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76  Forum 2005-2010 (read only) / Interfacing / Re: serial port unreliable on: May 21, 2008, 05:26:08 pm
i've hooked up a laptop near the Arduino to see if the problems are cable related, but...

The 150 foot USB cable has hardware repeaters built into it and is exactly what it is -- a prebuilt USB cable, but it is cheap and Chinese, so perhaps it is the problem.  But why should the serial port require an Arduino reboot when there is a problem?  Shouldn't it be able to handle issues more gracefully?  I don't mind occasional occurrences of bad data -- I just can't handle the lockups.
77  Forum 2005-2010 (read only) / Interfacing / serial port unreliable on: May 21, 2008, 01:04:39 pm
I've had an Arduino-based circuit controlling a solar hydronic installation for one and a half years now (it's  an Arduino NG with an ATMEGA168 chip). This system is completely reliable, making sure water gets heated when the sun is out and turning off everything when the water coming from the panel is too cool to be useful.  I can monitor this Arduino remotely using a 150 foot USB cable (they used to be available for cheap from until that company started charging a minimum of $35 for shipping and handling).  My question concerns the reliability of the Arduino serial port.  It seems to work for awhile (a few hours) and then it inevitably locks up, requiring the board to be rebooted in order to resume communications. I've seen this behavior with several NG boards, connected to both Windows and Debian machines.  At least on the Windows machine, I'm running the latest version of the FTDI USB Drivers. Does anyone know how to improve the reliability of the serial port?
78  Forum 2005-2010 (read only) / Interfacing / Re: Proto Shield v.1a questions on: November 19, 2006, 09:14:14 am
i've only used the avr-pg1 with the Olimex avr-p28 board, which is a great cheap $16 substitute for an arduino, though it trades USB support for open breadboard space. you can examine the schematic of that board and compare it to the arduino to deduce the mapping.


79  Forum 2005-2010 (read only) / Interfacing / Re: What USB does Arduino Use?? (USB1.1 or USB2.0) on: October 20, 2006, 11:01:49 am
50 meters is a long distance.  If you want to go with a USB-only solution, you can try using cheap Chinese usb 1.1 extension cables:
they're 30 meters, only $19 each, and if you put a hub halfway between them you could probably keep them going.

I'm using one of these lengths to successfully control an Arduino solar heat sufficiency controller down in the house's boiler room.
80  Forum 2005-2010 (read only) / Interfacing / Arduino Atmega8 vs Atmega168 pin mapping on: October 29, 2006, 02:39:44 pm
Does anyone know to what extent the Atmega168 and Atmega8 have different PDIP pinouts?  I'm noticing a strange behavior with my Arduino board when I use Atmega168 vs Atmega8.  When I set Arduino's Digital Pin 13 to input, I can use it that way successfully if the processor is an Atmega8.  But if it's an Atmega168 it always reads as 0.  Pin 12 works fine with both processors.  Now it's possible I have a defective Atmega168 - but I've seen this behavior with two Atmega168s.  

I just looked at the Arduino USB schematic
and see that there is a 1K resistor only on Digital Pin 13 - perhaps the Atmega168 is more sensitive to its effects than the Atmega8.
81  Forum 2005-2010 (read only) / Interfacing / Re: 1-wire on: October 23, 2006, 01:04:28 pm
unless, of course, you're making a generic USB-to-one-wire interface with an Arduino board.  that would be a useful gizmo.  i imagine the protocol is some sort of serial thing with device addressing, sort of like usb but half-duplex.
82  Forum 2005-2010 (read only) / Interfacing / Re: 1-wire on: October 23, 2006, 01:01:27 pm
i'd save those for a non-Arduino project, since the A/D would be wasted on it.  it's too easy to just use a cheap thermistor.  
83  Forum 2005-2010 (read only) / Interfacing / Re: 1-wire on: October 22, 2006, 12:52:17 pm
hmm, one wire?  they'd have to have two to actually do anything, and then they'd be thermistors, in which case they'd be variable resistors.

1. measure their resistance at room temperature.
2.  find a fixed resistor with that measured value (or something near it)

3. connect one between VCC and an analog-in on the Arduino
4.  connect the fixed resistor between analog-in and ground.

This makes a voltage divider based on the value of your thermistor, and the numbers from reading the analog in will have a linear relationship to temperature.  you just have to find out what that relationship is and write a function to translate.  I keep everything integer in my thermistor readings to keep things simple.  Thus 989 means 98.9 degrees Fahrenheit, etc.
84  Forum 2005-2010 (read only) / Interfacing / Re: bootloader and the parallel port programmer on: October 21, 2006, 10:41:15 am
I don't know what was going on with my parallel programmer - I resoldered it and it seems to be perfect now. Shielding and such were unnecessary. I guess I'd done a crappy solder job before.  All the those resistors are buried in epoxy now and it is perfectly reliable.
85  Forum 2005-2010 (read only) / Interfacing / bootloader and the parallel port programmer on: October 19, 2006, 09:07:47 pm
I built one of those parallel port programmers following the instructions on
and, not looking carefully, I used 470K and 220K ohm resistors instead of the ones specified.  It didn't work, of course, and then I realized I only had 560 ohm resistors, not the 470 specified.  Interestingly, this made the programmer work, but unreliably. I'd get various numbers of flash errors - sometimes as few as eight and sometimes as many as 20 depending on how close I was to 470.  Eventually I found some 470s and it works most of the time but is still unreliable. I still get flash errors - always at least two.  If I try to flash several times and end on low number of errors the bootloader usually works and I can use it in the Arduino world.

Does anyone have any ideas for how to lower the error rate?  Should I be shielding the cables or something? Should I be using ferric cores?   I have no idea what speed the data is traveling at inside the programmer, though it must be some sort of serial system.
86  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Arduino board & stability on: January 16, 2007, 09:09:02 pm
I'm running the Arduino board continuously to control a hot water solar panel pump based on the data from several temperature sensors.  The board itself is very reliable, but occasionally the serial port hangs and needs to be disconnected and then reconnected - though this might not be the Arduino's fault.  I have, however, seen this behavior when using it with both Linux and Windows boxes.  But I'm connecting through a cheap Chinese 150 foot USB cable that I know to be unreliable in electrically noisy environments.
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