#!/bin/bash
#                                                                         
# Simple Servo controller using the PWM ports on an Infocast 3.5" (Chumby)
# The serial in/out pins can be reconfigured as PWM ports                   
# Servos are pulsed at regular intervals, up to 50 times per second (20msec)
# The length of the pulse determines the position and can be from         
# 1msec to 2msec where 1msec is the home positon and 2msec is farthers out
# Some servos vary slightly from these numbers                                 
# The Chumby processors signal at 3.3v which may not work for all(most?) servos
#                                                            
                                                             
# moves a servo to whatever value is stored in the variable i  
move_servo()                                                   
{                                                              
 # Set an "active" and an "inactive" period of 3750 cycles each
 # 1msec = 375 (0x177) cycles 2msec=750 (0x2ee) cycles              
 regutil -w HW_PWM_ACTIVE0=0x0$(printf "%x" $i)0000                 
                                                                    
 # Set the crystal to divide by 64, and have a period of 7500 cycles
 # frequency should be about 50hz (500hz was 750) or 20msec period       
 regutil -w HW_PWM_PERIOD0=0x005b1d4c                                    
                                                                         
 # Turn on PWM0 Do we really need this every cycle or only the first one?
 regutil -w HW_PWM_CTRL_SET=0x00000001                                         
                                                                               
}                                                                              
                                                                               
# Set bank 1, pins 26 and 27 to be PWM output                                  
regutil -w HW_PINCTRL_MUXSEL3_CLR=0x00f00000                             
                                                                         
# swing full range and back                                              
# the regutil calls are slow enough with small increments that no sleep is neede
for i in {375..750..8}                                                          
do                                                                              
  move_servo                                                                     
done                                                                            
for i in {750..375..-8}                                                         
do                                                                              
  move_servo                                                                     
done                                                                            
                                                                                
exit 0