On 11/04/2015 02:02 PM, Jan Kandziora wrote:
> Am 04.11.2015 um 12:32 schrieb Martin Patzak (GMX):
>> while further investigating the problem it looks like this:
>>
>> the value of sensed.BYTE toggles between *55* (00110111) and *183*
>> (10110111) for quite a while - so its only flipping one bit.
>>
>> When I increase the toggling speed, I can provoke my *553* error from
>> *sensed.BYTE* from once a day to several times a minute.
>>
>> It looks like reading the owfs-file *sensed.BYTE* in python 2.7 is not
>> an atomic function!?!
>>
>> Any thoughts?
>>
> That doesn't mean the function is non-atomic but it means a
> copy-to-buffer operation is broken, as it doesn't add the required \0 to
> the "55" string.
>
> Which python binding to you use? Do you
>
> import ow
>
> or
>
> import ownet
>
> ?
>
> Kind regards
>
> Jan
>
Jan,
thanks for the quick reply.
I do not import ow or ownet, but read the file directly in the
file-system mounted by owfs
I started out years ago with perl and then transferred part to python. I
never got around using ow or ownet.
Can I read the \0 with a python .read() command?
The code looks like
--------- begin code -------------
def RD_IO_byte(st, path, id, error):
## this function reads sensed.BYTE and returns the bits as list of
INT starting with MSB
## if there is a problem it returns None and error[0] will be non-zero
# path - full path to owfs
# id - ID of 1-wire device
# bits - a integer list of all 8 bits from 0 to 7, the whole byte
id = os.path.join(path, id)
error[0] = -99
try:
byte = open(id +'/sensed.BYTE', 'r') # open our fuse-file
except:
print text_de.name[st], 'Could not open ', id, '/sensed.BYTE
for reading!'
return None
else:
str_byte = byte.read() # read the integer value of
BYTE as string
byte.close() # close the fuse-file
value = int(str_byte) # once in a while it crashes
here, so we need to find out why
if (value < 0) or (value > 255): print text_de.name[st], 'Got
int-value ', value, ' from string ',str_byte,' reading ', id,
'/sensed.BYTE '
bits = int2bin(int(str_byte)) # make a bit-list out of the
integer
bits = invert_byte(bits) #
error[0] = 0
#print 'error in RD_IO_byte', error[0]
return bits
----- end code ------
Martin
>
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