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Topic: Using pins A6, A7 on pro Mini compatible (Read 6429 times) previous topic - next topic


I have this: http://www.ebay.com/itm/Meduino-Pro-mini-Enhancement-3-3-5V-adjustable-16MHz-MEGA168-Arduino-compatible-/150884671106?pt=LH_DefaultDomain_0&hash=item23216d5e82

and I am using this simple sketch to sequentially turn on and off eight LEDs  attached to analog pins A0-A7 :
Code: [Select]
int timer = 25;           // The higher the number, the slower the timing.

void setup() {
  // use a for loop to initialize each pin as an output:
  for (int thisPin = A0; thisPin <= A7; thisPin++)  {
    pinMode(thisPin, OUTPUT);     

void loop() {
  // loop from the lowest pin to the highest:
  for (int thisPin = A0; thisPin <= A7; thisPin++) {
    // turn the pin on:
    digitalWrite(thisPin, HIGH);   
    // turn the pin off:
    digitalWrite(thisPin, LOW);   

  // loop from the highest pin to the lowest:
  for (int thisPin = A7; thisPin >= A0; thisPin--) {
    // turn the pin on:
    digitalWrite(thisPin, HIGH);
    // turn the pin off:
    digitalWrite(thisPin, LOW);

but the LEDs attached to pins A6 and A7 never turn on. My question is: do i need to do some sort of configuration to use analog pins 6 and 7


Looks like nice version of the promini, breaking out all the pins.

A6 & A7 are analog input only. You cannot digital write to them.

If you want extra IO, I have a '1284 board with 32 IO.
$3 for a  bare board mailed to you.  No onboarrd regulator, power it from 4.5V or 4.8V battery pack.
We can discuss if you want one assembled. Not really set up for that yet, did this one by hand, waiting on some parts so I can try a reflow oven controller.

Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.


Nice job.  Did you use solder paste and an oven for the surface-mount components?


Aug 29, 2012, 07:41 pm Last Edit: Aug 29, 2012, 08:07 pm by seanz2003 Reason: 1
Thanks for the info Crossroads and I will definitely keep your board in mind for a future project. currently, I want to build a 4x4 led cube using as few parts as possible. with 22 io pins (14 digital, 8 analog) I thought the pro mini would work just fine to drive 16 anode columns and 4 cathode levels (with 2n2222 transistors).  I failed to consider that digital pins 0 and 1 are for communication, and now I learn that A6 &A7 are input only. So it looks like I must use shift registers. Right now, I have it working with the cathodes connected directly to ground but I would like to be able to control levels as well to increase the complexity (and learning).


No, this particular one we used a stencil to apply paste for the uC, hot air rework station, and then soldering iron for the ground pins that the hot air couldn't seem to do. Everything else was just soldering iron.  I have some parts on order to turn a 1500W toaster over ($50 on sale at Target) into a reflow oven.
(I should check on those has been a while since I ordered them.)

4x4x4 is 64 LEDs, yes? So arrange your IO a little.
Drive 8 anodes, drive 8 columns of cathodes - vs 16 anodes and 4 columns of cathodes.
Now you're down to 16 pins.
Instead of 16 transistors, use a TPIC6B595 shift register with high current sink - and Output Enable!
3 control lines, and a PWM to drive OE/ for brightness control.
Down to 12 pins used and 1 external part, 8 current limit resistors on the anodes.

I think this example uses 2 shift registers - you can drive anodes directly, and replace the bottom shift/current buffer with TPIC6B595.
Or use 8 transistors like you started with, add a 9th between all emitters & gnd driven by PWM for brightness.
17 IO then, serial Rx/Tx still, and maybe read a pot to create PWM level to be used, if its not sent in from serial.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

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