Can I use analog pins as digital IO pins

Hello all,

can I use analog pins as digital IO ?.

if yes then can I implement Charlie plexing method ? while I am using this analog pins as digital output ?.

Yes analog pins can act as digital pins as well (on standard common arduino such as UNO or MEGA)

“Charlie plexing” requires to use the tri-state logic properties of microcontroller pins:

1/ OUTPUT + HIGH (5 V)
2/ OUTPUT + LOW (0 V)
3/ INPUT (pin is in a high-impedance state so basically “disconnects” that pin from the circuit - little or no current will flow through it).

By playing with those 3 states and properly setting up your array of LEDs you can drive many LEDs from a limited number of pins.

wikipedia can probably give you more info on how to set this up

SureshKumar2610:
Hello all,

can I use analog pins as digital IO ?.

if yes then can I implement Charlie plexing method ? while I am using this analog pins as digital output ?.

This is strictly speaking something to look up in the specification of the particular Arduino board you
are using. The Uno and Mega and other boards using AVR ATmega micro-controllers all support digital I/O
on every pin, but other more exotic variants may differ - as always the datasheets and product webpages
are there to tell you such important details.

So yes you can Charlieplex on AVR boards - be careful to check the maximum current constraints
(again this varies according to the particular Arduino variant).

Be warned that the A6 and A7 pins found on some boards based on the surface-mount version of the ATmega328P can NOT be used for digital I/O. When they made the 32-pin surface-mount chips (the other packages are 28-pin) they connected two of the new pins to the analog input multiplexer. Those two pins are not connected to any of the digital I/O registers so that can only be used for analog input.

Very useful information.

Thank you very much. I need above 30 digital io pins which arduino suitable ?. except mega

You can consider shift registers as one option

You can also explore chips called “port expanders” (MCP23S17 or MCP23017 = 16 more input and you can connect easily 2 (or more) so you get your 32 pins) that connects through the I2C or SPI to your arduino.

of course you need to consider timing constraints based on what you want to achieve with your pins.

then any arduino will do.