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Posted by Alexander Klink on August 11, 2009, 6:03 pm


Hi,

I've recently stumbled over this site
http://artico.lma.fi.upm.es/numerico/miembros/antonio/async/
which describes a way to get "raw" data from Garmin devices
in order to postprocess them with DGPS data from GPS devices
at a fixed location (for example the ones at the EUREF network
here in Europe).

I've tried it with my Garmin eTrex Legend HCX, but unfortunately
this is what happens:

> /usr/local/src/gar2rnx$ ./async_1_23 -o bindata.g12 -rinex -p ttyUSB0
> -----------------------------------------------------------------
> * Async Software to log raw GPS data from some Garmin handhelds *
> * Version 1.21. Copyright 2000,2001 Antonio Tabernero Galan *
> -----------------------------------------------------------------
> Serial port: /dev/ttyUSB0. Command: Log async events for Rinex.
> Log-time 30 sec. Output binary file bindata.g12
> -----------------------------------------------------------------
> Position : Lat 49.XXXX Long 8.XXXX
> Civil Date: 09/08/2009 13:29:51
> GPS Time : GPS Week 1544 ToW 48604 sec. Garmin Weekdays 7161
> Product ID: 694 ("eTrex Legend HCx Software Version 3.00"). Firmware 3.00
> -----------------------------------------------------------------
> Waiting for a 3D fix (10 secs at most)
> -----------------------------------------------------------------
> Serial Comm Error 2560 -> 0x00000a00: TIMEOUT waiting for a PACKET
> GPS doesn't answer in /dev/ttyUSB0: Is it on and in GRMN/GRMN mode?

Here is the trace of that:

Clearing line
OUT: 10 1C 02 00 00 E2 10 03
Purging comm port : 10 06 02 1c 00 dc 10 03 :: 8 chars purged
OUT: 10 0A 02 02 00 F2 10 03
CHKSUM OK
IN : 06 02 0A 00 EE
Packet ID 0A ACK by GPS
IN : 11 10 7B 85 D2 3F 92 DB EB 3F D1 93 43 C4 57 50 C3 3F 23
CHKSUM OK
Received correct packet ID 11 -> ACK sent back OUT: 10 06 02 11 00 E7 10 03
OUT: 10 0A 02 05 00 EF 10 03
CHKSUM OK
IN : 06 02 0A 00 EE
Packet ID 0A ACK by GPS
IN : 0E 08 08 0B D9 07 12 00 2F 34 82
CHKSUM OK
Received correct packet ID 0E -> ACK sent back OUT: 10 06 02 0E 00 EA 10 03
OUT: 10 FE 00 02 10 03
CHKSUM OK
IN : 06 02 FE 00 FA
Packet ID FE ACK by GPS
IN : FF 75 B6 02 2C 01 65 54 72 65 78 20 4C 65 67 65 6E 64 20 48 43 78 20 53 6F
66 74 77 61 72 65 20 56 65 72 73 69 6F 6E 20 33 2E 30 30 00 56 45 52 42 4D 41 50
20 52 65 63 20 52 6F 75 74 61 62 6C 65 20 48 77 79 20 42 61 73 65 6D 61 70 2C 20
41 54 4C 20 76 32 20 32 2E 30 30 00 56 45 52 53 4D 41 50 20 6D 61 73 74 65 72 5F
65 64 69 74 69 6F 6E 20 30 2E 30 30 00 1D
CHKSUM OK
Received correct packet ID FF -> ACK sent back OUT: 10 06 02 FF 00 F9 10 03
OUT: 10 0A 02 02 00 F2 10 03
CHKSUM OK
IN : 06 02 0A 00 EE
Packet ID 0A ACK by GPS
IN : 11 10 7B 85 D2 3F 92 DB EB 3F D1 93 43 C4 57 50 C3 3F 23
CHKSUM OK
Received correct packet ID 11 -> ACK sent back OUT: 10 06 02 11 00 E7 10 03
OUT: 10 0A 02 05 00 EF 10 03
CHKSUM OK
IN : 06 02 0A 00 EE
Packet ID 0A ACK by GPS
IN : 0E 08 08 0B D9 07 12 00 2F 34 82
CHKSUM OK
Received correct packet ID 0E -> ACK sent back OUT: 10 06 02 0E 00 EA 10 03
OUT: 10 1C 02 FF FF E4 10 03
CHKSUM OK
IN : 06 02 1C 00 DC
Packet ID 1C ACK by GPS
IN : 27 02 20 00 B7
CHKSUM OK
Error# 9 -> Error Code 512
Error# 11 -> Error Code 2560
OUT: 10 1C 02 20 00 C2 10 03
CHKSUM OK
IN : 06 02 1C 00 DC
Packet ID 1C ACK by GPS
Error# 9 -> Error Code 2560
Error# 11 -> Error Code 2560

From the source, it looks like enabling async leads to the error code.
Does anybody have an idea if the protocol changed? All protocol
descriptions I could find seem pretty similar. And part of the protocol
(reading the device information, date, position, ...) seems to still
work.

Any insight on this is highly appreciated ...

Thanks in advance,
Cheers,
Alex

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