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3001  Forum 2005-2010 (read only) / Troubleshooting / Re: Low power on Digital outputs on: December 05, 2010, 09:11:42 am
Did you set them to "output"? Otherwise you might be just toggling the pullups.

Udo
3002  Forum 2005-2010 (read only) / Troubleshooting / Re: Eating Batteries on: December 05, 2010, 05:38:23 am
Besides the power issues floating pins may cause any kind of extraordinary hard to detect software issues. I once had a "software issue" that took almost 1 week to detect. I did notice that the pin was behaving erratic. However whenever it was instrumented for measuring the behaviour changed. This was because of the bias caused by the measurement.
Conclusion: floating pins are a real pain. Avoid them.

Udo
3003  Forum 2005-2010 (read only) / Troubleshooting / Re: Eating Batteries on: December 04, 2010, 09:01:36 am
Yes, this enables the pullups.

Udo
3004  Forum 2005-2010 (read only) / Troubleshooting / Re: Eating Batteries on: August 24, 2009, 12:30:42 am
I do not suggest to default them to input. I suggest to default inputs to enable pullups. Sorry If this was not clear enough.

Chears, Udo
3005  Forum 2005-2010 (read only) / Troubleshooting / Re: Eating Batteries on: August 24, 2009, 12:07:24 am
I opened up a request here http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1251090339/0#0 for an improvement in the wiring libraries. In my opinion it would be very good if the libraries would default input pins to enable the pullups.

Cheers, Udo
3006  Forum 2005-2010 (read only) / Troubleshooting / Re: Eating Batteries on: August 19, 2009, 03:16:53 pm
The effect is well known in electrical engineering / digital circuit design. The well known book of Horowitz and Hill (The art of electronics) has a section called "Some comments about logic inputs" (must be 9.06 or 9.07). They highly recommend to default unused logic inputs to high and give a very good explanation why this is a good idea. And they explain why this will use up less power.

Basically the reasoning is as follows:

1) Pulling to high gives maximum possible resistance to unwanted switching because the threshold for low is usually <1V.

2) Switching consumes much more power than not switching.

So if you leave a pin floating it will cause internal switching thus consuming unnecessary power. Sometimes it will cause even worse effects.

Cheers, Udo
3007  Forum 2005-2010 (read only) / Troubleshooting / Re: Retrieing sketch from Arduino flash memory? on: December 03, 2010, 03:38:59 pm
The simplest "versioning" would be upon save to always move the old sketch <name>.pde to a file <name>.backup.timestamp.pde. A slightly more luxurious versioning would distinguish between user requested and automatic backups and cleanup older backups in a logarithmic fashion. Not a real versioning but good enough for such a sime IDE like the Arduino IDE.

Udo
3008  Forum 2005-2010 (read only) / Troubleshooting / Re: Retrieing sketch from Arduino flash memory? on: December 03, 2010, 11:38:06 am
Since code is usually intended to be not thrown away it should always be saved. Rolling back to a previous good version is a version control issue. It follows that any decent IDE should support at least rudimentary versioning.

Udo
3009  Forum 2005-2010 (read only) / Troubleshooting / Re: Retrieing sketch from Arduino flash memory? on: September 30, 2010, 03:31:09 pm
I am aware of this kind of methods. There exist several variations. That's why I said "can not be read with an ISP". You said it could be done but obviously you had the same kind of methods in mind. Seems that this was kind of misunderstanding.

To make the point clear to the others here: the "security" of the fuses depends on the value they have to protect. If they serve  to protect casual copying they are to be considered 100% secure. If they serve to protect against a determined and knowledgeable attacker forget it. No *standalone* device today (and probably none in the future) can be hardened to keep a secret against determined attacks.

I am aware that there are techniques to harden devices even against invasive attacks. However as to my knowledge this makes attacks more costly but not impossible.

Beginners might want to have a look at one of the standard books:
http://www.cl.cam.ac.uk/~rja14/book.html

Udo

3010  Forum 2005-2010 (read only) / Troubleshooting / Re: Retrieing sketch from Arduino flash memory? on: September 29, 2010, 12:24:21 pm
I do not get this comment. Of course you can read any ICs content with the proper tools. However I am unaware that you could bypass the fuses with an ISP.  Which approach are you thinking about?

Sanding of the case and reseting the fuse with an electron microscope and an ion beam will of course allow rereading with an ISP. But I would consider this cheating smiley-wink

Udo
3011  Forum 2005-2010 (read only) / Troubleshooting / Re: Retrieing sketch from Arduino flash memory? on: September 28, 2010, 04:08:02 pm
If you want to copy the executable this can be done with an ISP. This is quite simple with AVR studio. However if the producer of the board does not want you to copy the executable, then the producer can set the AVRs fuses accordingly. This will make reading it with an ISP impossible. So it depends if the producer disabled reading or not.

No matter how the fuses are it might be violating other peoples rights on their code.

Udo
3012  Forum 2005-2010 (read only) / Troubleshooting / Re: Problem with mega also question about HVP on: September 15, 2010, 03:33:21 pm
I did not look at the schematics. However pullups are usually something >1k. Hence if you power up the device and put 12V to the reset pin it would work if the 12V line can drive at least 7mA. The next issue is that this now feeds 7mA into the 5V rail. In order to compensate for this you have to ensure that current consumption on the 5V rail is at least 7mA.

You might achieve this by connecting a 680ohm resistor from 5V to ground during programming.

Udo
3013  Forum 2005-2010 (read only) / Troubleshooting / Re: Vin and arduino sleeping? on: September 07, 2010, 04:15:33 pm
And the canonical example of how to sleep and wake up for short periods seems to be this:
http://interface.khm.de/index.php/lab/experiments/sleep_watchdog_battery/

Udo
3014  Forum 2005-2010 (read only) / Troubleshooting / Re: Load capacitance on: August 10, 2010, 05:05:51 pm
Quote
My experience with fine tuning is that it is quite hard to get better than 50ppm.
I should have written

Quote
My experience with fine tuning crystals is that it is quite hard to get better than 50ppm.

but I thought this would have been clear from the context.

I have something like this http://cgi.ebay.com/EFRATOM-LPRO-101-Rubidium-10MHZ-Frequency-Standard-/300282896608 at home.  However the power consumption is somewhat increased smiley-wink

Udo
3015  Forum 2005-2010 (read only) / Troubleshooting / Re: Load capacitance on: August 09, 2010, 02:47:46 pm
My experience with fine tuning is that it is quite hard to get better than 50ppm. The issue is that the caps will often have a tolerance of 10%. And then there is temperature influence as well.

My solutions are:
1) Get somewhat close (<100ppm) and compensate the rest in software. Depending on your application this may not be an option.
2) Buy a TXCO (but I am still searching for a 16MHz version that is cheap).
3) Use an RTC for long term timing.

Udo
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