RE: [SeattleRobotics] little networks - [Re: The Wozniak Test
Can your MSCC20 multi-servo controller chip do "group" or coordinated moves?
That's something that seems to come up often with walking 'bots. I've been
reading through your servo commands (quite a few!), but didn't spot it.
> -----Original Message-----
> Hmmm, my servo controller chip is a 16F877, and can run up to 20 servos
> with velocity control [and even acceleration control on some versions],
> and with minimal use of code space. I used the compare modules and
> interrupts, and overall duty cycle is circa 5-10%.
> This left me so much code space and duty cycle available that I
> implemented my complete walking machine CPG gait generator on the same
> chip, along with FSM logic that could read sensor input, and branch
> between different gaits [up to 126 gaits stored in eeprom], for automatic
> turning, backing up, etc.
> I used it on my hexapod Nico-6, along with a BS2 for general
> programmibility. I coded the BS2 with a bunch of routines to read sonars,
> command the CPG chip via RS232, and to run the Robothon walker contest.
> The BS2 was just barely able to handle the job, but the 16F877 had no
- oric_dan said: Wednesday, December 02, 2009 12:12 PM
> The netbook becomes the high-level brains, plus usefulHi Dan,
> for wifi comms, of course.
I really don't think USB to micros is the way to go. I think CAN
is a much better approach. A webpage, or spreadsheet, of
features would probably be a good thing done. I'm not sure I can
do it. But here's a first blush. I would like a network that was
muyltidrop, peer-to-peer, availble on small micros.
CAN Ser SPI I2C USB Ethernet
Small Sys x x x x
Multidrop x x x x
PeertoPeer x x
CSMA/CA/CD x x
Noise Immun x x
Video x x
So CAN is favorable for everything important except video (also
not all small micros have it, but SPI peripherals can
compensate). Ethernet is suitable for everything except
reasonaly small micros we'd really like to use. USB misses on
almost all desireable traits except video (but that solves
webcam issues). It requires a host (master-slave) arrangement.
It is not suitable for small systems (particularly the hosting),
and it takes hardware and software at every micro to talk. It is
not multidrop, so every node has to have a hardware channel to
host or hub.
(My experience with this was seeing it in action on the Smart
Car CAN Bus, where many controller units offered up their
reports on the bus, and anything in the car that needed that
information could just grab it when it came by. For instance,
both the throttle and the transmission could watch where the
operator put the gear selection and the pedal. The front panel
could read the engine water temperature and know if it should
set a warning. Nobody asked for data. It was always there,
updated at the necessary rate, depending on expected latency
So I'd think your best solution is from your netbook use one USB
for Webcam, and one USB as a bridge to CAN or something like