ESC32 Q&A

[Manu]

Pixhawk outputs @400Hz:
Idle 1042-1043us
Armed: 1110us (or above)
max: 1950us

Esc32 config:
PWM_HI_VALUE 1950
PWM_LO_VALUE 1042
PWM_MIN_START 1100
PWM_MIN_VALUE 900
PWM_RPM_SCALE 5200

I am a bit concerned about what will happen if temperature changes if we need to get absolutely same PWM timings between autopilot and ESC. Changing PWM_LO_VALUE 1042 to something lower make ESCs never get the solid green led fixed, which I find very disturbing. Is there a way to check the source code?

I also removed the safety switch on the pixhawk which cut PWM signal to the esc in order to be sure that we always send something to the ESCs. I had some strange startups when using antispark plugs, maybe it could be useful to delay the initialization of ESCs to be sure that autopilot was powered before?

[Manu]

Ok, so I increased PWM_LO_VALUE to 1045 and now it is ok. ESC cannot start if throttle is above PWM_LO_Value. I was expecting a sort of deadzone between PWM_LO_Value and _Min_Start, and do not exactly understand the purpose of PWM_Min_Valid if PWM_LO_Value overrides it.

1042 vs 1045us is less than 0.3% change, I would not expect PWM settings to be so tight...

One other point regarding Close vs Open Loop. I made a calibration with success and it seems ok on my thurst stand.

ESC32_v3.3.1_cal_R2V_15A.pdf

(389.37 KiB) Downloaded 1015 times

Then, in my office I removed props to check every motor/esc direction and verify PWM inputs (read above ). Without props of course Close Loop is off, but it make ESC fall into error (red blinks, bad motor behaviour). This close loop mode looks sexy but more details on what will go on in flight could make users more confident


Last point: current measurement offset. This is a very nice thing, and I believe that hardware is good. However when ESC is running at low loads, I see negative current compared to the 0.00A at initialization with motors stopped. It is a bit weird and not a big issue but maybe it can be corrected in firmware (dunno the hardware schematics, but maybe a voltage drop somewhere). If it helps, jumper is set to Vbat.

As you can see, Vbat is sensed at 28.68V which is far from 24.2V. Other ESC readings: 24.1V - 24.23 - 24.35V.

My 2 cents

[Manu]

Any comment to this? Is there something wrong with voltage readings, a resistor to check somewhere maybe?

[TobyOctane]

Hiho,

I am Tobias Schwering from High Octane Motorsports (http://www.octanes.de). We are building a racecar each year for the Formula Student competition and use a quite elaborated CAN bus system with distributed nodes.
As weight is crucial in this competition, we use RC motors in our cooling system for 3 years now and switched to a fitting propeller last year. But so far we need a selfdesigned controller to convert CAN messages to the PWM signals the standard ESC needs. To eliminate this one (again, it weighs something!) we would like to use the ESC32.
But as our system is far simpler than a multicopter, the fan power should only be controlled by the coolant temperature. So your complex CAN protocol is actually far too much. So we would like to reduce it to its basics, would it be possible to give us some access to the code of a v3? Or are there still some v2 left?
And in case we have to use the closed source v3, are the messages the same as in the github code available?

[aBUGSworstnightmare]

[TobyOctane]

[rput]

Hi,

I have a quick question: Is it possible to control the ESC32 using pwm, yet still read out RPM info from CAN at the same time?

[rput]

anyone?

[sandmen]

no. It's not possible.

[rput]

ok, thanks