The flight controller needs to be sent 4 PWM signals at greater than or equal to 5 volts. Since the Beaglebone Black(BBB) GPIOs can supply only 3.3V I needed to change the signal from a 3.3 volt one to a 5 volt one. In order to do this I looked up online and mostly everywhere I have found this circuit for logic converter from 3.3V to 5V.
But when I connected the low side to my Beaglebone GPIO's and the other side to the flight controller and then switch on the BBB it doesn't boot up. I have already fried one BBB. When i measure the low side without connecting to the BBB I find that the voltage is around 2 volts. I think this is the problem because in multiple places in the BBB System Reference Manual it is given that no voltage should be applied to any of the input pins before the BBB properly boots up. Could this be the problem?
If so then how can i go about rectifying it? For the time being I am using optocouplers to isolate the BBB from the high side.
So, to sum it all I want to know :
- How do you make sure that no voltage comes back into the BBB when its an output pin?
- And since no voltage can be applied to the BBB before the system boots how can i disable devices that are connected to the BBB and going to send in data to the BBB not send any signals till the BBB boots up?
This will be really helpful for my project as I cannot manually disconnect/connect wires every single time the BBB is starting up.