On Thu, Nov 06, 2014 at 12:41:20PM +0100, Tam=E1s Fekete wrote:
> Hi everyone!
> I am not sure if this problem is related to this topic. But I don't
> know where else it would fit.
>  I am using a dspic33fj128mc802 with mplab xc16 compiler. I have to
> read data from an ADC at about 1ms intervals. The data that I get is
> a floating point number. I convert this number into a string using
> the function sprintf. Send out the string. At the PC side I receive
> and save the data with putty.exe. Then save the session in a .dat
> file. I can use this .dat file with matlab to plot the results.
>=20
> The problem is that sprintf really slows down the process. I should
> be taking samples at about 1ms intervals and because of the sprintf
> function this is between 5-7 mseconds. I checked this with an
> oscilloscope and without the sprintf function I can get down to even
> less than 1ms intervals easily.
>=20
> If anybody could suggest a faster way to make a string out of a
> floating point number or another way to send and receive the data I
> would be very thankful.

Yes, I've had sprintf take all the time it likes.

What I would do is read the data from ADC registers and either
transmit it as is, or encode it as hexadecimal.  Then do the
conversion on the PC side.

But I don't know that chip, so I can't be specific.

Also, I don't know the compiler or library you mention, so I don't
know what other functions might be available.  I would check for ecvt
or some equivalent, and compare conversion time against sprintf.

--=20
James Cameron
http://quozl.linux.org.au/
--=20
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