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1891  Using Arduino / Networking, Protocols, and Devices / Re: Finally taking a look at the XBee library on: October 31, 2012, 08:18:50 am
Jack, I must be misunderstanding something because in AT mode, everything going in the serial port goes out the transmitter (except commands), and if you're using API mode, you can't see it unless you piggyback off the serial pins for something to monitor.

Correct, it can't be seen because it doesn't go out over the air, and that is exactly what I do, piggyback on the serial pins. That is a node-at-a-time scenario of course. I do remember the approach of using broadcast for everything and then being able to monitor all network traffic from a single XBee. Cool idea, at least until the network chokes from lack of bandwidth.

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And regarding API mode 1, we've had this discussion twice now.  The digi document is somewhat vague and people constantly misread it.  I've even shown you code that works regardless of the data sent in API mode 1.   Remember this thread a while back where I showed you working code under API mode 1?  http://arduino.cc/forum/index.php/topic,76591.0.html

Wow, that was a year ago! Now I do suffer from a condition called CRS, which is a side-effect of too many birthdays, but I did review that thread and the product manual again, and I'm evidently still misreading it. Please try me again because I really would like to understand your point.

I'll try again too, here is the way I see it:

The illustration from that thread seems abundantly clear to me: If AP=2, then everything after the 0x7E start delimiter, including the length bytes and checksum, needs to be escaped. EDIT: And, if AP=1, then certain characters cannot be sent because they interfere with frame sequencing. These are 0x7E (frame delim), 0x7D (escape), 0x11 (XON), 0x13 (XOFF).

The example you showed was just that, an example, a special case that just happens to work. But here's what I don't understand: What if the packet length had been 0x13, a value that needs to be escaped? What if unicast mode was being used and the destination node had 0x7E as part of its 64-bit address, as in the case of the OP in the other thread? I do not see a general case where AP=1 can always be counted upon to work (i.e. have no bytes that need escaping).
1892  Using Arduino / Networking, Protocols, and Devices / Re: Finally taking a look at the XBee library on: October 30, 2012, 08:48:13 pm
The additional traffic (debug messages) don't make it onto the network, the XBee ignores them. But on a very active node it can be hard to pick things out. My data rates are quite low, but even so, a terminal program with capture-to-disk capability is often very helpful.

Regarding API mode, when using it, I only use AP=2. I have yet to figure out why a person would use AP=1, or indeed why it even exists. Rapp specifies that AP=2 should be used with his library anyway.
1893  Using Arduino / Networking, Protocols, and Devices / Re: Finally taking a look at the XBee library on: October 30, 2012, 06:09:39 pm
I will have a look as well, but just off the top, I don't get it. I've used Andrew Rapp's library with S2 XBees in API mode for some time now, exclusively on ATmega328Ps, and it is really useful. For debugging purposes, I just write debug messages to Serial exactly as I might without an XBee in the picture. As long as the debug messages don't include the 0x7E start delimiter (easy enough to avoid, yes?), the XBee ignores them. Sure, on the serial monitor I see the XBee traffic as interspersed gobbledegook, but it is debugging after all.
1894  Using Arduino / Microcontrollers / Re: ATTiny85 run at 1Mhz When I Program "delay(1000)" does not give 1 second? on: October 30, 2012, 10:23:36 am
So I can run it at 16mHz with no external crystal...? Cool!

Yes, I do believe that is true!

Looks like these chips still have a few surprises left... It seems weird that I never saw 16mHz mentioned anywhere and there's no option for it in any of the Tiny85 IDE add-ins I've seen.

Arduino-Tiny comes with a boards.txt entry to run at 16MHz using the PLL.
1895  Using Arduino / Microcontrollers / Re: ATTiny85 run at 1Mhz When I Program "delay(1000)" does not give 1 second? on: October 30, 2012, 09:17:16 am
16MHz divided by 8 = 2MHz
Yeah but the PLL when used as system clock source is nominally a 64MHz clock, so divided by 8 gives 8MHz.

While I haven't actually actually tried this clock option myself, the way I read it is that setting CKSEL[3:0] configures a 16MHz system clock by dividing the 64MHz PLL by 4. Now on top of that, lfuse=0x61 sets the CKDIV8 bit, which further causes the clock prescaler to divide by a factor of 8 on top of that.
1896  Using Arduino / Networking, Protocols, and Devices / Re: Xbee digital Input/Output voltage on: October 30, 2012, 07:34:54 am
I think some people supply xbee with 3.3V and interface RX/TX pin with a 5V microcontoller without any interface.

They do, but they shouldn't.

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Is this safe?

