Question about Voltage on I/O pins

Sorry for being dumb as a moonbat, but.....can I connect a stepper motor driver that drives a 5v motor to pins 10,11,12,13 IF I power the driver board separately, AND the DUE with a power supply? I have some mental block that won't let me see this answer. Thanks...

[quoteSorry for being dumb as a moonbat, but.....can I connect a stepper motor driver that drives a 5v motor to pins 10,11,12,13 IF I power the driver board separately, AND the DUE with a power supply? I have some mental block that won't let me see this answer.][/quote]

That depends so much on the motor drive you plan to use. Should you power it directly from the DUE? No. You want an actual "stepper drive" so you don't have switch the windings in code or worry about keeping the correct current. Have a look at this:

You will note in the specs this driver will accept 2.5V for a logical "1". Since the DUE's outputs go to almost 3.3v you should be fine.

Thanks much, metzner 49. Appreciate it very much!

JOe Walburn

The I/Os on the Due are NOT 5V-compatible! Connecting any 5V device directly to Due pins is likely to damage the Due. Since the stepper driver signals will be output-only from the Due, the safest thing to do is buffer them, using 3.3V-to-5V level-shifters to protect both devices. Depending on the input circuitry of the stepper driver, you might be able to get away with simple series resistors (about 330 ohms), but that will depend very much on the signal requirements of the stepper driver.

Regards,
Ray L.

Thanks much, R.L. I imagine there are a number of other newbs on this forum who have similar questions but are afraid to ask. Well, not me. So let me ask you this: Why would Arduino build a board, as the Due, with so many features, yet with output voltage limits so low as to make standard accessories unusable???? It just doesn't make sense.....at least to this newb. If you can shed any light on that question I'd be very grateful. And the fixes which you so kindly proposed sound good, but there was still some question as to the safety of both the Due and the stepper motor.

Once again, I thank you for your help. I've read tons of relevant material but still this just doesn't make sense.

Respectfully,
Joe W

Arduino Due is pin-wise a breakout board for the SAM3X8E ARM Cortex-M3 CPU. So Due has the same voltage and current limitations on the pins as the CPU. The “standard accessory” as you mention is a standard accessory for Arduino Uno and alike (non-ARM boards). Due came to market much later (I think a few years later) than Uno so most of the shield designs were made to fit Uno and it’s 5V. Although some of the shields for Uno work with Due as well (like the Ethernet shield). So if you are searching for some “standard accessory”, make sure it’s Due compatible :slight_smile: Btw. 5V is not always the better choice. For example the majority of LCD displays is 3.3V so you have to use some external circuitry to drive them from Uno.

Also note that some Due pins can only source or sink 3mA, so can't even drive
opto-isolators, so interfacing can be tricky. I'd suggest using 74HCT14's(*) to boost
3.3V signals to 5V. For input the 74LCX family (IIRC) are 5V tolerant on the inputs
but run at 3.3V and output 3.3V.

(*) or any suitable gate from the HCT familty (not HC family, has to be HCT)