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Sienna
02-11-2009, 05:08 AM
Has anyone implemented a biped using the HMI serial protocol? Information on it on the web seems sparse. And the only controller right now that I could find that supports it is $250.

I was looking to possibly roll my own controller, and am hoping someone has a library or something to implement the HMI serial protocol.

If no one does, I might have to seriously look into selling all the HSR5990TGs / SES I have, and re-invest in the Bioloid servos and brackets.

DresnerRobotics
02-11-2009, 07:45 AM
I hate to be a downer, but from what I've heard its probably not even worth delving into. I've read multiple threads on people trying to use it, and all have ended in disaster. I've got some 5990s myself, and I haven't even bothered.

Even without HMI, they're going to be decently stronger than the bioloid servos though, which cap at about 280oz-in holding torque. Major advantage to going with the bioloid of course, is that creating walking gaits is 10x easier using the 'pose and capture' technique.

Don't get me wrong, I love the bioloid stuff, I just dont know if I'd switch to it if I had already invested in a dozen 5990s + SES, simply due to money lost from selling it 'used'. On the plus side you could afford an entire comprehensive kit with a couple hundred to spare. Tough call...

iBot
02-11-2009, 08:29 AM
The HMI serial mode does work, but it has a couple of limitations. The first is that the speed is only 19200. With 11 bits per byte and 7 bytes per tranacation we have 4 millisec to update each servo. So 20 on a single bus is rather slow. I previously used an FPGA configured as 20 uarts and a picoblaze processor to do them in parallel.

Some times the servos do not respond when read, and I have had some occasional write errors too. Most of my work was on HSR8498 which are earlier version of HMI to the 5990. The Hitec software and cable allows you to check out the HMI serial mode, the software is free and includes the schematic of the cable ( one resistor !).

Following may be of use:

http://robosavvy.com/Builders/i-Bot/HSR8498HB%20Servo.pdf

http://robosavvy.com/Builders/i-Bot/HSR8498_serial.pdf

Let me know if any of the links are out of date.