[PD] pduino and FSRs [and one more thing...]

Derek Holzer derek at umatic.nl
Sat Apr 12 18:02:14 CEST 2008

Some words from the grumbly old man's advice department...

In general, if you aren't 100% sure of the circuit and how it works 
(this being a very good example), you'd be best off running the Arduino 
on external power rather than power from the USB bus. Unless you want a 
non-working USB bus on your computer some day ;-)

You didn't indicate how you were powering the Arduino, so cheerfully 
disregard this email if you are already playing safe.

Have a nice day,

Derek Holzer wrote:
> This makes sense. I used some FSRs with a hacked joystick HID device and 
> got into some trouble there as well. FSRs have zero resistance when no 
> force is applied, so essentially you are short circuiting the 5v 
> directly to ground when you plug them in without any force applied. I 
> would definitely try a resistor in series with each FSR, that's how I 
> did it with the HID joystick, which also crashed (the joystick did not 
> function) when the FSR was plugged in without any resistance.
> good luck!
> d.
> marius schebella wrote:
>> hi nick,
>> did not read through the whole history of this thread but it seems the 
>> crash is related to the arduino powering down because of a short 
>> circuit. actually the usb port is the one that powers down the arduino 
>> or at least disconnect the arduino and that can cause comport to crash.
>> I think you should check your circuit again to make sure there is no 
>> short circuit. I am not sure about the phidget but what you need is a 
>> resistor connected to ground that circumvents short circuit when you are 
>> at the lowest sensor resistance. that is, when you - for example - turn 
>> a potentiometer all the way up, it connects the "in" directly to the 
>> "out", without any resistance and that causes a short circuit.
>> with the fsr it might be something similar, but it is just a guess.
>> marius.
>> nick burge wrote:
>>> OK this is getting interesting.
>>> I have got the FSRs set up again on my breadboard so I can experiment a 
>>> bit. I've tried different baud rates and get the same result...that is 
>>> to say a crash in PD.
>>> The FSRs connect to Phidget voltage dividers as recommended by the 
>>> suppliers and from the  voltage dividers we have 3 wires: analog in, 5v 
>>> and ground. Now if I swap the wires they call "analog in" with the 5v 
>>> wire on the breadboard and connect again to Pduino I can enable all the 
>>> analog inputs in the Arduino object and NO CRASH....
>>> I am no expert in electronics, but I'm sure someone can give me an 
>>> explanation as to what is going on. 
>>> Looking at the manual for the Phidget voltage dividers I see that in the 
>>> proprietry software designed for use with the phidget microprocessor 
>>> there is a setting you have to select: namely "Ratiometric" when using 
>>> these voltage dividers. Could that have anything to do with it?
>>> Nick.
>>> ------------------------------------------------------------------------
>>> *From:* Hans-Christoph Steiner [mailto:hans at eds.org]
>>> *Sent:* 12 April 2008 00:41
>>> *To:* nick burge
>>> *Cc:* Pd List
>>> *Subject:* Re: [PD] pduino and FSRs
>>> I use 6 analog inputs all of the time on Mac and Linux. I've never used 
>>> 19200 tho. Try using [comport] alone to eliminate anything in [arduino]. 
>>> Maybe there is a bug in comport on vista?
>>> .hc
>>> On Apr 11, 2008, at 3:17 PM, nick burge wrote:
>>>> Thank you Hans, am I being unrealistic in trying to have six analog 
>>>> inputs active all at once? I know you said that was a lot of data, but 
>>>> I run a fairly powerful laptop with a dual core Centrino processor, 
>>>> and Windows task manager reports only a modest demand on the cpu of 
>>>> around 30% when I have the patch running and all inputs active, so it 
>>>> seems to be an error in timing or syncronisation rather than simply 
>>>> overstressing the system that causes this....I've taken the patch 
>>>> right down to the basic arduino-test patch, but still the crashes 
>>>> occur when I activate more than 2 analog inputs. I'll experiment with 
>>>> different baud rates, go back to a usb connection rather than the xbee 
>>>> wireless system and keep trying to identify the source of the problem. 
>>>> I'll get back to you if I learn anything new. Below is the data 
>>>> produced by the event viewer in Windows in case it means anything to you.
>>>> pd.exe
>>>> 		**
>>>> 		** 	47148d16
>>>> 		** 	pd.dll
>>>> 		**
>>>> 		** 	47148d15
>>>> 		** 	c0000005
>>>> 		** 	00004e04
>>>> 		** 	17ec
>>>> 		** 	01c89bd26543018e
>>>> Nick.
>>>> ------------------------------------------------------------------------
>>>> *From:* Hans-Christoph Steiner [mailto:hans at eds.org]
>>>> *Sent:* 11 April 2008 18:30
>>>> *To:* nick burge
>>>> *Cc:* Pd List