Not according to the manufacturer:
http://www.digi.com/support/kbase/kbaseresultdetl?id=2160
1897  Community / Bar Sport / Re: Good luck all of you guys on the East Coast :-( on: October 30, 2012, 07:10:36 am

Wowsa. That's quite a picture. The way those trucks are laying is amazingly consistent.
1898  Using Arduino / Microcontrollers / Re: ATTiny85 run at 1Mhz When I Program "delay(1000)" does not give 1 second? on: October 30, 2012, 06:59:44 am
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1. Change the fuse bits so the ATtiny85 uses 16MHz PLL and divide clock by 8 by running the 
following command: 
avrdude ‐p ATtiny85 ‐c usbtiny ‐U lfuse:w:0x61:m ‐

So it was in fact still running at 16Mhz then I think which explains everything if it was ?

16MHz divided by 8 = 2MHz
1899  Community / Bar Sport / Re: Good luck all of you guys on the East Coast :-( on: October 29, 2012, 04:53:47 pm
We're quite a ways inland, on the rare occasions that we do get "remnants" of a hurricane, it's usually not distinguishable from just the average rainy spell. This one is sounding like it'll be above average, especially where wind is concerned, but I'm not overly worried. Folks out East will bear the brunt of it. Crossroads will probably see much more than we will, and I think he's a bit North of the worst part.
1900  Community / Bar Sport / Re: Good luck all of you guys on the East Coast :-( on: October 29, 2012, 07:27:38 am
Southeast Michigan here. Not expecting anything too extreme, but I saw one prediction of waves up to 22 feet on Lake Michigan around Chicago. That is pretty unusual. Planning to head out shortly and stock up on petrol for the generator just in case the remnants of Sandy cause any outage here.
1901  Using Arduino / General Electronics / Re: Switching to lead-free soldering on: October 29, 2012, 07:23:29 am
My intent is to avoid it if at all possible, but maybe that is not a possibility in Belgium. I've always used only Kester solder, so if I had no other choice, I would look at their lead-free solder first.
1902  Using Arduino / Project Guidance / Re: Water level probes with minimal componant count? on: October 28, 2012, 02:13:47 pm
FWIW, here is the circuit I use to monitor my sump. Like I said earlier, the probes are dry under normal circumstances, so not a big worry about electrolysis anyway. I turn the sense voltage on for 10ms and sample once/second, so a 1% duty cycle. I figure the input impedance must be on the order of 500K, so around 7µA of current through the probes with a 3.3V supply. Not sure how much electrolysis that might cause, but I figured it was negligible in my scenario. It's quite sensitive as well.

Interestingly, I used an LM1830 fluid level detector many, many years ago that was designed to output an AC voltage to prevent electrolysis. It's not made any more, when I went looking for a replacement I came up empty. Wonder why that is.
1903  Using Arduino / Motors, Mechanics, and Power / Re: Servers,Server Rack, Temperature on: October 27, 2012, 10:07:27 pm
Thanks for the information sir. This helps me a lot.
In our school the server rack are close  but not all. Do you have any idea about the temperature range?

Not sure whether you mean close or closed, but I'd be very surprised that even if there is a solid glass front door on the cabinet, the back will be open or nearly so. Often the cooling air is brought in from below with a false-floor arrangement. Proper racks will be designed to facilitate proper airflow even when they are right next to each other. There may be specs on aisle space.

I do not know any temperature ranges, I will again have to direct you to the equipment manufacturer. There may be some standard, or if not a formal standard, then a typical industry rule of thumb. I've spent a fair amount of time in data centers, usually knew the environmental guys but did not get into that part myself. It can get pretty involved, measuring, adjusting temperatures and airflows. I wouldn't be surprised if the racks have specifications regarding airflow (CFM) and maximum heat (BTUs) that can be exhausted. Equipment specs should also include BTUs.
1904  Using Arduino / Motors, Mechanics, and Power / Re: Servers,Server Rack, Temperature on: October 27, 2012, 09:41:32 pm
I would consult the specifications for the particular server(s) being used. But I doubt they will differentiate between "server room temperature" and "server rack temperature". Most racks are very open, the idea being that the air available to the racked equipment is essentially the same as the room air.

Equipment manufacturers will usually just specify a single ambient temperature, which is assumed to be the temperature of the air being drawn into the equipment.

Not sure what you are trying to accomplish, but most modern equipment made in the last decade or two has built-in temperature sensors which are read by various management software that can automatically raise an alert if something is running hot.
1905  Using Arduino / Microcontrollers / Re: ATTiny85 run at 1Mhz When I Program "delay(1000)" does not give 1 second? on: October 27, 2012, 06:08:18 pm
Thanks both Fuses must have been wrong Fungus was right all along
Bootloaded 8Mhz to chip then loaded program and delay is now right .

Good deal!

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I just wondered Jack is there any power usage difference between running at 8 and 1 Mhz ?

Yes, generally, the slower the clock, the lower the power consumption. See Figs 22-2 through 22-4 in the datasheet. If my well-calibrated eyeball serves, at 3V, 0.6mA at 1MHz vs. 2.8mA at 8MHz.
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