Filtering noise from a wire

[Demon]

what is the shortest switch activation period that you would expect to need to detect and how quickly do you need to respond ?
generally any key press under 50mS i would just ignore . for basically "static" switches 200 0r 300 mS would be more than adequate

why care about noise and debouncing if quick responses are not required

The only issue I can think of is that I have rotary encoders. Nothing is preventing the user from turning 2 encoders at the same time while on auto-pilot.

There's also the possibility of someone flying with a co-pilot/navigator; that could mean the "possibility" of up to 4 encoders moving at the same time. I want to be ready for that.


My goal is to undercut the market by a wide margin. It's very possible someone with vested interests would try their best to find "bugs" with my product, and drag my name on flight sim groups.

For example: back in college during the late 70ies, Burroughs brought in a main-frame but we thought it sucked. So most a lot of computer students flooded the queues with duplicates of their jobs. The techs from Burroughs were not prepared; the machine failed, badly, and IBM came back. We didn't have vested interests, we were just goofballs, but we did crash the system.

Just look at this thing; couple of switches and 3 LEDs for $140CAD. That's insane. That's worth something like $20 at most. There's very few competition, so they pretty much do as they please.

I'm not the next Delorean, but I still expect resistant.

[richard]

I have rotary encoders. Nothing is preventing the user from turning 2 encoders at the same time while on auto-pilot.

rotary encoders are a completely different story to switches, you have virtually no chance of reading multiple re's via i/o extenders with any confidence that steps and direction changes won't be missed

[Ioannis]

Regarding the Rotary encoders Richard covered it 100%.

With shielded wires I am pretty sure you won't have any problems. Forget about R's and C's, just read two times the switch state and your are done with debounce.

As for long or short wires acting like antennas, well, the general statement "long wires act like antenna" is not quite right. It depends on the frequency we are talking about. For example, 10cm may seem very short, but this is an antenna for 750MHz and the 10m is an antenna for 7.5Mhz. So, which one may be a problem for you? It depends on what signal sources you have nearby, right?

Best way to deal with all frequencies is both cable shielding and metal case box wherever there is a possibility of interference.

But I think we are getting crazy on this...

Ioannis

[tumbleweed]

rotary encoders are a completely different story to switches, you have virtually no chance of reading multiple re's via i/o extenders with any confidence that steps and direction changes won't be missed

+1

If you're trying to use an IO expander to do that good luck!

[Demon]

Challenge accepted 😁

[Ioannis]

Even if you have the fastest MCU to decode rotary encoder, the bottleneck is the I/O expander and will not be fast enough to follow users speedy fingers!

Ioannis

[Demon]

Even if you have the fastest MCU to decode rotary encoder, the bottleneck is the I/O expander and will not be fast enough to follow users speedy fingers!

Ioannis

This is a signal from an EC11 rotary encoder.

5vdc with 10:1 probe
.1 volt / division
.2 ms / division




It takes about 2.5 time divisions to activate; so about 0.5ms.

MCP23017 I/O Expanders can run up to 1.7 MHz in I2C mode.
MCP23018 I/O Expanders can run up to 3.4 MHz in I2C mode.
MCP23S17 I/O Expanders can run up to 10 MHz in SPI mode.

I'm not keen on the new addressing mode on the MCP23018 version. I'm hoping the MCP23017 is fast enough at 1.7 MHz in I2C mode. At worse, I'll learn how to use the MCP23017 at 10 MHz in SPI mode.

(nope, haven't done any math to check if it's possible, mainly cause I have no clue how to do that properly )

[tumbleweed]

MCP23017 I/O Expanders can run up to 1.7 MHz in I2C mode.
MCP23S17 I/O Expanders can run up to 10 MHz in SPI mode.

That's the wire speed... you'll never get the code to run anywhere near that fast except for a single byte transaction.
You won't get I2C to run that fast without active pullups, and getting the PIC to do 10MHz SPI depends on your system clock.