conf should contain the following entry:

{
    "parent": "imu_apps",
    "child":  "<camera_name>",
    "T_child_wrt_parent": [0.0, 0.0, 0.0],
    "RPY_parent_to_child":    [0, 90, -90]
}

(I am assuming VOXL2 is mounted in normal orientation, right side up)

Please try.

Also, we recently merged the EIS feature to dev branch of camera server, still working on better documentation.

Alex

Here are two image samples taking using IMX412 and AR0144. IMX412 is slightly cropped on the sides, but it's also a slightly narrower lens. AR0144 image is without LSC correction. Also images slightly out of focus because the test pattern is very close to the camera. The brightness in the IMX412 image is more evenly distributed (larger, better lens), so the center of the image is not over-exposed, unlike the AR0144. This should be corrected with the proper LSC..

IMX412

AR0144-color

OK, I was able to confirm this configuration:

• VOXL2
• M0173 + 3x AR0144 + 1x IMX412 (C27 config)
• M0155 + 1x AR0144 plugged into J8
  • AR0144 i2c slave id change via resistor
  • small camera driver modification for new slave id
• also verified the synchronization between the 4 AR0144

The resistor swap was relatively easy, but i used a special "tweezer" soldering iron tip. I can be difficult without the right tools.. Let me check if we can do a swap for the custom order..

See the image with marked slave id select resistor that needs to move to a pad right above the current placement. It can be a bit tricky to do it

Alex

Hi @Jordyn-Heil ,

OK, so did some digging. Essentially, the 4x AR0144 + 1x IMX412 would be the same as C27 config (https://docs.modalai.com/voxl2-coax-camera-bundles/#mdk-m0173-1-02) + another AR0144 connected to J8 via M0155 (so that would be J8L, camera slot 4).

There are also some other options like moving IMX412 to J8, but in either case, unfortunately there is a change required in one of the AR0144 to switch the i2c slave address from default. This means moving a resistor on the camera from one pad to another.

I am going to double check this by actually switching the slave ID, but just wanted to give you an update..

Alex

@Jetson-Nano , generally it is not possible to cause a VOXL2 reboot during normal operation. There are a few cases which can cause a kernel panic and the board would reboot into a recovery mode for debugging. This only occurs during testing some experimental features and you would normally not see this behavior. If the board simply reboots and is running again after reboot, it is very likely a power failure.

The power cable, if wiggled a bit, can become temporarily normal again, so it is possible what happened to you. The main issue is that wiggling the power cable, in general, loosens the contacts that make contact with the pins, causing the contact pressure to weaken and contact resistance to increase.

Alex

@tonygurney , please see the doc page regarding GPIO and the offset:

https://docs.modalai.com/voxl2-linux-user-guide/#gpios

specifically,

Starting SDK 1.2.X/System Image 1.7.3, GPIOs are exported by default in /sys/class/gpio, the GPIO have an offest of 1100 (e.g. GPIO 84 = 1184).

One more thing.. Do you need global shutter cameras? or is a small size a requirement? You could use the IMX412 cameras, which are rolling shutter, but much higher resolution and color quality. Have you considered that option?

Alex

@Jordyn-Heil , for ordering, since it's a custom order, please send us a message via http://modalai.com/contact and provide the following part number. We will send you an invoice.

MSU-M0166-2-01

(which includes MCCA-M0166-2 + M10000858 lens (AR0144 Camera Color Coax))

Do you want to wait until I confirm 4x concurrency?

Regarding panoramic stitching, yes obviously lens shading will be an issue, however if you have 4 cameras, you only need 90 degrees of horizontal FOV per camera and the current lens provides 139 degrees of horizontal FOV (https://docs.modalai.com/M0166/). So i think 90 degrees + small overlap won't be too bad (but LSC correction will be required to achieve seamless stitching)
. Also, the VOXL2 GPU can do the stitching, I can help you get started (should be a fun project).

Here is an old example i found of original vs LSC corrected monochrome images:

original:

LSC corrected:

You see the corners are heavily quantized because they were so dark and pixel resolution is not enough. The original RAW image is 8 bit. The AR0144 camera does support 10 and 12 bit output, and the 12 bit data would help a lot with Quantization effects after correction. the 10 and 12 bit stream is experimental and there are some issues (will not go into detail here), that is why we using 8 bit, which is stable.

Alex

@Jetson-Nano , when you view tflite output from voxl-portal, the tflite processing actually starts, which causes a surge in cpu and gpu load, which causes an increased power draw. If the power cable has worn contacts (with increased resistance), the voxl2 board can go in undervoltage condition and reboot. With this in mind, could you please try to replace the power cable and let us know if this solves your issue?

Thank you

Alex