>>>> *Subject:* Re: [PD] pduino and FSRs
>>>> Let's keep this on the list since it could be generally useful.
>>>> In order to get to the next step, you should try to isolate the 
>>>> problem, to see where the crash is actually happening. Otherwise, 
>>>> there are far too many possibilities for me to try guessing. Ideally, 
>>>> you could make a simple patch that reproduces the crash.
>>>> .hc
>>>> On Apr 11, 2008, at 3:01 AM, nick burge wrote:
>>>>> Firmata, Pduino and xbees. are all set to communicate at 19200 baud.
>>>>> Nick
>>>>> ------------------------------------------------------------------------
>>>>> *From:* Hans-Christoph Steiner [mailto:hans at eds.org]
>>>>> *Sent:* 10 April 2008 23:57
>>>>> *To:* nick burge
>>>>> *Cc:* Pd List
>>>>> *Subject:* Re: [PD] pduino and FSRs
>>>>> What baud are you running each at? IIRC, the XBee needs a strange value.
>>>>> .hc
>>>>> On Apr 10, 2008, at 5:52 PM, nick burge wrote:
>>>>>> I wish I knew. I'm loading the arduino-test patch with no other 
>>>>>> objects or abstractions so as to eliminate other suspects. Still PD 
>>>>>> crashes when I enable more than 2 analogIns.
>>>>>> Would it help to speed up or slow down the xbee connection?
>>>>>> ------------------------------------------------------------------------
>>>>>> *From:* Hans-Christoph Steiner [mailto:hans at eds.org]
>>>>>> *Sent:* 10 April 2008 23:12
>>>>>> *To:* nick burge
>>>>>> *Cc:* Pd List
>>>>>> *Subject:* Re: [PD] pduino and FSRs
>>>>>> The code and the electrics are quite separate. If the electrics work 
>>>>>> with one firmware, then they'll work with another. The question is, 
>>>>>> what is the "it" that grinds to a halt.
>>>>>> .hc
>>>>>> On Apr 10, 2008, at 4:17 PM, nick burge wrote:
>>>>>>> Yes, I've got the latest version....maybe a silly question...but 
>>>>>>> could it be that Pduino is optimised for sensors working on a 
>>>>>>> supply of 5v. because the phidget voltage dividers i've got my FSRs 
>>>>>>> attached to come with a potentiometer that alters the resistance of 
>>>>>>> the circuit...with pduino i can only activate 2 at a time before it 
>>>>>>> all grinds to a halt...on arduino2PD i can activate all six without 
>>>>>>> any problem. Strange.
>>>>>>> Nick.
>>>>>>> ------------------------------------------------------------------------
>>>>>>> *From:* Hans-Christoph Steiner [mailto:hans at eds.org]
>>>>>>> *Sent:* 10 April 2008 21:51
>>>>>>> *To:* nick burge
>>>>>>> *Cc:* Pd List
>>>>>>> *Subject:* Re: [PD] pduino and FSRs
>>>>>>> I've never run on Vista before, so I can't say much about that. I 
>>>>>>> have run on Debian, Ubuntu, and Mac OS X. It shouldn't matter what 
>>>>>>> is generating the data on the arduino, the messages coming to Pd 
>>>>>>> via the serial port should be all the same.
>>>>>>> Are you using the latest version:
>>>>>>> http://at.or.at/hans/pd/Pduino-0.3.1.zip
>>>>>>> .hc
>>>>>>> On Apr 10, 2008, at 12:57 PM, nick burge wrote:
>>>>>>>> Hello Hans-Christoph, I am using PD 0.39.3 extended. on a windows 
>>>>>>>> vista system. Its PD that crashes, or "stops working" as Vista so 
>>>>>>>> nicely puts it, when I connect the FSRs.
>>>>>>>> I have arduino connecting via wireless xbees at 19200 baud.
>>>>>>>> I also use an infra red distance sensor that gives no problem.
>>>>>>>> I've been routing the data from the FSRs through the autoscale object.
>>>>>>>> Maybe I should find a way to reduce the amount of data being 
>>>>>>>> sampled...every 40ms for example? How would I do that?
>>>>>>>> Nick.
>>>>>>>> ------------------------------------------------------------------------
>>>>>>>> *From:* Hans-Christoph Steiner [mailto:hans at eds.org]
>>>>>>>> *Sent:* 10 April 2008 17:25
>>>>>>>> *To:* nick burge
>>>>>>>> *Cc:* Pd List
>>>>>>>> *Subject:* Re: [PD] pduino and FSRs
>>>>>>>> Which program crashes? Which version are you using? You will get a 
>>>>>>>> lot of data, from 6 sensors, Pduino/Firmata will read them all 
>>>>>>>> every 20ms. I have never seen a crash using [arduino], except when 
>>>>>>>> I unplug the arduino when Pd is connected to it, so I suspect the 
>>>>>>>> problem lies elsewhere.
>>>>>>>> .hc
>>>>>>>> On Apr 10, 2008, at 11:16 AM, nick burge wrote:
>>>>>>>>> I have a little problem using Pduino and some force sensing 
>>>>>>>>> resistors that I am using in conjunction with phidget voltage 
>>>>>>>>> dividers....they seem to crash the program as soon as I activate 
>>>>>>>>> more than 1 at a time.....
>>>>>>>>> Should I be applying some sort of filter to the data stream?
>>>>>>>>> Arduino2PD seems more robust, allowing me to activate all 6 
>>>>>>>>> analog inputs at once.
>>>>>>>>> Nick Burge.
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derek holzer ::: http://www.umatic.nl ::: http://blog.myspace.com/macumbista
---Oblique Strategy # 20:
"Be extravagant"

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