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1  Products / Arduino Due / Re: Bill Of Materials (BOM) required for Arduino DUE on: April 18, 2014, 07:36:31 am
The attached was generated from the default import of:
http://forum.arduino.cc/index.php?topic=146574.0

No guaranty of accuracy.  None at all.

Maybe somebody else has a validated list...

-Chris
2  Products / Arduino Due / Re: Using Analog Reference on: April 18, 2014, 07:26:15 am
Hi Ryan,

I have never played around with this.  However, when I was working on this:

http://forum.arduino.cc/index.php?topic=146574.0

I added the notes in the attached picture Capture.png.

Component highlighed in Capture1.png.

Why would they do this?:  It makes the board easier to use (consider the market).  Also, Vref can only get smaller than this current value.  By fixing it on the board, I suspect that they hoped to reduce failures due to folks applying 5V, and the like.

Regards,

-Chris
3  Products / Arduino Due / Re: impossible to use I2c display on: April 10, 2014, 07:52:01 am
motodaddo,

Please provide a schematic that accurately represents all of your circuit (relay too).

In particular, there are surge suppression tricks when switching relays on/off that could cause some problems.

-Chris
4  Products / Arduino Due / Re: Arduino DUE Connect to PC & COM Ports on: April 09, 2014, 03:06:43 pm
Dennis,

In short: yes.

However, look at this if you need to manage more...
http://forum.arduino.cc/index.php?topic=187831.0

-Chris
5  Products / Arduino Due / Re: i2c + DUE don't talk!! on: March 17, 2014, 12:08:24 pm
I2C works with me , unless you need to use the error returns form Wire.endTransmission(), But the main part works .
Yes... If I remember correctly, anything that relies on a NACK detection will fail.  NACK is not only used by the I2C spec as a means to detect an address that is not responding, but it is also used for certain protocols (like repeated starts..).  This is not as unusual as it sounds (many ADC's and DAC's use this type of protocol).  One simply must check the datasheets carefully to see what's required by your I2C device.

So, we're currently in a situation where some I2C devices work on most other flavors of Arduino's, but perhaps not on the DUE.  This is where much of the confusion over I2C with the DUE comes from.

So, simply saying that the wire library works, or doesn't, isn't enough.  The I2C protocol is just not fully supported with the current default library for the DUE.  This is not necessarily an awful thing.  However, it can be disappointing (and a little warning would have been nice).

-Chris
6  Products / Arduino Due / Re: i2c + DUE don't talk!! on: March 17, 2014, 10:24:41 am
That is why I indicated in my last post that Wire is broken on DUE.  It is possible other folks are not running into the same issues.     

If I can chime in here... I2C on the DUE is not exactly broken... It's just not complete.  The way that the SAM chip handles the I2C registers (at the hardware level) is different than the other Arduino's.  This breaks some of the default functionality of the Wire library.

I suspect that it became too much work (with too little time) to make the entire default library work, so they hobbled it, to make it function at a very basic level (with no warnings about its short-comings).

The end-result: one needs to dig a bit to determine if the I2C hardware that they wish to use will work with the lame default wire library.  Some will work, some will not.  These limitations have been listed, discussed, and fixed by members of/in the forum.

However, I believe that the default & official wire library has still not been updated.

The ghosts, my friends, are in the details.

Regards,

Chris
7  Products / Arduino Due / Re: i2c + DUE don't talk!! on: March 10, 2014, 01:33:22 pm
psycho82,

I2CScanner does not work with the DUE.  Search this forum for alternatives.

Also, there's a big warning about the GY-521 I2C pull-ups.  
http://playground.arduino.cc/Main/MPU-6050#
Be careful with low-valued pull-up resistors and the DUE board, as it's easy to burn up the DIO.  The DUE already has 1k pull-ups on the I2C lines.

Good luck,

Chris
8  Products / Arduino Due / Re: Adafruit SSD1306 128x32 OLED, I2C pull up resistors? on: March 07, 2014, 10:34:04 am
conradelektro,

It looks like the adafruit board has 10k pullups (see attached pic).
Sourced from:
https://github.com/adafruit/Adafruit-128x32-I2C-OLED-Breakout-PCB

It might be easier to remove those instead.

If you don't remove any resistors, the net effect would be a 4mA pulldown current.  This is still in-spec for the SAM chip (source 3mA, sink 6mA).  It's just unnecessarily stressful.

I have never used this board.

