Due 5V once again

Hi, I am having arduino Due for several days now, but today I've noticed the disclaimer about operating voltage. I would like to clarify some things, please correct me if I am wrong. For temperature sensors or other simple sensors, I should provide current from 3.3V pin, am I right? For 2x16 LCD kits like this: http://nettigo.eu/products/32 I should provide current from 5V, am I right? (I know it from tests only, with 3.3V LCD is very dimmed). How can I know if 5V provided to LCD isn't comming back to any of the pins on board?

Thanks.

You need to supply any attachment with the voltage it needs. However if you LCD needs 5V then you must not connect the status line or any other output line back to the Due.
In theory you should also level shift any logic signal going into any 5V system but most of the time a 3V3 signal is enough although it is out of spec.

How do you know? You must understand exactly what you are connecting. The Due is not a beginners board.

I do not know if this helps but this display works fine with my Due boards:

Connect VCC to Due 5v.

Good luck.

Another thing to be careful of is the max output current spec for the Due - it
varies from pin to pin, you have to read the datasheet for the grisly details
but some pins are limited to abs-max of 3mA if I remember rightly - though others go as
high as 9mA - well you get the picture, its not 40mA or anything likeā€¦

StanO8: I do not know if this helps but this display works fine with my Due boards:

http://www.amazon.com/gp/product/B0080DYTZQ/ref=wms_ohs_product?ie=UTF8&psc=1

Connect VCC to Due 5v.

Good luck.

So, this interface works with the DUE ? http://www.ebay.co.uk/itm/281234403721?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

Why would you think a 5V device will work with the Due?

From Table 46-1, page 1389 of the Atmel doc11057.pdf: http://www.atmel.com/Images/doc11057.pdf

Absolute Maximum Ratings*

Voltage on Input Pins with Respect to Ground................... -0.3V to + 4.0V Maximum Operating Voltage (VDDCORE)............................. 2.0V Maximum Operating Voltage (VDDIO)................................... 4.0V Total DC Output Current on all I/O lines................................ 130 mA

*NOTICE: Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or other conditions beyond those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

Regards, Palliser

topcat36: So, this interface works with the DUE ? http://www.ebay.co.uk/itm/281234403721?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

I am using that interface on a QC2004A 4 line display on both of my Arduino DUE boards. No problems.

I connect VCC to the DUE 5V pin.

Good luck.

And SCL/SDA directly to Pins 20 and 21 ? I measured the 2 pins from the interface, while powered from 5V and they have 5V each to GND.

This Diskussion is raising question marks in my mind: I have a Ethernet shield which oft course is based on 5V operation. The communication is based in SPI. What happens, if I directly plug the shield to my Due without using level shifters? Will the shield destroy my Due?

topcat36: And SCL/SDA directly to Pins 20 and 21 ? I measured the 2 pins from the interface, while powered from 5V and they have 5V each to GND.

You should level shift the voltage levels from the 5V gadget to the DUE's 3V level.

There are chips specifically designed to do this for you. It is the Right Thing To Do.

There is a possibility of your 5V gadget working fine with the I2C lines operating at 3V. If you can remove any pull-up resistors on the gadget's I2C lines (I2C lines are supposed to be open-collector), and use only the existing pull-ups on the DUE (which are tied to 3V), then that may be a working, however marginal, solution. You'll need to read the datasheets very carefully to see if the voltage thresholds are compatible. There have been numerous discussions on this already on this forum (do some searching).

If your gadget does not have pull-up resistors (and its I2C lines are configured as push-pull), then your gadget has an improperly designed I2C interface, and its designers should be flogged.

Running the DUE with the I2C lines pulled to 5V may work - for a while. However, this condition is out-of-spec, and may destroy the IO on the SAM chip. Then all you'll have is a dead DUE.

Good luck,

Chris