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got the servos, got them working



The servos were delivered today, and I started working on them once I came back home from work. 

The initial set up I had with RPi.GPIO was... a failure. 

When connected, the servo would just twitch and continue to groan with uncertainty about where it should position itself. 

Wanting to see what it should actually do, I fired up my Arduino that's been inactive for quite some time, connected the servo and loaded up the Servo library. It worked like a charm. The difference between a real-time PWM and a soft PWM was very visible. 

For a while, I was thinking about maybe using the Arduino as the servo controller and have the Raspberry Pi just send a single high signal that would trigger the Arduino to move the servo. However, the extra size and power that would be required put me back to my senses.

I have to say I was pretty discouraged. It was probably because I was really expecting whatever I had implemented to work right off the bat. After eating a late dinner, I pushed myself to try more. 

I tried installing the WiringPi library, but after reading about it, it didn't seem much different from RPi.GPIO, so I didn't bother to use it. 

I then thought I should maybe install the Occidentalis OS that is developed by Adafruit, seeing how it comes with servo kernels. Felt like starting from scratch (at least in the Raspberry Pi side) should be a last resort option, so I decided to try to find something else. 

Finally, I landed on ServoBlaster. It relied on writing a duty cycle value to a location in the system, but it worked smoothly, and beautifully. It also did not need to constantly drive the servo a constant signal but activated only when the position was changed (with a timeout value in the initialization parameters). 

echo 5=70 > /dev/servoblaster 

The "70" is the amount of time the signal will be high. The cycles are counted by 10 us (microsecond), making the "70" 700 us, or .7 ms. This would put the servo near the 0 degree position. 

echo 5=230 > /dev/servoblaster

This would put the servo near the 180 degree position.

Had to use system calls through the os module, but once implemented, it finally works.
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