Re: ARM7 and quadrature encoders

Started by Joel Winarske December 5, 2007
> I've often wondered if I could come up with a design in a cpld
> or small fpga if there'd be a market for a selling that or the
> IP (Intellectual Property) as a quadrature chip.
>

There's not much involved:
http://www.fpga4fun.com/QuadratureDecoder.html

An Engineer's Guide to the LPC2100 Series

Joel Winarske remarked: Tuesday, December 04, 2007 4:35 PM
> There's not much involved:
> http://www.fpga4fun.com/QuadratureDecoder.html

Right, in the quadrature decoding itself, but in the counter,
and the interface circuitry, there can be some complexities and
value added.

Randy
www.newmicros.com
--- In l..., "Randy M. Dumse" wrote:
>
> Joel Winarske remarked: Tuesday, December 04, 2007 4:35 PM
> > There's not much involved:
> > http://www.fpga4fun.com/QuadratureDecoder.html
>
> Right, in the quadrature decoding itself, but in the counter,
> and the interface circuitry, there can be some complexities and
> value added.
>
> Randy
> www.newmicros.com
>

There could be! One example might be a single pin to load the current
count into the output registers (shift register?) so that, at the
moment of the sample, the count is stable. It's obsolete when read,
but stable.

Or maybe the count is frozen when CSn goes active but most SPI gadgets
want to frame the data in 8 or 16 bit quantities surrounded by CSn's.

A separate pin would be better.

Might as well include an I2C interface and, if pins aren't an issue,
consider a parallel IO interface using some minimum number of pins.
Maybe 8 bits at a time plus a few control signals.

The problem with FPGAs is that you pretty much have to sell them board
and all. There isn't much available in a DIP or SSOP package. QFPs
and BGAs are probably out of the question.

The OOPic world could really use something like this!

One low speed variation on the theme: http://www.awce.com/pak7.htm but
it has WARTS in terms of the way it measures distance.

Richard