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Re: [gpsd-users] Sending SiRF commands to GPS receiver

From: Alexander Carver
Subject: Re: [gpsd-users] Sending SiRF commands to GPS receiver
Date: Sun, 26 Feb 2012 12:13:23 -0800
User-agent: Mozilla/5.0 (Windows NT 5.1; rv:10.0.2) Gecko/20120216 Thunderbird/10.0.2

On 2/26/2012 11:59, Eric S. Raymond wrote:
Alexander Carver<address@hidden>:

     Send a specified control string to the GPS; gpsctl will provide
packet headers and trailers and checksum as appropriate for binary
packet types, and whatever checksum and trailer is required for text
packet types. (You must include the leading $ for NMEA packets.)
When sending to a UBX device, the first two bytes of the string
supplied will become the message class and type, and the remainder
the payload. When sending to a Navcom NCT or Trimble TSIP device,
the first byte is interpreted as the command ID and the rest as
payload. When sending to a Zodiac device, the first two bytes are
used as a message ID of type little-endian short, and the remainder
as payload in byte pairs interpreted as little-endian short. C-style
backslash escapes in the string, notably \xNN for hex, will be
interpreted; additionally, \e will be replaced with ESC. This switch
implies -f.

While it doesn't lay out the format explicitly as a full command
line example, it does document what bytes go where and what may be
needed for each one including which bytes should appear first.  It
just happens to leave out SiRF.

Yes, it does.  I'll fix that now.  How's this?

For all other supported binary GPSes (notably including SiRF) the
string is taken as the entire message payload and wrapped with
appropriate header, trailer and checksum bytes.

Thanks, that works and answers my question, too. I very rarely have to command the GPS to do anything but when I see that the SBAS was lost, kicking it with that one particular message gets it back up and running in a minute or two without having to reboot the receiver.

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