OK, so adjusting the pulse time outside the classic RC values certainly seems an easy way to do it.
If you were stuck using RC equipment though and willing to modify a servo slightly, if the servo has the position pot 1:1 with the output shaft then you may be able to increase the rotational range by adding some resistance in series with each end of the pot. This would make the rotational range of the pot a smaller percentage of the voltage divider so in theory it could increaase the amount of rotation over the same RC pulse range. This ignores the fact that you have increased the impedance of the voltage divider so there may be a side effect depending on what is reading the voltage. Anyway, I have never tried this, it is just a partially thunk out idea, but if someone were in a pinch and wanted to try something this might do the trick.
Well…
If you won’t take my word for it, then I can spend an hour uploading a crappy video of it, on my 56k can.
I really am getting almost 180 degrees out of the box.
Perhaps you’re using older 5645’s, Jim?
Maybe they changed it in the new ones?
Is that mean I can’t perform a 180 degrees rotation even with the help of the servo programmer? Damm, I’m stuck with the gear stuffs and that means I have no choice but to wait for weeks for the servo mount gear from servocity…
First off, if getting full functionality out of the servo requires buying a separate programmer, that sucks… c’mon HiTec! If that’s the case, it’s really time someone reverse engineer the programmer protocol and post some schematics and code for those who don’t want to shell out the cash for the HiTec programmer.
EddieB: I don’t think that’s gonna fly. Adding any uneven resistance to the pot instead of increasing the available range of motion, it will decrease it as the pot will no longer scan from 0 to 100%, instead it would range from +AddedResistancePercentage to 100% or 0 to 100-AddedResistancePercentage. Adding even resistance to both sides will result in the pot’s full motion reading a smaller range (smaller with increase in the extra resistance) to be registered around the center reading.
All the servos I’ve cracked open really do swing from near zero resistance to many MOhms at 180 degrees. While you may physically be able to turn some of these pots past 180 degrees, the measurable positions outside of the Many (and exponentially increasing) MOhm positions will be very limited.
well I have not taken apart very many servos and the ones I have I was not really looking at the existing circuitry a whole lot. 
I actually should have been more clear by saying add the same resistance to each end of the pot. My thunking was based on your averge off the shelf potentiometer having a 270 degree range and figuring your typical servo only used 90 degrees of that. If the center of movement was half way through the pot then it would stand to reason the travel was from 1/3 to 2/3 of the pots range, so the voltage divider it formed would be from 1/3 to 2/3 of the range. Even if they are only 180 degree pots in the servos then you would instead go from 1/4 to 3/4 of the range over 90 degrees of motion, again “assuming” the servos are center referenced. By adding the same resistance to each end of the pot you can make the full rotational range of the pot a smaller part of the complete voltage divider. So, if you have 6 volts supply, an unmodified 180 degree (pot in the) servo going 90 degrees might output from 1.5 to 4.5 volts with 3.0v being center. Using 180 degrees for the pot rotational range, say the pot is 10K value and then you add a 5K resistor to each end for a total resistance of 20K. your voltage divider still gives you 3 volts ar the midpoint but now one end of the pot is 6V * (5K/20K) = 1.5V and the other end is 6V * (15K/20K) = 4.5V. The wiper of the pot now has to travel from 0 to 180 degrees to get the same voltage output as it did when only going 90 before adding the resistors.
Am I missing something here about the servo circuitry that reads the voltage divider output of the pot that makes this impractical to implement?
PS: the reason I am pondering through this is the tilt and pan gimbal might be a very interesting way to put a camera on the bottom of a plane and being able to swing from full left to right would be pretty sweet, imo.
I think only that the wiper runs end to end in 180 degrees. I think I had the effect of the added resistance backwards and you were/are correct.
There is some discussion on the micromagic-sys.com forum about the Hitec “HMI” protocol for talking to digital servos.
The info is still pretty sparse though.
The only thing that’s reasonably clear is how to get position info from the servo.
It looks like Hitec is using the same basic PWM scheme as the analog servos, but if you send it a much shorter pulse (50uS, 100 uS, etc.), then it interprets it as a ‘command’. The control signal needs to be ‘open-collector’ with a pullup, so that you can send it a command and read the response back on the same wire.
Pete
I tested a new one right out of the box to make sure before I wrote anything. Perhaps I programmed them for you. I have done it in the past, but I can’t remember if I did it or not, do you? I would not have done it on my own though, I’d have to have been asked… Also, we are way to busy to do this anymore in case anyone was wondering, sorry…
Just to add my comments 
Jim - With digital servos like the HS5645 does 900us and 2100us always move teh servo to the end positions - those end positions (e.g. -45 or -90 degrees) being programmed in?
I guess this would make sense since for the average RC market since a range of 900us-2100us would give greater precision for the servos operating ±45 degress, adn then us roboteers who want ±90 degrees accept a slightly less precision (but since we are genrating the signals from a microcontroller rather than an RC handset we get exactly what we want)
Jim - do you still have the Servo Programmers in stock?
can someone post a like to where they saw how to get the position out of the HS5645 servo?
Thanks
The servo programmers are on the servo page.
Hi Guys,
I just got the hitec digital servo programmer, but i don’t have any charger that suits this programmer. The programmer uses an internal 1100mA, 4.8v nicad battery.
Just some question here…
Is it possible to charge the programmer using a DC Power supply, output at 4.8V and 1.5amp?
Thanks for your help! Appreciate
Please see this tutorial. It covers why the thing doesn’t have a charger.
lynxmotion.com/images/html/build100.htm
Although you can use a power supply to charge a lead acid battery it’s not recommended for NiCad batteries. The battery can be charged with any hobby battery charger, (the ones for RC car and plane use).
lynxmotion.com/Product.aspx? … egoryID=48