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16  Using Arduino / Displays / Re: Sparkfun LCD, ok without backlight, or in sunlight? on: October 04, 2012, 02:30:27 pm
I don't know if your white-on-black is similar to my white-on-blue but for my case, I had to keep back light on all the time indoors. But if I turned off the back light, I can see outdoors. I had to readjust the contrast a bit though.
Thanks. I haven't messed with the contrast outdoors with the backlight off. I'll give that a try.



Also, a friend of mine said he flipped the polarizing screen on some LCD's to get the negative LCD image. Has anyone tried that on these LCD displays?  Will it turn my white-on-black into a black-on-white LCD?  It looks like it will come apart easily with a few metal tabs.
17  Using Arduino / Displays / Re: Sparkfun LCD, ok without backlight, or in sunlight? on: October 04, 2012, 01:19:29 pm
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Can I use it with no backlight?  And is it easily readable in bright sunlight?

You can experiment since you already have one. Generally, the positive types (lights going through the pixels, like white-on-blue) don't work without backlight. The negatives (reflective. lights got blocked by the pixels) work without backlight.

I don't have the black-on-green.  I only have the white-on-black, which is basically not readable at all without backlight.  I am asking if the black-on-green will work with little to no backlight.  From what you are saying, it will, thanks.

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Or does anyone know of a good, reflective LCD display that is serial-enabled for Arduino?

Parralex (?) has them. and I am sure New Heaven has them too. However, they are generally quite expensive and it makes more sense (and more fun) to program an avr that functions like a serializer.

The ones at parallax look to be very similar to the Sparkfun models, and basically about the same price.

The ones at New Haven also look similar, and maybe slightly cheaper. However, it looks like they are mostly (if not all) RS232 as opposed to TTL. I assume they can run on TTL signal voltages (in RS232 data format). I have an RS232 output algorithm for VFD's, but it would be nice to simply plug and play using the serial library for fast/dirty projects, without re-inventing the wheel. 

Does anyone know whether one brand or the other works better with no backlight and/or in direct sunlight?
18  Using Arduino / Displays / Sparkfun LCD, ok without backlight, or in sunlight? on: October 04, 2012, 11:16:09 am
Hi all,
I have the Sparkfun 16x2 white-on-black LCD and it works ok, but must always use the backlight. It's also no great on sunny days.

I'm looking for a purely reflective type LCD, or at least one that will work great in sunlight. It would be nice to save on battery power by not using a backlight.

My question are: Does the Sparkfun black-on-green, 16x2, LCD work more like a reflective type (more than the white-on-black one)?  Can I use it with no backlight?  And is it easily readable in bright sunlight?

Or does anyone know of a good, reflective LCD display that is serial-enabled for Arduino?

Thanks in advance.
19  Using Arduino / Interfacing w/ Software on the Computer / Re: Anyone familiar with Hyperterminal? on: February 05, 2012, 02:04:42 pm
Alright, thanks for the replies. 
20  Using Arduino / Interfacing w/ Software on the Computer / Anyone familiar with Hyperterminal? on: February 04, 2012, 06:44:22 pm
I'm transmitting binary (in single 8-bit bytes) out of the Arduino and receiving the data on a PC.  If I use Qbasic to receive the data, it comes out as expected.

When I use Hyperterminal, it is interpreting the data as text and altering it accordingly (adding null characters etc. ). 

Is there a way to make Hyperterminal capture the data stream as raw bytes, and not alter it at all?

There are many options in Hyperterminal and I didn't want to have to play with each and every one.
21  Using Arduino / Storage / Re: sdfat vs. sd on: February 03, 2012, 03:11:16 pm
Well, I can definitely confirm SDfat is much faster than SD.h.  I was saving somewhere around 14 samples per second using SD.h, but with SDfat I'm somewhere around 500 per second.  There may be a case of apples-to-oranges since I'm not sure I was saving the same thing in both situations, but the difference is still amazing.  I have a few questions about reading with SDfat, but I'll have to organize my questions better before asking.

SDfat is a project-saver, fat16lib! Thanks! 
22  Using Arduino / Storage / Re: Fast serial to SD card data logger on: January 29, 2012, 10:24:05 pm
Right, that's what I calculated. So how would I get 1.4Mbit/sec on 115K baud?
23  Using Arduino / Storage / Re: Fast serial to SD card data logger on: January 25, 2012, 08:50:39 pm
115,200 is fast enough to do dual 16 bit stereo at 44.1K samplling each side, that's what I'm after, my own digital sampler.
That would be nice. Just curious... how do you figure that?
24  Using Arduino / Storage / Re: Has anyone timed how long it takes to write 2 bytes using the SD library? on: October 21, 2011, 01:53:50 pm
Thanks for all of the replies.  So it looks like there are a lot of options with a wide range of speeds. 

