ModalAI Forum

Hi @greg We have not investigated or researched that image sensor.
I do not know of any plans for us to officially support it at this point.
Sorry if this is not what you wanted to hear.

Hi,
This post is quite old now, so going to mark it as resolved. If it is not, please start a new topic in the correct category for your needs.
Thanks!

Hi @noah-heinen,

Thanks for the very detailed write-up and troubleshooting. There is a lot of useful information here, and this is a tough challenge. I hope we can help get it resolved with you.

The first thing that stands out to us is the custom extended-length USB harness between the Doodle Labs radio and VOXL 2 Mini. Before digging further into software, ESC firmware, or platform parameters, I would focus on that physical USB connection.

USB 2.0 High Speed is sensitive to cable construction and signal integrity. Extending the MCBL-00080 interface using discrete, untwisted, unshielded JST-GH conductors is not equivalent to extending it with a properly constructed USB cable. The added length also increases susceptibility to both radiated and common-mode noise, particularly in an electrically noisy environment such as a high-current multirotor.

We should also acknowledge that our standard development cables are not necessarily optimized for the highest-noise or final-production UAS environments. They are primarily intended to help get systems connected and operating during development. For final aircraft integrations, we generally encourage additional cable optimization where appropriate, including shielding, ruggedization, strain relief, and dedicated cable routing or cable channels that keep sensitive interfaces away from high-current and high-noise paths.

We have seen USB stability issues on aircraft when cabling and routing are not ideal, especially around ESCs, motors, and high-current battery wiring. The fact that your disconnects correlate strongly with motor current transients rather than steady-state current makes the custom USB harness and associated grounding/noise coupling particularly worth investigating.

I would recommend addressing the USB harness first:

Keep D+ and D- as a tightly coupled twisted pair and keep the run as short as practical.
Use a shielded USB-rated cable rather than individual discrete wires for the extended portion.
Adding shielding is absolutely a good approach here. Ideally, use the cable shield as a shield rather than simply adding another signal-ground conductor.
Keep the USB harness physically separated from ESC phase wiring, battery leads, and other high dI/dt paths.
Your plan to improve the ground path and experiment with ferrites is also reasonable, although I would first correct the basic USB cable construction before trying to solve the problem primarily with ferrites.

I would not assume there is a specific maximum J3 cable length where it suddenly becomes unreliable. Cable construction, impedance, routing, grounding, and the surrounding EMI environment all matter. A longer run made from discrete untwisted/unshielded conductors is certainly more susceptible than the stock harness, and yes, it could plausibly produce the transient-induced disconnect behavior you are seeing.

Moving the ESC bulk capacitor to the recommended location is also important, particularly on 6S, and I would still make that change. The improvement you observed when powering VOXL from a bench supply is another useful indication that conducted or common-mode noise may be contributing. There may be more than one coupling path here.

However, given the custom extended USB cable construction, I would correct that first and repeat your 0 -> 65% actuator transient test. That is actually a very good controlled reproduction test.

Hi @dvz
It sounds like that specific unit may need to be RMA'd and we can give it a full check-out through our tests.
Please refer to this page for submitting an RMA, as there is not much we can do remotely given your assessments and noted behaviors.
https://www.modalai.com/pages/rma

Hi @qubotics-admin ,
Unfortunately no. ADB is only available on the primary USB-C port. However, SSH options exist to access a console and issue commands and get status of your VOXL.
You can use this post to help guide you with an SSH connection: https://forum.modalai.com/topic/2798/ssh-into-voxl
Hope this helps!

Thanks for responding, and if that board should have any other issues, refer to this post in an RMA where we will waive the removal of the IMU from consideration of other failures.
Thanks!

Hi,
This post is quite old now, so going to mark it as resolved. If it is not, please start a new topic in the correct category for your needs.
Thanks!

Hi,
This post is quite old now, so going to mark it as resolved. If it is not, please start a new topic in the correct category for your needs.
Thanks!

Hi,
This post is quite old now, so going to mark it as resolved. If it is not, please start a new topic in the correct category for your needs.
Thanks!

Hi,
This post is quite old now, so going to mark it as resolved. If it is not, please start a new topic in the correct category for your needs.
Thanks!

Hi,
This post is quite old now, so going to mark it as resolved. If it is not, please start a new topic in the correct category for your needs.
Thanks!

Hi,
This post is quite old now, so going to mark it as resolved. If it is not, please start a new topic in the correct category for your needs.
Thanks!

Hi,
This post is quite old now, so going to mark it as resolved. If it is not, please start a new topic in the correct category for your needs.
Thanks!

Hi @saegsali
yes, I can help with this. Sorry for the delay in responding here...
I will email you to enable the schematic transfer and review setup.
For your schematic, these items will ensure a speedy and seamless review:

• Searchable PDF
• All items annotated and page numbers correct
• Off page references if multi-page
• Caps and R's should have their ratings visible (voltages, power, values)
• A simple block diagram to help me understand what you are trying to do.

Thanks!

Hi @moderator
The operating range is 2-6S input VBAT.
We currently have no plans for >6S at this time on the ESCs.

The 40V is a part rating which gives margin for safe operating limits, transient immunity, or other electrical effects. This is documented to instill confidence in our users that we selected quality parts capable of handling various conditions outside of nominal such as back-EMF, energy dumps, incorrect wiring, or severe transients.

We are keeping tabs on the trends in this market and will ascertain for future products if increased operating points are warranted broadly. I do see up to 8S is becoming more popular, but it will increase size and cost of products to enable that capability.
Thanks!

Hi @rowan-dempster
Yes, we know we purposely put the SPI3 bus in two locations. It was intentional, but we have since learned not the best approach for all customers, so we have no plans to do that again. The CS_N issue you are seeing is not surprising.
That being said, if you keep continuing with the SW configuration (which may not be easily solved and I do not think we've done that internally yet) our only suggestion for options right now are as follows:

• Use a different SPI bus. J3/J5 have other options. It is a smaller "Ask" to enable SPI11 on J5 than fix SPI3.
  https://docs.modalai.com/voxl2-qups/

• Rework (i.e,: remove) the IMU (does not help if you need that IMU however). We can give you a waiver on the RMA exclusions on these boards should something else arise not related to that rework process.

Hope that helps, and sorry if it's not the news you were hoping for.

Hi @gerhold-ten-voorde
Yes, you are correct. Pin 56 is the signal "FORCE_USB_BOOT". It is default weakly pulled down by the SoC.
To enter eDL/QDL mode, this switch connects a 2-2.2K pullup to VREG_S4A_1P8 (J3 pin 47).
So, on M0154, the default OPEN/OFF position does noting, when ON it enables the pullup.
Hope that helps.
Thanks!
Vinny

Hi @jetson-nano I'm not sure I am following.
The ADB Debug port is still available on VOXL 2 when you use an M0062 Debug Board with USB Hub.
Our plug-in boards that connect to J3 and J5 do not consume the primary USB.
See here for guidance: https://docs.modalai.com/expansion-design-guide/#usb-expansion-over-j3--j5

Hi @jetson-nano
Yes, the M0062 debug board provides a USB Hub for these types of use cases.

However, be aware that the VBUS support on that platform is only 1A and may not cover all Doodle TX power modes.
Please see this note: https://docs.modalai.com/cable-datasheets/#mcbl-00085

Hi @dakota_ltu Under an NDA we could consider the ESC. However, even under NDA, we cannot share the VOXL 2 Schematics unless the recipient is also a Qualcomm licensee with their own NDA with Qualcomm.
If that is still a path with value to you, please use this form: https://www.modalai.com/pages/contact-us