[General] Possibly complex question as I don't yet have a full understanding of these devices.

Possibly complex question from someone who still does not have a full understanding of AVR/Pic pin name definitions.

I have managed to figure out that PIC's etc have ports A,B,C etc and that those port have direction registers etc and related pins but...

I am looking at making a charlie plexed display controller that displays hexadecimal values on an LED display to whit i am looking for the smallest PIC or Arduino device in each class that is available in DIP packaging that can do the job by number of digits, there are some specifications to what I am looking for because I am working with parallel input not serial and no other IC's must be involved.

As an example.
For two Hexidecimal digits would require.
8 Inputs for values. A nibble each in Hex.
8 Outputs would be required for 7 segment LED's including the decimal point which will be used.
2 returns ( inputs ) would be required for 2 charlie plexed lines from the CC on the displays via transistors.
Making a total of 10 inputs and 8 outputs if I am correct with my understanding of how this works.
It would also of course need enough RAM/ROM to deal with the program making the above happen.

Now with the above in mind I am trying to figure the smallest single PIC/AVR/<insert name of micro here> that will allow for
2 Digits ( 10 inputs , 8 outputs ) as above
4 Digits ( 20 inputs , 8 outputs )
8 Digits.( 40 inputs , 8 outputs )

Can someone with a good understanding of these micros help me out so I don't end up purchasing a micro to small or to large and so that I can
determine how many micros I will need, I.E if there is no micro with 40 inputs and 8 outputs I will need 2 micros at 20 input 8 output.

Cheers in advance all.

Hi,

2 returns ( inputs ) would be required for 2 charlie

Click to expand...

You say "input" because you think of current flow.

But indeed it is an "output".
Think about "information" flow. The microcontroller sends information to the display: which digit is "ON".

Input: there is never a significant current flow of interest. (When pullup is enabled, there maybe current flow, but just to prevent the signal from floating and reduce external part count).
Output: the microcontroller forces HIGH or LOW to enable current flow. Often to drive a load.

But the drive current capability is limited.
Read the datasheet about
* output drive capability per pin (not the "absolute maximum rating")
* power supply pin current capability

And like always: draw a sketch for us ... and for you. It doesn't need to be perfect, paper and pencil is OK.
Schematics are far easier to read than a lot of text. And it helps to avoid misunderstandings.

Klaus

KlausST said:

Hi,


You say "input" because you think of current flow.

But indeed it is an "output".
Think about "information" flow. The microcontroller sends information to the display: which digit is "ON".

Input: there is never a significant current flow of interest. (When pullup is enabled, there maybe current flow, but just to prevent the signal from floating and reduce external part count).
Output: the microcontroller forces HIGH or LOW to enable current flow. Often to drive a load.

But the drive current capability is limited.
Read the datasheet about
* output drive capability per pin (not the "absolute maximum rating")
* power supply pin current capability

And like always: draw a sketch for us ... and for you. It doesn't need to be perfect, paper and pencil is OK.
Schematics are far easier to read than a lot of text. And it helps to avoid misunderstandings.

Klaus

Click to expand...

Hi Klaus, I can provide a schematic for all of what I am talking about barring the micro but as I don't know which micro has the correct number of pins for what I am wanting to do I would just have to fake one until I know what to use is that still appropriate?

Hi,

as already said:

It doesn't need to be perfect, paper and pencil is OK.

Click to expand...

Klaus