This low cost ($14.95) "motor interface chip" can be bought at: http://robotics.scienceontheweb.net
The chip can decode the signals from the "VEX" receiver to control up to 8 motor's H-bridges and 1 driver. It can also receive commands from another microcontroller chip to control the motors. This interface chip uses 3 output pins to control a motor's H-Bridge. Two pins to control the motor's direction and one pin to control the motor's speed by using P.W.M.
The chip uses the input from the two buttons on channel 5 to control the input from the "VEX" transmitter left joystick so that it can control 6 motors. The chip uses the input from the other 2 buttons on channel 6 to lock in the high or low output on pin 14 of the motor interface chip.
The motor interface chip has the following features. These features may not work since a receiver may pick up a signal from anywhere. We assume no responsible directly or indirectly from using these parts. WARNING! NEVER USE THE REMOTE ON A ROBOT THAT CAN CAUSE DAMAGE IF IT GOES OUT OF CONTROL. If your robot goes out of transmitter range; the motor interface chip may shut down the motors and give control to a microcontroller if your robot is using one. This may also be true if you turn your transmitter off.
The motor interface chip does not use a serial port to
communicate with other microcontrollers. This means you can use a very inexpensive microcontroller chip to be the brains of your robot.
Putting a low on pin 2 will cause all the motors to operate at half the power level when using the transmitter.