100hz pulse rate with 8 chan servo controller

Hello, I’m building a quadrotor helicopter and I really like the features of your servo controller. I’d like to reduce the number of channels from 8 to 4 and increase the pulse rate from 50hz as you specified to 100hz. This will give me better control and stability. I think this could be done by using four OR gates if the channels are pulsed one by one, correct? For example, channel 1 and 5 will be connected to one OR gate, and I would have to command both channel 1 and 5 to the exact same location, the single output from the OR gate would now would output identical high pulses but occurring twice as often, correct? I should also be able to accomplish the same using diodes with the anodes connected to the servo controller and the cathodes connected to a pull-down resistor and the servo, correct?

For this to work, I’ll need to know in which order the channels are pulsed. Is it simply from 1 to 8? or is it different? Looking at the schematics, it looks like all the firmware does is bit shift when the timer reaches whatever value the user sets, so I’ll assume it’s 1 to 8 (or 8 to 1, wouldn’t make a difference really).


The servo controller outputs are overlapping (the firmware is based on the 16-channel versions, where simultaneous pulse generation is absolutely necessary). The pulses are generated in groups of 4, so your ORing idea could still work, but I really don’t recommend it since you could get weird glitches if one of the two pulses gets updated before the other.

Because the pulses are already getting generated in overlapping sets, it’s possible for us to modify the servo controller to generate 100 Hz output directly (on all 8 channels). I’m not sure what your budget is for the project, but if you’re interested, I can get you a quote for customizing the servo controller. (Customizations typically cost at least a few hundred dollars.) Alternatively, if you have a high-visibility project, we might be able to help you out in some sponsorship sense. If you’re interested in any of these possibilities, please contact us more directly (i.e. call or email us).

- Jan