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1  Using Arduino / Installation & Troubleshooting / Leonardo mounting problems on: January 12, 2014, 02:50:02 am
My Leonardo suddenly stopped mounting on any of my computers.  I was working with it, uploading sketches just fine, then during one of those uploads, it reset, the computer made the disconnect noise, and it never came back.  Now when I plug it in, the computer first makes the USB insertion noise, and I can see it show up under Ports in my Control Panel.  It has the glowing light on it and after a few seconds it turns into a solid green light.  However at the same time, the computer makes the disconnect noise and it disappears from the Ports list, basically as if I disconnected it.  I tried it on several computers and they all do the same thing, it shows up briefly, then disconnects.

What could be causing this and is there something I can do assuming it's not fried?
2  Products / Arduino Due / Interrupt 4 on a Leonardo on: November 12, 2013, 06:10:47 am
I know this forum is for the Due, but I don't know where to report problems with the IDE itself.

I'm using a Leonardo board and I noticed when I use version 1.5.2, and try the test code on the attachInterrupt web page (and changing the interrupt to 4 instead of 0), it doesn't work.  The sketch compiles and uploads fine, however it doesn't work.

If I use version 1.0.5, it works and the interrupt does what it's supposed to do.

I realize 1.5.x is primarily meant for Due support, but if it's meant to some day replace the 1.0.x version, backwards compatibility needs to work.  So I'd file this under bugs.
3  Using Arduino / General Electronics / Re: Switching between I2C and SPI on: November 11, 2013, 02:57:20 pm
True, no device knows about an Arduino, or RPi, or MS430.  However, they do know whatever pins they need for communication, just like any controller also knows it's own pins for whatever bus.

The datasheet clearly explains how to wire it up for either SPI 4-wire, SPI 3-wire, or I2C.  Knowing that, and knowing the different pins on whatever controller, including Arduino, you get the pin mapping I provided above.

However, it makes absolutely no difference what controller is being used, not for the purpose of my question.  I could've just as easily said it's being connected to pins John, David, and Paul in one configuration and John, David, Paul, and Matthew in another.  All I wanted to know was if there is a way to mechanically configure which configuration it's using.

But it's obvious to me that I'm way too dumb for the likes of JamesCS4.  So I thank you for wasting my time, sorry for having wasted yours.  I already got my answer elsewhere with the same exact  original post.  Thanks for reminding me why I stopped using these forums.
4  Using Arduino / General Electronics / Re: Switching between I2C and SPI on: November 11, 2013, 11:38:34 am
Data sheet.  It can also be configured as a 3-wire SPI device but I'm not interested in that.  Just the 4-wire setup or I2C.
5  Using Arduino / General Electronics / Switching between I2C and SPI on: November 11, 2013, 04:43:06 am
I'm working on a design that incorporates an ADXL345 accelerometer.  It's able to work either through I2C or SPI.  What I'm trying to figure out is if there is a way to make that selectable by the end-user, perhaps by means of setting a jumper.  For example, if the user wants to use the accelerometer as an I2C device they set a jumper or if they want to use it as an SPI device, they don't set the jumper (or move it between three pins, so that when pin 1 and 2 are shorted it's in one mode and when pins 2 and 3 are shorted, it's in the other.)

Note, this is *not* meant to be a running change.  It's meant to be configured prior to turning the whole unit on and programming it.  So is there some way to do this?  Some way to switch how it communicates?

Relevant info on the ADXL345:
For SPI communications (4-wire), the pins are wired as follows:
Quote
CS (pin 7) -> Arduino SS
SDI (pin 13) -> Arduino MOSI
SDO (pin 12) -> Arduino MISO
SCLK (pin 14) -> Arduino SCK

For I2C communications, the pins are wired as follows:
Quote
CS (pin 7) -> VCC
SDA (pin 13) -> Arduino SDA
SCL (pin 14) -> Arduino SCL

Notice how in both setups, pins 7, 13, and 14 are used.  If pin 7 is tied to VCC, the device will be in I2C mode, and if it's tied to SS, it'll work in SPI (4-wire) mode.

I can probably do this with a mechanical switch, but I'm hoping for a simpler (for the end-user) method, just using a jumper to switch things around.  Much like there are some devices out there that have a jumper on them to switch between 3.3V or 5V operations.

