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6541  Using Arduino / General Electronics / Re: Killswitch on: May 15, 2011, 05:27:40 am
Yes that would do the trick by the look of it.

However it you're going to buy that why not just buy the correct switch?

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Rob
6542  Development / Other Hardware Development / Re: How to Make Arduino Compatible Board on: May 15, 2011, 05:23:20 am
If you stick to the supported processors you don't have to do anything software-wise. Just build it and it will work.

If you have non-standard hardware you'll have to modify some of the core files unless you are happy to place a caveat on the board, ie "A0 is used to monitor the VIN level, don't use it in your program" .

You can also add you stuff to the IDE and have it appear on the menu, but I haven't done that so I'll leave it for someone who has.
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Rob
 
6543  Using Arduino / Microcontrollers / Re: Cheap External Chip Needed on: May 15, 2011, 05:18:06 am
Quote
Using the Arduino is too slow
The Arduino is just an AVR like most others. If you can do it with a tiny13 you can certainly do it with a mega328.

Quote
I probably did something wrong though,
Yep smiley

If you use 4 pulseIn()s in a row

Code:
pulseIn(1,y);
pulseIn(2,y);
pulseIn(3,y);
pulseIn(4,y);
process_results();

you will get consecutive pulses and there will be the inter-pulse delay between each one so the time taken may be quite long. But if you don't mind missing pulses then

Code:
pulseIn(1,y);
process_results_for_1();
pulseIn(2,y);
process_results_for_2();
pulseIn(3,y);
process_results_for_3();
pulseIn(4,y);
process_results_for_4();

Should have a pretty fast response.

Quote
I found something that might work
168 pages of data sheet, what part exactly might work.
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Rob
6544  Development / Other Hardware Development / Re: ATMEL Mega1284P evaluation board avalible on: May 15, 2011, 03:47:26 am
RE the RS232 connector.

As soon as you have to solder up wires to headers and connectors it looks like a dog's breakfast. Consider the following

a) serial on a DB9 only needs 3 signals on pins 2, 3 and 5.
b) The smallest IDC connector you can get (AFIAK) is 6-way.
c) You have room for a 2x3 header (same as the ISP header).

So I would add the 2x3 header so there is a quick and neat solution to wiring up serial with IDC connectors.

THEN

If there is room. Add a 2x2 header for jumpers so the polarity can be easily swapped.

All in all this allows two Arduinos to be neatly connected with no crappy soldered wires.

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Rob
6545  Development / Other Hardware Development / Re: ATMEL Mega1284P evaluation board avalible on: May 14, 2011, 08:58:50 pm
Just looking at the extra IO header, the rows aren't .1" spaced.

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Rob
6546  Using Arduino / Programming Questions / Re: How to always ensure that sensor data is sent out in 3 characters? on: May 14, 2011, 08:56:10 pm
From memory "%03d" will pad with 0s which can be useful.

I'd also add some delimiting characters so you can sync on the data. Getting something like "<002>" makes it much easier to detect errors.

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Rob
6547  Using Arduino / LEDs and Multiplexing / Re: Possible to operate a shift register manually with switches? on: May 14, 2011, 08:52:53 pm
Quote
various things are time critical
There's nothing particularly time critical in what you are doing, the only issue is switch bounce as retrolefty said, and that only matters on the clock pin.

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Rob
6548  Using Arduino / Networking, Protocols, and Devices / Re: using SPI with Parallel LCD display on: May 14, 2011, 08:43:29 pm
The playground has a schematic for the 595 (don't put the .1uF cap on the clock line as they show) that works AFIAK. (can't find a link for it though.)

I did find this.

http://bildr.org/2011/02/74hc595/
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Rob
6549  Using Arduino / Programming Questions / Re: How to always ensure that sensor data is sent out in 3 characters? on: May 14, 2011, 08:37:16 pm
That's a pain with the Arduino Serial.print, have a look at the standard C function sprintf(), you can use that to format data into a string in memory then print the string.

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Rob
6550  Development / Other Hardware Development / Re: ATMEL Mega1284P evaluation board avalible on: May 14, 2011, 08:14:47 pm
I'd ditch the DB9 and use a header. You can get IDC DB connectors that use ribbon cable so they still look neet and can easily be mounted remotely, makes fitting the board into an enclosure easier and you can swap from male to female without desoldering a connector.

That should route easily (manually of course smiley), using the DIP doesn't really make it worse because you can run 2 lines between pins, whereas the TQFP is basically a no go zone for one layer.

Please get rid of the huge USB connector and use a mini B.
 
Add a jumper (not a solder bridge) for the auto reset so it can easily be disabled.

The headers at the end of the chip are pretty close, Ok if you use a screw driver to remove the chip from the other end but may get in the way of a chip puller.

Crystal too close to the chip, especially with a socket.

I'll shut up now, I guess it's just a quick mock up but thought I'd highlight a couple of things anyway.

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Rob


6551  Using Arduino / Networking, Protocols, and Devices / Re: Serial Frame on: May 14, 2011, 07:57:46 pm
If you have binary data that makes it harder to differentiate between data and delimiters. In my pretty picture above the value 0x40 is a sync character, of course that's a valid data character as well so if you start reading chars half way through a frame you could get all screwed up, I use some low-level timing to detect an idle line but that's all way too much for your app I would think.

So you might find it easier to stick with ASCII representations of the data and use atoi() on the receiving end to reconstruct the data.

There must be 1000s of examples in this forum by now, this problem is raised every few days. Have a search for something like "communication between two arduinos"

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Rob
 
6552  Using Arduino / Microcontrollers / Re: Bootloader for a 1284P @ 16MHz - problems :-( on: May 14, 2011, 07:47:37 pm
Thanks skyjumper, that may save people (me included) a lot of hair tearing.

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Rob
6553  Using Arduino / Networking, Protocols, and Devices / Re: Gonna bother you folks about RS485 on: May 14, 2011, 07:39:25 pm
Quote
Gotta love these little computers.
Yep, they can be very frustrating but when it works it's all worth it.

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Rob
6554  Using Arduino / Programming Questions / Re: Shift register problems on: May 14, 2011, 05:22:04 am
Shiftout runs pretty fast, what's the distance from the 328 to the SRs?

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Rob
6555  Community / Bar Sport / Re: on a pesonal note... on: May 14, 2011, 04:33:23 am
If you are like most people you'll wonder how you ever had time for work.

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Rob
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