New project - MSFS C++ USB interface

[Demon]

It would figure that the very next day that I send my order, I find an even better way to debounce pushbutton switches using 74HC14 ICs. I hadn't seen this one before. I had only seen the RC design. Oh well, live and learn.

https://hackaday.com/2015/12/09/embe...uttons-part-i/


About not knowing which brand or specs of components used by JLCPCB; I scan their database for components IN STOCK using search parameters like RESISTOR 1206 10K 250MW then sort their output on descending price.

https://jlcpcb.com/parts/all-electronic-components


I looked for a known brand and picked their component with the lowest tolerance percentage; I used Yageo for this project (mainly cause it's the only one that I recognized).

[Ioannis]

Many MCU now have implemented schmitt trigger on their inputs. Maybe this helps ditch the extra chip?

Also software debounce costs nothing but little time to program, right?

Ioannis

[Demon]

Thing is, my buttons leads to I/O expenders, and then all the I/O expanders to the MCU. They first IOE I looked at didn't have schmitt triggers on all inputs.

And honestly, I really preferred to limit extra processing on the MCU and concentrate on USB, and servicing the IOEs. I didn't feel like adding logic for debouncing if at all possible.

The 74HC14 may cost a few pennies, but it should help clean up the signals to the IOEs.

[Ioannis]

Well, I understand the case. With the I/O expanders things are different.

A very good debouncer is desribed in the second part of the article you post. Really neat and ultra fast technique with very low MCU load.

https://hackaday.com/2015/12/10/embe...ttons-part-ii/

But amazing things can a capacitor do! In most cases, with relatively good switch, a series resistor from the switch to the input and a small increase in the capacitor, that is in parallel with the input to the ground, is enough. Used that many times and with rotary encoders too with great results.

The secret is to use that resistor R1 in the following design, to "isolate" a bit the switch from the capacitor.



Ioannis

[Demon]

That software technique of using the last status of the pin (01111111) looks nice on paper, except I'm going to have nearly 100 "controls" (pushbuttons, rotary switches, rotary encoders and rotary potentiometers) on this basic project. And future versions of this project is going to have a truckload more. That's why I'm trying to stay on hardware solutions if at all possible.

I put in 3 orders to JLCPCB so far. Really looking forward to see the end result in person.