Hi Paul,

any feedback for me regarding this patch?

Best regards,
Clemens Egger

> -----Original Message-----
> From: Egger Clemens
> Sent: Thursday, 02 May, 2013 2:44 PM
> To: [email protected]
> Subject: DS1921 Thermochron Patch - Mission Start Delay, Stop Mission
> 
> Hi Paul,
> 
> while working with the DS1921 Thermochron iButton I came across a few
> problems. See attached patch file for fixes.
> 
> - mission/clear not working: I made visible mission/clear (for reasons
> explained below), however the assigned read/write functions
> FS_r_controlbit, FS_w_controlbit had no effect; writing 1 to mission/clear did
> not clear the iButton.  I wrote a separate function FS_clrmem, which basically
> calls the already existing function OW_clearmemory(). This way it was
> possible to clear the mission of the iButton. Since the mission/clear never
> read anything else than 0, I assigned NO_READ_FUNCTION.
> ("The EMCLR bit returns to 0 as the next memory function command is
> executed", [#ds page 14])
> 
> - It is not possible to use the Mission Start Delay: FS_w_samplerate uses
> OW_startmission to set the Sample Rate. However the function
> OW_startmission performs a clear memory by calling OW_clearmemory,
> which also clears a previously set Mission Start Delay. Afterwards the Sample
> Rate is written and therefore the mission starts. This way there is no
> possibility to use the Mission Start Delay.
> I removed OW_clearmemory from OW_startmission and inserted a separate
> OW_clearmemory for the function FS_easystart.
> This way mission/clear is needed to do the missioning.
> 
> - The function OW_stopmission does not work: As intended in the code a
> mission can be stopped by writing 0 to either mission/frequency or
> mission/running. However doing so, the sampling is not stopped. The
> function OW_stopmission just performs a read, there's also a comment
> saying "dummy".
> The datasheet states "A mission ends with the first write attempt (Copy
> Scratchpad command) to any register in the address range of 200h to 213h.
> Alternatively, a mission can be ended by directly writing to the Status 
> register
> and setting the MIP bit to 0. The MIP bit cannot be set to 1 by writing to the
> Status register.", [#ds page 15]
> I implemented the way to set the MIP in the status register to 0.
> 
> - Typos and probably copy-and-paste leftovers in man pages: DS1921 and
> DS2438.
> 
> I'm aware that this patch breaks the feature to start a mission by writing 1 
> to
> mission/running - in that case a previously set frequency was re-used for a
> new mission after performing a clear-memory. Since this feature seems not
> to be documented in the man page I was not sure how to proceed and
> wanted to discuss this point with you. I'm happy to fix the code in either 
> way:
> to restore the feature or to remove its remaining residuals. I'm also willing 
> to
> add additional documentation to the DS1921 man page about the missioning
> and mission/clear.
> 
> best regards
> Clemens Egger
> 
> 
> Reference:
> #ds: DS1921G datasheet
> (http://datasheets.maximintegrated.com/en/ds/DS1921G.pdf)
> 
> 
> --
> Clemens Egger
> Center for Biomedicine
> 
> EURAC research
> Galvanistr. 31, I-39100 Bozen
> t +39 0471 055 524
> f +39 0471 055 599
> [email protected]
> www.eurac.edu


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