I have the following problem, i use a Atmega328 with Arduino Bootloader, and my pin-list is this:
0 - Serial To PC
1 - Serial To PC
2 - Detect a Pulse via Interrupt from a Device
3 - Detect a Pulse via Interrupt from another Device
4 - Status LED 1
5 - Status LED 2
6 - Switch a Mosfet to turn on/turn off Bluetooth Module
7 - Free
8-13 LCD Display
A0-A3 - Foil-Keypad inputs
So in fact, i have only the Pins 7, A4 and A5 free.
For the communication with the Bluetooth-module RN-41, i need 2 Pins, RX and TX and the library "Software Serial" as described here
Now i'm thinking about using the free Pin 7 as TX (Output) and A4 as RX (Input).
But now im wondering, if it would be possible to use A4 and A5 this is SDA/SCL. I think it has to be possible, because I2C does also send and receive, this means one of those pins must be usable as output, or am i wrong?
Pins A0 through A5 can be used as normal digital pins PLUS they can also be used for analogRead(). They are not subject to special limitations (this is something that the arduino documentation and IDE often confuse people about - they should never have called them "analog pins", as the only difference is that they happen to be the ones that can be connected to the ADC - just like how only certain pins can do PWM, or SPI. It's an extra capability)
On principle, I refuse to use "A0" and it's ilk, and just use the numbers...
(A6 and A7 on Atmega328-based boards with the SMD chip (the DIP chip doesn't have those pins), are weird, and can only be used as analog inputs - this is the only case of that weirdness that I've seen in any of Atmel's product line. My theory is they designed the chip as PDIP-28, then when they released TQFP version with 32 pins "hey, let's connect these other pins to the two unused channels of the ADC mux ")
sgt_johnny:
I have the following problem, i use a Atmega328 with Arduino Bootloader, and my pin-list is this:
0 - Serial To PC
1 - Serial To PC
2 - Detect a Pulse via Interrupt from a Device
3 - Detect a Pulse via Interrupt from another Device
4 - Status LED 1
5 - Status LED 2
6 - Switch a Mosfet to turn on/turn off Bluetooth Module
7 - Free
8-13 LCD Display
A0-A3 - Foil-Keypad inputs
So in fact, i have only the Pins 7, A4 and A5 free.
For the communication with the Bluetooth-module RN-41, i need 2 Pins, RX and TX and the library "Software Serial" as described here
Now i'm thinking about using the free Pin 7 as TX (Output) and A4 as RX (Input).
But now im wondering, if it would be possible to use A4 and A5 this is SDA/SCL. I think it has to be possible, because I2C does also send and receive, this means one of those pins must be usable as output, or am i wrong?
you could also change from a nibble mode LCD to an I2C version and free up 8--13.