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[DPRG] PIC does motors

Subject: [DPRG] PIC does motors
From: Earl Bollinger earlwbollinger at comcast.net
Date: Tue Jan 6 22:03:01 CST 2004

In my opinion, I think they need to work on it some more.
I took a look see, but it is a future product, it's not out yet.
The data sheet says it has three PWM channels but this seems to be in
conflict throught their doc's, and two channel quadrature encoder, et
cetera. But it only has 768 bytes or RAM, 4k or 8k of Flash.
Note I only see one quadrature encoder built in, for robots we really
need at least two.

It does 14 bit PWM, which is worded to look like 14 channels on first
glance. But one place says two PWM channels with 4 complementary
outputs, another chart says up to 8 PWM channels, and another says 2. of
course maybe that's the weird 28 pin versus 40 pin package info.

It does have 4 timers though. But I don't know why they'd name them
Time0, Timer1, Timer2, and Timer5. What happened to 3 and 4?

The 40mhz clock gives you up to 10mips. Other competing MCU's especially
RISC are getting 10mips at 10mhz or less clock speeds.
I didn't see a graph on power consumption at different clock speeds
though.
So I assume the low power features only work best at low clock speeds
and I powerdown mode.

Why only one quadrature encoder? What are the CNC guys supposed to do?
Using one MCU per motor complicates motion control a lot in a lot of
things.

So I guess we need to wait to see what the real chip really has when
they release it. Right it looks like you'd need two of them to do quad
encoding.

I think the Motorola DSP56F805 and 56F807 still does better a job than
that. 80 mhz, 16 bit processors, 12 bit ADC's, up to 16 timers, it has 2
quad encoders, 6 PWM channels, etc. there to play with. Now that's more
sutable for motion control to me.



-----Original Message-----
>From: dprglist-admin at dprg.org [mailto:dprglist-admin at dprg.org] On Behalf
Of Roger Arrick
Sent: Monday, January 05, 2004 11:39 AM
To: dprglist at dprg.org
Subject: [DPRG] PIC does motors

Anyone seen the new 40-pin PIC micro with built-in
PWM channels (14 of them), 200Khz A/D, and encoder
interfaces?

http://www.microchip.com

Click on PIC microcontrollers, then select Motor control

PIC18F4431



Roger Arrick   -  mailto:roger at robotics.com
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Arrick Robotics  -  http://www.robotics.com
Step Motor Systems, Positioning Tables, Mobile Robots, Tech Info
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