An altimeter for TomTom: an odissey

February 2007: The latest tomtom software switched from NMEA to SIRF data format, so that the altimeter does not work anymore. I'm working on this problem. please be patient

March 4, 2007: I released a first attempt to address the problem: a version of the altimeter that runs in both NMEA and SIRF modes. please download it here and consider that my unit (a Rider) can not be upgraded, so I wrote it without being able to check it. By the way, the SIRF Binary Protocol Reference Manual contains an error regarding message id 41, that slowed further my development: it says that the message has to be 91 bytes long, but if one sums the length of all listed fields, one gets a total length of 94 bytes! I had to collect several tracks and examples before working out that the "UTC day", "UTC hour" and "UTC minute" fields are 1 byte long (while they are listed as 2-bytes long on the reference manual... by the way, UTC year and UTC seconds are really 2-bytes long, while UTC month is correctly listed and implemented as 1-byte long).

April 10, 2007: The conclusion is that the autodetection of the sirf vs. nmea mode has problems. a sirf-only beta version can be downloaded here it should log a lot of stuff

April 25, 2007: Now logging works, and some sreat betatester uploaded very interesting tracks spotting a couple of bugs. The next version can be downloaded here.

April 27, 2007: a bug has been fixed. you can download the new version here.

May 9, 2007: another bug has been fixed. you can download the new version here. Please report problems along with the log files!

May 16, 2007: another bug has been fixed. you can download the new version here. Please report problems along with the log files!

June 10, 2007: after some vacation, I discovered that the traces sent by the betatesters do not adhere strictly to the standard: some bytes are missing. an attempt to circumvent the probelm can be downloaded here. Please report problems along with the log files!

June 12, 2007: another trial: altimeter-sirf-20070612.zip

June 19, 2007: another trial: altimeter-sirf-20070619.zip

June 25, 2007: it is converging: altimeter-sirf-20070625.zip

July 3, 2007: at least one of the betatesters said that the valus displayed are correct! altimeter-sirf-20070703.zip

October 3, 2007: A new version has risen, trying to unify both: altimeter-gpsfeed-20071003.zip

October 6, 2007: Some betatesters reported the previous one working, some not. A new debug version is altimeter-gpsfeed-20071006.zip