1. Try 1kHz < f < 5kHz, 2, 1N4148 is signal guy, not Schottky. 3. 519 is OK. I like it. 4. BLDC is easy to fry: electronics.stackexchange.com/questions/514793/…. Good luck.

Thank @tlfong01 I will try the 5819 first then.

also what about Zener Diode. Are they any good in this scenario ?

@Joan thanks , please see the question I just added the circuit diagram with a bit of description. Hope the basics are right :)

@ZAK: (1) Zener is to get a stabilized reference voltage, eg in regulated power supply. (2) You might find the following useful: Back EMF Flyback Diode Selection Notes - rpi forum 2019ja17 forums.raspberrypi.com/…

One more thing - I don't know anything about DShot ESC. So my suggestions might be silly. What is DShot ESC Protocol? - 2016nov08 oscarliang.com/dshot

Thanks @tlfong01 so its means they wont work for me. Thanks

@joan PICO is only connected to ESC and RPI and only ESC got that much power to fry a PICO so the main point of investigation atm. DSHOT protocol is digital protocol to replace old analog ones. Mainly concerned with how to pass data from MCU to an ESC. Where DShot (ESC) got its own MCU to interpret the input and forward it to motors. So the protocol in itself has nothing to do with my problem.

@tlfong01 looking at the diagram do you think putting a diode btween PICO and ESC will solve my problem? like in case voltage is flowing towards the pico then will stop it and also not affect the outward frequency ? My main question here is Diode can pass KHz of frequency without rectifying (changing/distorting) it towards ESC ?

@joan so if I understand you are saying I dont need Diodes ? The strange thing is, sometimes it works properly even with 4 motors and always works with 2 motors. So I thought it might be because 4 motors pushing back more voltage towards PICO and frying it. However if you think I need diodes could you suggest the part number ? thanks

@tlfong01 tested 1N5819 they dont work...seems blocking the whole signal from PICO to ESC.

A coouple of questions: (1) BLDC motor usually has one than one input signal. So yours don't seem to be BLDC, but just DC motor. (2) You battery might only be strong enough to drive two motor and not more. (3) Flyback diodes usually connect to motor side, no input signal side.

@tlfong01 (1) I didn't show in the diagram but each motor is connected to ESC using 3 wires. so they are BLDC (2) It can be a reason however it works sometimes, which makes things worse to solve the problem (4) Make sense, however it will keep the ESC safe from motors but not sure if PICO is affected by ESC leaking and not directly from motors. Like if ESC decides to stop / reduce the voltage to reduce the speed then the riffle effect of the voltage goes to the PICO ? T

The interesting thing is....I removed all the Diodes and its working fine now (again). But still want to know the reason behind as it makes the whole system unpredictable. I say its working fine because before frying PICO one of the motor gets desync (vibrate/gets noisy or doesn't run at all), which it is not doing atm.

@ZAK: (1) So your one wire is in fact three wires. (2) Perhaps you can give us the links to your ESC and BLDC motor.

@tlfong01 no sorry, there are 3 wires to each motor from ESC to a motor. links for ESC and motors are hobbywing.com/goods.php?id=653 or aliexpress.com/item/… and motors aliexpress.com/item/…

and I am using a 4 cell Lipo battery with upto 16v .

Many thanks for the links: (1) XRotor Micro 60A 4in1 BLHeli-32 DShot1200 (Overview, Spec) - HobbyWing hobbywing.com/goods.php?id=653 (2) Hobbywing XRotor Micro 60A 4 en 1 BLHeli-32 DShot1200 3-6S ESC pour drone de course FPV Quadcopter US$61 - AliExpress fr.aliexpress.com/item/… (3) XRotor Micro 60A 4in1 BLHeli-32 DShot1200 (User Manual) - HobbyWing hobbywing.com/products/enpdf/XRotorMico60ADShot1200en.pdf / to continue, ...

/Continued, ... (4) GARTT 4pcs/6pcs ML 3515 400KV Brushless Motor for QAV Quadcopter Multicopter RC Drone ()With Spec)- AliExpress US$118 4PCS fr.aliexpress.com/item/…

Now let us refer to the following picture for discussion.

Question 1: Troubleshooting suggestion. Are you using the CTR pin? You can use Pico ADC pin to measure the current (11.75mV/A).

Ah, locking down lunch time. See you later.

Troubleshooting suggestion 2: I would suggest to calibrate the motor current for the following spec: (i) Power: 22.2V, (ii) Throttleing rate: 50% with (iii) current about 3A.

So we are ready to do the point to point wiring:

Question 2: Can you show me a photo of your wired thing?

Question 3: Can you show me the listing of your Pico Thonny MicroPython code, with the following functions:

(a) 4 GPIO pins with 50% PWM Throttling rate,

(b) Pico ADC pin measuring the total motor current (11.75mV/A)?