RC Servo Controller with preset

Below you find the schematics of the servo-controller I use. It is based on the PIC 16F84A from Microchip. To obtain a good resolution, I use a version of 20 MHz. It's interfacing to the serial port with a rate of 38400 baud. The PIC is controlling 12 servos in parallel with a resolution of 240 steps over 90 degrees rotation.

Look at the code for more details.

Each servo is controlled by first sending a command byte (0xf0 + iS) and then a data byte D, representing the desired servo-output. iS is the index of the target servo 0,1,..,11; D = 1,2,..,239. The controller maintains each servo-output until changed by command.

When writing command 0xff followed by a databyte equal to 0x00, the current servo-values are stored as preset values into the eeprom of the PIC. At startup the PIC will initialize the servo-values with these preset values. This mechanism provides a convenient way to maintain presetvalues up to date.