Sorry, I think I tried to say too many things at once.
The stability problems always existed. It got better after changing
to cat5 cables with a clean bus topology, but never went away.
I will try upgrading to the latest version, if that could really
change things. After all the problems I have had with 1wire (mostly
due to bad implementation of cabling) I always think about the
hardware beeing the problem....
Michael
On 09.01.2007, at 14:56, Paul Alfille wrote:
On 1/9/07, Michael Weber <[EMAIL PROTECTED]> wrote:
I have some problems running a PID-Temperature Controller. It works
fine most of the time, but tends to crash with varying frequency
(months to hours).
So yesterday, I changed from the old python module to the ownet
interface (but still use the old v2.4.1 owserver binary) and
encountered the following error (obviously during the read of a
temperature sensor)
ValueError: negative buffersize in recv
The program is very simple: It reads the temperature every minute,
calculates the updated P, and I gains and the correction terms from
those. If the term is 0 or 1, the heater is turned off or on, if it
is inbetween, the heater is put into PWM mode. Most of the writing
I encapsulated in "try." already, but since yesterday I know that
the problem seems to be (also?)the temperature reading.
Any suggestions? Since the first implementation of this regulator,
I rewired the bus using CAT5 cables, and I removed all the "star"-
parts from the topology. Cable length is less than 50m, the
connection is done via a MOXA port server, a serial-to-1wire
converter including a filter.
Well, you've changed only one thing, and that changed from working
to non-working? My thought is that either the 2.4.1 owserver tcp
protocol was slightly different, or that there is an error in ownet.py
If it is easy to test a current version of owserver, that would
simplify the analysis. In 2.4.1 there were no owserver protocol
clients besides the owserver library so the protocol wasn't as well
tested for bad field values.
A 1-wire PWM module? Very interesting.
Electrical problems on the 1-wire bus should not give protocol
errors. owserver should filter them out.
The circuits we use are available at
http://www.aip.de/People/wbittner/1wire/index.html
Sorry, only in German:
"Spannungseinspeisung am Master Kabel auch hier!" is the serial-
ow converter
"Temperatursensor für Daisy Chain Verkabelung mit RJ12 Anschluß für
Sensoren" is the Temperature sensor
"PWM Modul für Heizungsregelung" is the PWM-heater module
Dr. Michael Weber
Astrophysikalisches Institut Potsdam
An der Sternwarte 16
D-14482 Potsdam
Tel: 0331 7499 351
Fax: 0331 7499 200
email: [EMAIL PROTECTED]
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