So, help anyone?  Schematic?  Parts (if any)?
6  Using Arduino / LEDs and Multiplexing / Re: LED HULAHOOP... err... on: September 04, 2013, 02:32:05 pm
I use the FastSPI_LED library exclusively.  Yes I have tried Adafruit's library, as well as other methods of working with different drivers.  FastSPI_LED is by far the best and fastest one.  Now, that's not to say the others aren't worth their salt.  Each one had its purpose.  The end-user needs to decide what works best for them.  For all of my LED projects, I stick with FastSPI_LED, from simple pattern generating along a string to high speed POV displays.
7  Using Arduino / General Electronics / Re: Transistor + MOSFET high side switch on: August 12, 2013, 08:25:34 am
No can do.  This is a custom design and it needs to fit inside of a 7/8" diameter tube.  I have about 2.5" of length to work with, stacking two PCBs to accommodate everything (AVR, micro SD, USB connector, buck/boost circuit, battery charging circuit, all supporting bits and pieces of components).
8  Using Arduino / General Electronics / Re: PCB construction Time lapse on: August 11, 2013, 06:52:36 pm
Link doesn't work for two reasons:

a) you have quotes around the URL
b) you missed the ':' after 'http'
9  Using Arduino / General Electronics / Re: Transistor + MOSFET high side switch on: August 11, 2013, 06:50:40 pm
Gotcha.  I used the symbol the Adafruit library had for a P-Channel MOSFET.  I see that Sparkfun's symbol is a closer match to what you posted above.
10  Using Arduino / General Electronics / Re: Transistor + MOSFET high side switch on: August 11, 2013, 06:11:50 pm
How do you not figure?
If one channel draws 860mA (let's not split hairs) at 100% then it draws 860mA at 10%, too.

Yeah, I know that.  But the string won't always be at that ~2.6A.  If I light up one channel only, it will only draw 1/3 of that.

However, as far as the duty cycle is concerned, you are correct, whether it's 100% or 10%, the peak draw is always the same.

What I'm seeing is probably more of an average draw at anything less than 100% duty cycle, likely because my DMM can't keep up with the duty cycle.
11  Using Arduino / General Electronics / Re: Transistor + MOSFET high side switch on: August 11, 2013, 05:00:15 pm
Yeah, I need a logic 1 to turn it ON.  What happens when the unit resets and the pin is tri-stated?
EDIT: some how I missed your circuit diagram all together. It shouldn't actually matter if the NPN transistors base is left floating as no current will flow into the base so the transistor *should* switch off, then your resistor on the gate of the FET to the supply voltage will turn the FET off by discharging the gate.
However, adding a large pull down resistor (~100k) to the base of the NPN won't do any harm, and will ensure that the transistor is switched off when the pin is tristate.

Tom, would you mind drafting up a schematic for that?
12  Using Arduino / General Electronics / Re: Transistor + MOSFET high side switch on: August 11, 2013, 04:59:02 pm
the LED string tops out at 2.54A when at 100% duty cycle.
It's 2.54A all of the time (at any time) it's on (low duty or high duty).

How do you figure that?  It's an RGB string, and if only one channel is on, at full 100%, that's only 0.864A.  Worse if I'm only driving a few of the LEDs as opposed to the full string.  So how do you figure it's always at 2.592A?  (My typo, that should've read 2.592A in my previous post.)
13  Using Arduino / General Electronics / Re: Transistor + MOSFET high side switch on: August 11, 2013, 04:06:17 pm
The critical value to look at is the RDS_ON of the FET when it is switched on at your target voltage (VGS).  For a 3.3V system you'd be looking at VGS = -3.3V, for 5V VGS = -5V.  You want that resistance to be as low as possible to reduce losses.

So you want to be looking for a logic-level P-channel MOSFET (IRLxxxx for example).

I knew I forgot something.  It needs to be able to drive about 3A as the LED string tops out at 2.54A when at 100% duty cycle.  So I'll have to hunt for some of those.  Does it matter if the values are larger than what the circuit is running at?

As for the NPN, that is much less critical.  It's basically working as a simple inverter - you provide a logic 1 and it switches on connecting the gate of the FET to ground.  If you're switching the same voltages as you're driving the switching with you don't really need it, but it's convenient to keep it as otherwise a logic 1 would turn OFF the circuit rather then ON.

Yeah, I need a logic 1 to turn it ON.  What happens when the unit resets and the pin is tri-stated?
14  Using Arduino / General Electronics / Transistor + MOSFET high side switch on: August 11, 2013, 03:37:28 pm
After doing some research, I found the attached schematic to make a high-side switch.  However, this was designed for a 12V system, whereas I'm working with 3.3V (or 5V *) voltages.  Also, I've never used FETs before, so I have a few questions:

a) How do I determine what transistor and P-channel MOSFET I need to look for.  I have zero, none, no idea what I need to look for as far as specs.
b) How do I determine what the various resistors need to be?  I'm assuming they are related to what the transistor and MOSFET need, but as with point (a), I don't know how to figure those out.

The idea here is that I will be switching the 3.3V (or 5V *) voltage that feeds the 4-pin connector that goes to the LED string.  It's literally going to act as if it's a mechanical ON/OFF switch, so no high frequency toggling.

* I'm still trying to determine whether I want to run this system at 3.3V or 5V and I am going to start a different thread with the design and questions.

(Decided to stick with only 5V)
15  Using Arduino / General Electronics / Re: Problems with a MOSFET relay on: August 09, 2013, 11:05:34 am
The other side of those signal lines is connected to a live circuit though, ie the AVR which is powered up.  I don't want the possibility of back feeding VCC back into it.
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