On Thu, 08 May 2014 08:23:01 -0700, Richard wrote:

What is your take on a 4800 baud rate system that also transmits
PowerFlarm and Vario sentences two ways.

I don't have enough information to make any estimate. To do that you need
to know:

- baud rate and character format

- format of the various messages exchanged with the FLARM and vario

- the frequency and order in which the messages are exchanged.

and I don't have any of this stuff.

I am able estimate the spare capacity in a GPS receiver's output stream
because I found the NMEA sentence formats and character format (8N1) on
the 'net [1] and spent some time with a Garmin GPS2+ and a GPS35 hooked
up to the serial port on a PC, watching the data stream and working out
how it changes as the GPS settings are changed, i.e. no active route,
active routes with different numbers of waypoints.

[1] http://aprs.gids.nl/nmea/ gives some NMEA sentence formats: enough
for our purposes and the NMEA 0183 specification gives baud rate and
character encoding. However, this stuff is quite hard to find because it
seems that the standards that define NMEA sentence formats and ordering
are not exactly an open source document. The full spec will set you back
around $2800.

BTW, it seems that 38400 baud is also a standard NMEA transmission rate.
It is used for AIS (Automatic Identification System), an automatic
tracking system used on ships and by vessel traffic services (VTS) for
identifying and locating vessels by electronically exchanging data with
other nearby ships, AIS base stations, and satellites.


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martin@ | Martin Gregorie
gregorie. | Essex, UK
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