Hitec HMI

Is it possible to use the micro servo controller to control Hitec servos with HMI protocol? Specifically I would like to be able to generate a 50mSec pulse via a Pololu servo controller and then have it’s output go tristate so I could receive the return pulse from the servo via a paralel microcontroller input.

You can certainly use any Hitec servo with any of the Pololu servo controllers for normal position control, but all the micro servo controller does is output position pulse-width signals (0.25ms-2.75ms). If you’re going to have a microcontroller hooked up to the servo signal pin already you might use that to generate the special pulses for the HMI interface.

I took a quick look around, and certain Hitec and Kondo brand digital servos have this similar feedback feature, and both brands also make (pricy!) servocontrollers that make use of this feature. I haven’t worked with either of the controllers, but the protocols are similar enough that either might work with the other’s servos (I would look into this further before buying anything). Anyway, these controllers also specifically interface with proprietary PC software, so they wouldn’t solve your problem either.

Looking at the Hitec HMI Protocol, it should be just as simple for you to generate the pulse from the microcontroller you were planning on using to read the return signal, but the pulse width to get a position return signal should be 50us (0.05ms), not 50ms. Probably just a typo.

What’s your project?

-Adam