My plan was to wire the card myself just using the resistor dividers as described.  As far as what library to use, I guess I'll just experiment with a few and see what I get. 

At least it seems one way or another, it should be able to do most of what I want.

Is there an inexpensive shield or other hardware that will make it significantly faster than just wiring the SD card directly to the Arduino?  Or is the resistor divider method about the same, as say, the Ethernet Shield?  (Using one of the common SD libraries.)
25  Using Arduino / Storage / Has anyone timed how long it takes to write 2 bytes using the SD library? on: October 19, 2011, 06:12:07 pm
Just trying to determine if this will be fast enough for what i want to do. 
Up til now, I've been just writing to memory and serial-transferring to a laptop.  Obviously that means I can only log a small amount of data, then it has to stop while transferring the data to the laptop.  I end up with small, discrete chunks of data.

In order to get a large, continuous chunk of data, I've been considereing storage onto an SD card, but in all of my searches, I can't find any info on how long it would take to log 2 bytes of data. (Or even one byte.)

I assume SPI is faster than transferring at 9600 baud to the laptop.

Has anybody measured it? 
26  Using Arduino / Programming Questions / Re: analogRead. When does it take the sample. on: July 10, 2011, 10:22:48 am
Don't need to worry the digitalWrite will affect the output pin before it returns, setting a pin is one cpu instruction - the fast start up of the ADC is because the way it works is to multiplex the relevant pin to the sample/hold circuit, then sample and hold it - all within the first ADC clock or two.  It takes at least 10 more clocks to do the successive approximation, one for each bit.

Thanks. My latest experiment agrees. I did another experiment without digitalWrite, and got basically the same results.  That supports digitalWrite happens very quickly, and the voltage changes by the time the digitalWrite statement is complete.

Using about 4 usec to compensate for the FASTADC analogRead delay, the samples time/voltage lines up with what I get externally on the oscope.  (I also had a few other instructions involved, and compensated 4 usec for each of those as well).

I didn't confirm, yet, for the standard analogRead times.
27  Using Arduino / Programming Questions / Re: analogRead. When does it take the sample. on: July 09, 2011, 01:37:21 pm
Thanks for the replies.

I did a little test to see if I could measure it. However, to do the test I used digitalWrite (to control an RC charge/discharge).  How much delay is there from the time digitalWrite is complete, to when the signal goes from high to low?

Not counting that delay, the values I get from when analogRead is called to when the sample is actually taken is about 15 to 17 usec. Using the fast ADC, that number drops to 2 to 3 usec.

Since 2 to 3 usec seems to good to be true, there must be a delay in the output signal change from when digitalWrite is complete to when the output voltage actually changes.

I'm not sure if I can devise a test to measure the digitalWrite delay.
28  Using Arduino / Programming Questions / analogRead. When does it take the sample. on: July 08, 2011, 08:49:21 pm
Hi all,
I understand that the analogRead takes about 100 usec.  I've been able to successfully use Jmknapp's method to get the reads much faster (closer to 20 usec). Thanks for that!

But I'm doing some fine tweaking on the program and was wondering if anybody knew off-hand whether the sample actually takes place near the beginning of the analogRead function, or closer to the end, or somewhere in the middle.  I'm recording the time of the sample and wanted to know if I should record the time just before, or just after the analogRead statement to get the time closer to the actual moment the signal was sampled.

Thanks

29  Development / Suggestions for the Arduino Project / note needed in the Reference tutorial for attachInterrupt() on: April 23, 2011, 09:54:36 pm
I was getting very strange behavior on a project using external interrupts, so I investigated it further and ended up posting this thread:
http://arduino.cc/forum/index.php/topic,59217.0.html

I think a note in the Reference section about attachInterrupts() would be helpful for users. It would make the interrupts behave as expected rather than have an interrupt occur based on something that happened before the interrupt was attached.

Near the end of that thread there is a solution given to eliminate the unexpected behavior. For now, I think a short note with the small patch code would suffice.

Others suggested that the attachInterrupt routine itself should be altered to include the fix. This seems like a good idea in the long run.

30  Using Arduino / General Electronics / Re: Voltage Regulators (LM7805) & Capacitors on: April 23, 2011, 12:34:51 pm
Actually, in many cases, something like a filter cap is just selected by trial and error, by looking at the output of the regulator during use. You make a quick guess based on experience), then correct appropriately.  It's way faster than doing a bunch of calculatuions. For some simple things, there may be no cap needed at all.

In filtering, sometimes you use a really big cap in prallel with a really small cap. The big cap gets rid of big ripple, but because it has a small amount of inductance, it can't get rid of small, high-frequency ripple, so they just try some small caps until the high-frequency is gone. It's faster than trying to calculate the inductance of the larger cap and calculating how the ripple is affected by all of the other components etc.
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