Its been a while that i am working on an autonomous vehicle and some major parts are tested and still going on with the project. For this project its better to have a manual override control via RC remote controller.
After researching the RC controller and receiver i have found out the RC remote controllers use PPM signals to control the servo and ESC. In one of my earlier post's i have mentioned reading the receiver outputs and tested how it can be controlled.
PPM signal out from the RC receiver.
I have on of my bixler controllers and finally able to use it for this project. Hobbyking 6 channel receiver and 4 channel transmitter is used for this and i wont guaranty that this will or will not work with your projects. The PPM signal will vary depending on different vendors. I read all the output of the receiver and log it for further reference.
Since the code will be very very simple i decided to use ATtiny13A-PU as the micro controller. Lets think of a way to switching and got an idea from one of my very old project built when i was in school. Bilateral switching so used CD4066 which is like a switch. Since this is CMOS IC i have fried lots of it on old days. (Handle with care, static will kill the chip / high voltage also will do the same). Combining these two i was testing this circuit on an bread board for weeks. (circuit design done by me). If anyone want the circuit here it is down below.
After loading the sketch the ATtiny in placed on the board
I design the circuit to control one servo and ESC for motor. If i need more still can go for more I/O by upgrading the circuit.
This is a test video. In normal mode servo/ESC is controlled by another micro-controller and once the remote controller is switched on the override circuit detect the Transmitter presence and switch to Remote controller mode and tadaaa... now can control the servo/ESC from remote and once the remote is switched off it will automatically handover the servo/ESC controls to micro-controller
By reading PPM signals you can control anything depending on the transmitter and receiver channels and micro-controller capacity. The theory, circuit and concepts works for me . I wont assure that it will work for everyone.