Equivalent circuit of an Arduino ATM328 digital input pin?...

[server]

My first Arduino project (using an ATMega 328) is triggered by a roughly 5V to 0V edge and works fine overall. (It sends a series of servo arm movements.) But I\'m still playing with various simple front end circuits to deliver that edge.

I\'d like to simulatie these. What would be the simplest way to represent a digital input pin of the 328 please? And with the built in PULL-UP option?

Terry

 

[Phil Hobbs]

On 2020-08-03 07:09, terrypingm@gmail.com wrote:

My first Arduino project (using an ATMega 328) is triggered by a
roughly 5V to 0V edge and works fine overall. (It sends a series of
servo arm movements.) But I\'m still playing with various simple front
end circuits to deliver that edge.

I\'d like to simulatie these. What would be the simplest way to
represent a digital input pin of the 328 please? And with the built
in PULL-UP option?

Terry

For SPICE purposes, a CMOS input is an open circuit with a couple of pF
capacitance to ground. The pullup is specified as a resistance of 20k
to 50k (see Section 28 of the datasheet, so use that.

<http://ww1.microchip.com/downloads/en/DeviceDoc/Atmel-7810-Automotive-Microcontrollers-ATmega328P_Datasheet.pdf>

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Jasen Betts]

On 2020-08-03, terrypingm@gmail.com <terrypingm@gmail.com> wrote:

My first Arduino project (using an ATMega 328) is triggered by a roughly 5V to 0V edge and works fine overall. (It sends a series of servo arm movements.) But I\'m still playing with various simple front end circuits to deliver that edge.

I\'d like to simulatie these. What would be the simplest way to represent a digital input pin of the 328 please? And with the built in PULL-UP option?

use the circuit in the data sheet.

--
Jasen.

 

[Terry Pinnell]

Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-08-03 07:09, terrypingm@gmail.com wrote:
My first Arduino project (using an ATMega 328) is triggered by a
roughly 5V to 0V edge and works fine overall. (It sends a series of
servo arm movements.) But I\'m still playing with various simple front
end circuits to deliver that edge.

I\'d like to simulatie these. What would be the simplest way to
represent a digital input pin of the 328 please? And with the built
in PULL-UP option?

Terry


For SPICE purposes, a CMOS input is an open circuit with a couple of pF
capacitance to ground. The pullup is specified as a resistance of 20k
to 50k (see Section 28 of the datasheet, so use that.

http://ww1.microchip.com/downloads/en/DeviceDoc/Atmel-7810-Automotive-Microcontrollers-ATmega328P_Datasheet.pdf

Cheers

Phil Hobbs

Thanks Phil, but although I didn\'t study all of the other pages (294 in
total), nowhere did I see the all important clamping diodes?

After further research I settled on this equivalent for my simple
(hobbyist) purposes:

https://www.dropbox.com/s/96z3d24gijzv6d8/328Sim.jpg?raw=1

At the low frequencies in my stuff, I\'ve ignored the couple of pF. I
expect my breadboards introduce more than that.

Terry

 

[Jasen Betts]

On 2020-08-18, Terry Pinnell <me@somewhere.invalid> wrote:

Thanks Phil, but although I didn\'t study all of the other pages (294 in
total), nowhere did I see the all important clamping diodes?

figure 13.1

After further research I settled on this equivalent for my simple
(hobbyist) purposes:

https://www.dropbox.com/s/96z3d24gijzv6d8/328Sim.jpg?raw=1

At the low frequencies in my stuff, I\'ve ignored the couple of pF. I
expect my breadboards introduce more than that.

sounds good to me.

--
Jasen.