We are building a mock-up for experimentation with our school group. I have an Unbuntu 20.04 top side computer with Qgroundcontrol 4.0.5, the companion Raspberry Pi 0.0.26 and a Pixhawk with Ardusub 4.0.3. The frame type is a simplerov 4. I purchase four inexpensive bi-directional ESCs which claimed they did not require calibration and brushless motors . As soon as the power is applied the motors begin to spin slowly. I checked them with a PWM tester and discovered they will spin at 1500us and become neutral between 1478 and 1496us.
The MOT_PWM_TYPE is normal. I have tried changing the parameters SERVOn_TRIM and RCn_TRIM to 1486us, I changed the RCn_DZ to numbers between 20 and 40, and have changed the MOT_SAFE_DISARM from PWM enabled while disarmed to PWM disabled while disarmed. Without any change. When it is armed all of the motors spin normally.
Is there anything else I should or could try?