IWR6843: Synchronization between multiple radar board

Hi,

We will get back to you on exact software changes needed to support this behavior. In the meantime, I would recommend you look at the following thread to ensure you understand the limitations of these pins on the 6843 devices: https://e2e.ti.com/support/sensors-group/sensors/f/sensors-forum/1130150/iwr6843aopevm-daisy-chaining-multiple-radars-through-sync_in-sync_out

Best Regards,
Alec

Hello,

First off I would like to know what 6843 EVM you are using as there are hardware differences in-between them, some require board modifications in order to use the SYNC pins. Second, we do not have any example code specifically with 6843 but within our ROS Driver package we have a document showing how to use 1843 and a TDA4VM (TI EVM) in order to sync multiple sensors. The guide can also be used with other single board computers such as a Raspberry Pi. You can find this guide by cloning the ROS repo (git clone https://git.ti.com/cgit/mmwave_radar/mmwave_ti_ros/) and then opening the MarkDown file located at mmwave_ti_ros/ros_driver/src/ti_mmwave_rospkg/docs/Multi_sensor_time_synchronization.md

Best Regards,

Pedrhom Nafisi

Thanks for your information. I use three custom boards with iwr6843 and one mainboard to control them.

Since there is interference between them, I want to use sync_in and sync_out to synchronize their emitting time.

Hi,

Responses will be delayed until January 3rd because of the holidays. Thank you for your patience.

Best,

Nate 

Hi Nathan and Pedrhom,

 Is there update for this?

 We have read the article that Pedrhom suggested in (git clone https://git.ti.com/cgit/mmwave_radar/mmwave_ti_ros/), and it mentioned about two methods below:

  1). # Software Based Method

  The software based approach is very simple and enables coarse synchronization (1ms) among frames from multiple mmWave devices for a period of time. It works by configuring all sensors, waiting to send the start command to each device until all devices are fully configured. At that point the start command is sent to each device with an optional user defined delay value between subsequent start commands. The delay can be used to offset frames from different radars in time. One of the limitations of this approach is that the triggering of each frame following the first frame, for each sensor, is controlled by that sensor's own clock. Because of slight variations, over a long period of time, the timing of the frames for one device may become out of sync with that of another. 

  We have tried this , and we also suffered the disadvantage as above description that it would be out of sync after a long period of time.

  2). # Hardware Based Method

  **Note**: The hardware sync method applies only when the host machine is TI's [SK-TDA4VM](https://www.ti.com/tool/SK-TDA4VM). It is also assumed that the setup of the Robotics SDK and Docker container is complete. If this has not been completed, follow the instructions [here](https://software-dl.ti.com/jacinto7/esd/robotics-sdk/08_02_00/docs/source/docker/README.html).
  This approach utilizes the GPIO PWM functionality on the SK-TDA4VM to generate a triggering signal. The mmWave devices can be configured for HW Trigger mode which means that each frame is triggered at the rising edge of a pulse signal fed into the SYNC_IN pin. The mmWave devices can also be configured with a trigger delay, which allows for the triggering of frames for multiple radars to be offset from one another. This can be beneficial in reducing the probability of seeing "ghost targets" caused by parallel interference.

  This approach has clear advantages in terms of time synchronization. This is because the triggering of frames for all the connected sensors is controlled by a single source. Also, assuming an equal length for the path of the triggering pulse signal to each sensor, the sensors all receive the signal at the same instant.

  **Note**: HW based synchronization was tested with TI's IWR1843BOOST EVM due to the SYNC_IN pin being accessible without board modification. Modification may be required in order to access the SYNC_IN pin on other EVMs.

  This HW method is what we want to do now.

  But we have to check if sync_in and sync_out are enabled in IWR6843ISK first like the IWR1843BOOST. If these two GPIOs are supported, is there example code of using them? Could you confirm this?

Sincerely.

Hello,

With the IWR6843ISK you will need a board modification, but post modification the functionality will be the exact same. There are many threads on E2E involving hardware triggering with mmWave and I recommend doing a deep dive via google and using "site:e2e.ti.com" as a filter. Unfortunately we do not have any sample code because the functionality/implementation will be different depending on what you are using as a hardware trigger.

Board Modification:

https://e2e.ti.com/support/sensors-group/sensors/f/sensors-forum/750656/iwr6843-sync_in-hardware-trigger

Best Regards,

Pedrhom Nafisi