[aprssig] Is floating point telemetry allowed in APRS?

Charles Bland root at blandranch.net
Thu Mar 28 15:21:01 CDT 2013


It makes no sense to me to limit yourself to x.x, when you can use mic-e
telemetry that gives you larger range of values and the equation values
that are part of the spec.

Not arguing with Bob...... just sayin' the spec is actually pretty decent
for telemetry. Ya, it can be better, but within the spec there is a fair
amount of capability.

Chuck

On Thu, Mar 28, 2013 at 8:58 AM, Robert Bruninga <bruninga at usna.edu> wrote:

> Actually, the original APRSdos can take decimals, but again, the limit is
> 3 FIXED bytes.  So you can have 0.1 up to 9.9, but beyond 10, you cannot
> use a decimal because it would make the field 4 bytes wide and violate the
> spec.  Same goes for SPEED field.
>
> Im not sure if the spec is that clear or not.  Don't have time to dig.
> But the 3 bytes *is* the spec requirement, any positive number you can
> stuff into 3 bytes should be OK.   I even allow up to 999 which is getting
> close to 10 bit accuracy..
>
> Bob, WB4APR
>
> -----Original Message-----
> From: aprssig-bounces at tapr.org [mailto:aprssig-bounces at tapr.org] On Behalf
> Of Matti Aarnio
> Sent: Thursday, March 28, 2013 11:10 AM
> To: TAPR APRS Mailing List
> Subject: Re: [aprssig] Is floating point telemetry allowed in APRS?
>
> On Wed, Mar 27, 2013 at 04:09:12PM -0400, Steve Dimse wrote:
> > The spec is not fluid that way. If it says telemetry should look like
> ...
>
> The spec isn't fluid in many ways.  If you start to take a strict view
> of what is carried in APRS-IS is only what aprs-1.01.pdf says, then most
> of BoB's "errata" and "update" documents become irrelevant too -- and
> frankly the whole APRS becomes an obsolete dinosaur starting with
> prohibiting use of any characters outside ASCII.
> (Tell that to Japanese, Greek, European in general...)
>
> Telemetry is just one small example of things codifying what one
> particular
> ancient microprocessor was capable of doing.  Strictly speaking it
> prohibits
> reporting 10 or 12 or 16 bit ADC values, which has never stopped anybody
> from
> doing it anyway.
>
> If receiver's display routines are converting integers to rational numbers
> for displaying, or plotting, what would prevent from from parsing a
> rational
> number to begin with?
>
> Very long ago I was doing something where we considered for a moment about
> using APRS for telemetry.  We needed something like 20 ADC data channels,
> 50 booleans...
>
> 73 de Matti, OH2MQK
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