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1  Using Arduino / Microcontrollers / Re: bootloading the atmega328-pu on: May 31, 2012, 06:39:26 am
Not the need for, just the size of.  At higher speeds you need smaller caps to be able to react fast enough to do their job.
2  Topics / Product Design / Re: How to design a PCB that allows firmware updates. on: March 03, 2012, 01:42:42 am
Getting an SD capable bootloader is probably one of the best if you can spare the 2k for the boot loader.  I don't know of any off hand but I know I've seen some of the guys here starting to think about one recently.

The BootDrive is a nice option as well, leaving the stock bootloader on the micro and emulating AVRDude talking over the serial line.

For my own project I used a 2nd micro controller similar to the BootDrive, but I'm directly SPI programming my main chip, removing the need for a bootloader entirely and allowing faster communication between the two devices.  I get around needing 2 SD cards or switching between them by talking through my  updating micro controller to the same card that it reads to update the main controller.  It impacts throughput significantly, but should also reduce write latency at the same time.  If you're interested in perusing this option I can link you my code and schematics, but they are very early in development.
3  Using Arduino / Programming Questions / Re: 28k+ sketch and SD calls reset arduino on: March 02, 2012, 10:46:31 pm
The SRAM requirements for SDfat are not insignificant either.  The library requires 512 bytes of ram just for cache alone, so if you're using anywhere near 1.5k of SRAM before you add in the SD library then expect to have problems.
4  Using Arduino / Project Guidance / Re: Motorcycle HUD on: February 20, 2012, 08:41:35 pm
Do you have any more information on the display you used?  Micro optics and micro display are getting lost in a sea of generic search results.
5  Development / Other Software Development / Re: Fast alternative to digitalRead/digitalWrite on: February 19, 2012, 06:23:41 pm
If you include both SdFat and DigitalPin in the same program you get a redefinition of 'struct pin_map_t' error
6  Using Arduino / Networking, Protocols, and Devices / Re: SPI.transfer rotates bytes? on: February 19, 2012, 05:55:19 pm
Do you have the correct SPI mode set for your device?  Just a shot in the dark there.

The SPI "library" in .22 is just an incredibly simple wrapper for a handful of commands.  I haven't looked at the new IDE yet, but how much different is it really?
7  Using Arduino / Networking, Protocols, and Devices / Re: SPI library questions: API vs. implementation details on: February 19, 2012, 05:50:10 pm
SPI.transfer works only with a single byte at a time.  setBitOrder will transmit the bits of that byte in the requested order, if the value you are sending is more than one byte long it is up to you to transmit the bytes in the correct order.

The setDataMode modes are for clock polarity and phase.  While I haven't looked at your datasheet I don't see any way that they can be related, since you must already be communicating with the correct polarity and phase in order to transmit data to your device in the first place.  They must be modes specific to the operation of the DAC.
8  Using Arduino / General Electronics / Re: usb cables: what is this part? on: February 05, 2012, 08:28:40 pm
A balun (which is a transformer to convert balanced/unbalanced signals) has nothing to do with ferrite beads
9  Development / Suggestions for the Arduino Project / Re: LiquidCrystal library documentation on: February 04, 2012, 05:35:49 pm
The buffer is in the LCD controller, the library does nothing but relay your commands and parameters to the controller.  If you want to write to a fixed location on screen after scrolling the display from Home then you need to either track how much it's scrolled and offset your cursor, or just maintain your own buffers and scrolling code and overwrite the entire display every refresh.
10  Using Arduino / Project Guidance / Re: Arduino as a webcam.... on: February 03, 2012, 10:40:33 pm
If you make no attempt to understand the elements of a problem, then the answer will be confusing.  You can't think of entire devices as just magic black boxes that :do stuff:

A simple train of thought:

How much bandwith does a raw video stream take up?  Well we've got to look it up.  10 seconds in google tells us: aprox 20MB per second

How much bandwith does a regular USB device have available?  Well we've got to look that up too, back to google.  In high speed mode about 1.4MB per second

Well, that's pretty cut and dry right there, so no, you cannot stream "video" directly over USB, not even close.  Well "magic box" does, so how do they do it?  Well what ways off the top of your head can you think of to fit 20MB of data down a 1.4MB pipe.

You could capture at 2 FPS (not what they're doing)
You could capture at 72x48 resolution (also not what they're doing)
You could compress the data (!)

Hmm... realtime video compression, all of a sudden that is starting to sound a lot like reasonably heavy "processing and memory storing".

And that's just thinking about the USB transport alone, not with emulating a webcam device, or digitizing the video signal, or even just transmitting the data (can an Arduino transmit 1mbps? 12mbps? 480mbps?)


I have an SD card that can store 2 gig of data, and yet I'm told that my Arduino can only hold 2k of data.  This confuses me, obviously I'm looking at a smaller device that can hold way more data so why doesn't it make sense?  

Well the answer is that an SD card and an Arduino are entirely different devices, with entirely different capabilities, built for entirely different purposes.  Comparing a USB video capture device, or an Atom laptop (which is something like 2 orders of magnitude faster, and chocked full of specialized, dedicated hardware) with an Arduino is just as crazy a comparison.

Meantime you have yet to explain why it works on the $55 dongle.
You get more intelligent and far less condescending answers if you attempt to understand even just the question yourself.  Don't expect the information to just flood out of the screen at you if all you're willing to do is throw up your hands and say "I dunno"
11  Using Arduino / Project Guidance / Re: Arduino as a webcam.... on: February 03, 2012, 07:32:54 pm
Well I really doubt that the internals of the honestech box is any more than an arduino.

Electronic devices are far more than just micro controllers and resistors.  There are tens of thousands of dedicated chips that are extremely specialized to perform certain tasks.  Much in the same way that your video card vastly outperforms the general purpose processor in your computer that's clocked at even 4x the speed for the purposes of rendering 3d graphics, there are dedicated chips that are made that are smaller and cheaper than an Atmega that do specific tasks that the Atmega can only dream about.

Video and audio processing onboard the Arudino, as well as webcam stuff has been asked about frequently enough in the past, and there are extremely fundamental reasons why it is laughably unfeasible.  Its been explained far better in the past than I could, so if you want to read more why I would recommend digging up some of those old threads.
12  Using Arduino / Project Guidance / Re: Controlling Multiple Pins at the same time on: February 03, 2012, 12:11:45 am
I would be especially interested to know because I'm doing fast logic-controlled switching and true simultaneity would be a small but non-trivial performance increase.

You might be surprised (at least I was)  Obviously it depends on specifically what you're doing, but for instance converting the LiquidCrystal library to use a fastDigitalWrite variant alone gains 30% performance improvement.  Changing the fastDigitalWrites to direct port manipulation only increases performance an additional 0.06% from there.
13  Using Arduino / Storage / Re: Powering MicroSD with Digital Pins on: February 02, 2012, 06:45:28 am
I've read of some cards needing just over 100ma when starting up, so no a digital pin is not going to source anywhere near that much current.  If you're reading 35ma that already is very near to the pins maximum rated current.  If the cards built in low power mode is not good enough for you I would throw it on a transistor.
14  Using Arduino / Project Guidance / Re: Controlling Multiple Pins at the same time on: February 02, 2012, 12:48:07 am
if you don't want to write out the for loop everywhere you can just make your own function that takes an array and pin mode and does the loop.
15  Using Arduino / Project Guidance / Re: When to use which wiring.c files on: February 02, 2012, 12:43:16 am
What are you expecting to gain with your 4 cycles per loop?  You're going to spend far far longer waiting on the A/D each time than you'll spend testing the loop condition.
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