VOXL 2 IO - 8 PWM channels & Futaba (SBUS) Rx
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@Alex-Kushleyev Ahh I only have the FCv2. I have a quick linux machine to work with and planned to do this work either on that or the voxl2. I guess my ultimate goal is to have the ability for PX4 to use esc's in the actuators tab bidirectionally. I am wondering how I would make the change to have the M0064 output dshot permanently after verifying test commands so px4 can control the motors to operate in two directions using my 4in1 dshot supported ESC.
I seen an alternative solution here where two voxl-esc's can be wired in parallel together but just using separate ID's to get 8 channels. Wold these ESC's also support bi-directional operation in PX4? It would be a decent cost to implement these so I am hoping my current setup can work but if it proves too difficult to get working I might consider if these are more plug and play.
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@Gary-Holmgren , can you help me understand your set up better? Are you already using a ModalAI esc with 4 outputs and want to add another 4? Is the reason for going to dshot due to the fact that ModalAI esc does not support 8 outputs?
By the way, ModalAI esc does have support for changing direction in real time, but i am not sure if PX4 has this ability to command negative rpms (mainly, the mixer would need to do that).
Alex
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@Alex-Kushleyev Yes of course, I am trying to experiment with ground vehicles but in order for proper operation the motors need to reverse direction for forward and reverse driving. I dont have a modalai in my setup. I wanted to have 4 channels of dshot so my motors could allow for forward and reverse operation, and since the other 4 PWM are still available on the M0064, I could use them for other servo/actuators. I am trying to understand how others may have configured the UGV or rover options using voxl2/ESC combos but have had no luck in having a working setup.
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@Alex-Kushleyev Im starting to think the problem may be my 4in1 ESC I have chosen to power the motors as its meant for drone motors not drive motors. Although I dont see why it wouldn't work since turtlemode allows you to reverse motor direction on demand. I guess I dont know what PX4 expects for an ESC of that vehicle type as there is no documentation I could find on what ESC to use.
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Is your ground vehicle a direct drive BLDC (or do you have a gear box?). Direct drive motors usually require FOC control because wheels typically spin much slower than drone propellers and you need frequent start / stop and high torque / low speed operation.
Do you have an ESC that uses FOC control with dshot input?
Non-FOC control would work if you have a gearbox, but there may still be some jittering at very low RPM.
Alex
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@Alex-Kushleyev Yes it does have a gearbox, and good to know I considered using FOC for avoiding it but I needed quite a bit of torque.
This is the ESC im currently using as it supports PWM/dshot/etc but its just a basic 4in1 meant for flight so I am not sure if I can confugure it to otput bidirectionally ex: 1500uS is zero 1050 is full reverse and 1950 is full forward.
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@Gary-Holmgren, do you have any ModalAI ESCs? If so, which one? I can help you test it with a geared BLDC motor.
Alex
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@Alex-Kushleyev Unfortunately I do not have one, but if that is the only solution here I would think about getting one.
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@Gary-Holmgren , since you already have the IO board M0065 and the Tmotor ESC, you can try the M0065 approach. I will follow up in a few days.
Meanwhile please make sure that you can communicate to VOXL IO (M0065) board from your Linux PC or VOXL2 using
voxl-esctools. You should be able to runvoxl-esc-scan.pyand the board will be detected (if using VOXL2, you can plug M0065 into the 4-pin ESC port) J18 : https://docs.modalai.com/voxl2-connectors/#j18-uart-escvoxl-esc tools: https://gitlab.com/voxl-public/voxl-sdk/utilities/voxl-esc (they are also shipped with the SDK, you can find it in /usr/share/modalai/voxl-esc-tools/)
Alex
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I was just thinking that another option for you is to get a standard reversible ESC that is designed for RC race cars - those ESCs support reversing. I am assuming 1500us pwm signal is neutral , 2000us full forward, 1000us full reverse.
You would need 4 of those and should be able to use PX4 standard PWM output.
It is probably best to use ESCs designed for RC cars, so they are tuned for robust start-up, etc. Those ESCs also often come with their own fans for cooling, since you don't have propellers blowing air over the ESC.
For example, you can even buy a motor with integrated ESC : https://www.losi.com/product/tazer-twin-2-in1-3000kv-brushless-motor-45a-esc-combo-2s-ec3/DYNS1450.html . I have not tried it, but i do have a race car with a Tazer ESC, which is reversible and is controlled by a standard Spektrum receiver.
Alex