-Chris
9  Products / Arduino Due / Re: I2C (Wire) pull up resistors, Arduino Due, 20 (SDA0-3), 21 (SCL0-3) on: March 06, 2014, 01:59:48 pm
My question: Where are these 1 K pull up resistors (RN5D and RN5C) on the Arduino Due board? I might try to remove them.

As you might guess from their designators, RN5D and RN5C are part of a resistor array.  Fortunately, they are the only two resistors used in the array (the rest are not connected), so it's ok to remove the whole thing.

See the attached pic for location.

I always remove them (with hot tweezers).

Regards

Chris
10  Products / Arduino Due / Re: I2C (Wire) pull up resistors, Arduino Due, 20 (SDA0-3), 21 (SCL0-3) on: March 05, 2014, 08:36:01 am
Conrad,
Is it true that I do not need additional pull up resistors if I connect an I2C slave to pins 20 (SDA0-3), 21 (SCL0-3) of the Arduino Due? (On the Arduino Due schematics it is noted as "I2C Voltage Translator".)
Yes.  You do not need to add (nor should you) any additional pull-ups anywhere in this I2C bus.  The resistors on the DUE are very aggressively sized (small).  Adding any additional pull-ups on the I2C bus could destroy these IO pins.  Also, the last time I checked, the print says that they are 1.5k pull-ups.  However, in reality, 1k pullups are installed on the PCB (double check to be sure).

Quote
If I use the Wire-Library the I2C communication is via pins 20 and 21 ?
Yes.

Quote
How do I do (which library) I2C communication via pins 9 (SDA1 = TWD0)  and 10  (SCL1 = TWCK0) ? There are no pull up resistors for pin 9 and 10?
It's the same wire library.  Do a quick search for "wire1" for solutions.  Also, become familiar with the limitations of the current wire library, as many of the lower-level (more advanced) routines still do not work.

In addition, yes, you will need to add external pull-ups for SDA1/SCL1.

Good luck!

-Chris
11  Products / Arduino Due / Re: Arduino Due on: March 04, 2014, 10:46:19 am
TopCat36,

Please consider adding a series resistor to Pin53.  This will add a bit of protection from the 3.3V line if some user inadvertently sets Pin 53 as an output.

A simple series resistor here could save the whole chip (and not affect the operation of your circuit in any way).

-Chris


12  Products / Arduino Due / Re: Due 5V once again on: March 04, 2014, 10:39:21 am
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
13  Products / Arduino Due / Re: reset pin pull up ? if yes , only 3.3V? on: February 14, 2014, 05:29:06 pm
I see, diode keep voltage level equal to forward voltage....
Yes.
Quote
Does schematic you posted work well with Due?
Means is voltage treshold low enough?
I don't know. 
You would need to look at the datasheet for the SAM3 micro on the DUE, as well as the ATMEGA16U2 chip (because the reset line runs there as well - see attached schematic) for the reset pins specs.  I believe that in addition to the on-board 100k pull-up on the DUE pcb, the Sam3X has an internal 15k pull-up on this line as well.  I do not know the internal setup, or requirements, for the ATMEGA chip.
Quote
It would be pretty useful for my app,however I can('t) see pullup in the circuit you posted.
Question is also, is that pull up resistor essential? If yes, desired value would be 10k?
On the DUE side, you would not need to add any additional pull-ups, because they already exist on the DUE's pcb.
In any case, ~10k-15k is a typical pull-up value in this role.
As far as I can tell, you won't hurt anything on the DUE; and it will either work, or not work...

Good luck,

-Chris
14  Products / Arduino Due / Re: Is I2C working correctly on 1.5.5?? on: February 14, 2014, 01:50:41 pm
I just pretend to be a programmer (I'm actually a EE, the most dangerous type of coder).  

It is my sincere belief that the skills of the Arduino team far surpass my own.

In addition, this DUE project of mine is on indefinite-hold.  Testing any code at this moment is not possible.

-Chris
15  Products / Arduino Due / Re: reset pin pull up ? if yes , only 3.3V? on: February 14, 2014, 01:44:02 pm
The "forward voltage" of the diode must be less than the requirements for the "low voltage threshold" on the reset input.

The forward voltage on any-old-diode may be near a 1 volt (~0.7V).  A Schottky will be less (often ~0.3V).  However, Schottky's can have a higher "leakage current" that sometimes you need to deal with.

See attached picture.

-Chris




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