This falls right into my current robotics project. I will be using my
68HC11 as the master controller for a couple of PICs. Slight dillemma to
still deal with is the inter-processor communications (IPC). If I stay
with two processors, then serial (RS232) will suffice, but more
processors, then I need some form of network. This will be new to me.


> -----Original Message-----
> From: Thomas McGahee [SMTP:tom_mcgahee@SIGMAIS.COM]
> Sent: Thursday, January 20, 2000 2:10 PM
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      Re: General walker stupidity: Divide and Conquer!
>
> Adam has brought up a good point. Distributed processing is
> a very useful technique. Each sensor/microprocessor combination
> has its own private interrupt mechanism, and a means to
> respond quickly to the local stimulus. Such local action might
> include some form of immediate action such as movement towards
> or away from an object, and two-way *communication* with
> a Master CPU that controls the "big picture".
>
> Other examples of specialized processing would be:
>
>      An LCD controller that communicates serially;
>
>      A "math co-processor" PIC that does all the math
>        stuff, and which you communicate with over
>        a serial line;
>
>      A Data Ram that accepts an index number and then
>        returns a sequence of data such as ASCII text
>        string messages for the LCD, or Conversion Table Data;
>
>      A Stepper Motor Controller that moves a stepper motor
>        to an "absolute position". You tell it "X=12,345",
>        and it moves from the current location to the one
>        specified;
>
>      A Servo Controller that accepts an ID and a Position value and
>        then moves one (of several) servos to that position.
>
>
> All of the above PIC based "distributed processing" functions already
> exist. Many of them have been designed by members of this list.
> Sometimes
> two or three low-end PICs can do a job better than one expensive cpu.
>
> It is also often MUCH easier to program a Master CPU to control a
> couple of "local intelligence" PICs than it is to try and program
> a single PIC with limited interrupts to do all the tasks. As the
> ancient Romans used to say, "divide and conquer".
>
> Fr. Tom McGahee
>
>
> -----Original Message-----
> From: Adam Bryant <adamdb@JUNO.COM>
> To: PICLIST@MITVMA.MIT.EDU <PICLIST@MITVMA.MIT.EDU>
> Date: Thursday, January 20, 2000 1:22 PM
> Subject: Re: General walker stupidity
>
>
> >I would argue for a distributed approach using many lower cost
> processors
> >rather than 1 expensive processor.  For the price of one HC11
> whatever
> >processor you could purchase a 16F84 and a number of 12C508/9 OTP's.
> The
> >8 pin PIC's (including some of the newer ones that have onboard A/D)
> are
> >perfect for motor/servo controllers, sensor controllers,
> communication
> >controllers, etc.  By distributing the processing required for motor
> >control and whatnot to the small/cheap PIC's, the master controller
> >(16F84) can concentrate solely on the higher level functions of
> whatever
> >behavior you want your robot to have.
> >
> >We (myself included) tend to think too much in terms of one
> >microprocessor doing absolutely everything which usually ends up with
> >extremely complex code.  Whereas with the distributed approach, each
> >component (motor, servo, sensor) has a limited job to do that can be
> >coded much more simply.
> >
> >Typical hobby walker robots use 2 or 3 servos, 2 touch sensors, and
> >possibly an IR ranging detector.  Use one 12C508 to control the
> servos, 1
> >508 to monitor the touch sensors, and 1 508 to handle the IR ranging.
> >Use a 16F84 as the master and tie them all together with I2C and you
> >would have a very powerful, flexible walker.
> >
> >Just my $.02 worth,
> >Adam
> >