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Wednesday, July 19, 2023

DT402D Remains in Idle After Changing Duplex Group Channel

The title of this post is a problem reported from a Digitrax user on the groups.io forum, the response from Frank Fezzie makes up the the rest. There is a lot of good information here.

A duplex equipped DT402 will respond with "Dt402D21" on screen when first started up.  The "Dt402" is the throttle type.  The second "D" indicates the presence of an RF24 duplex radio in the throttle.  The "21" indicates the version of the software installed.

A simplex equipped DT402 will respond with "Dt402R21" on screen when first started up.  The "Dt402" is the throttle type.  The "R" indicates the presence of a simplex radio in the throttle.  The "21" indicates the version of the software installed.

A non-radio equipped DT402 will respond with "Dt402 21" on screen when first started up.  The "Dt402" is the throttle type.  The " "  (space) indicates that no radio is present in the throttle.  The "21" indicates the version of the software installed.

There were two versions of the rev 21 file released.  The first was dated 5-Aug-2016  and the second and final version is dated 10-Oct-2016.  I don't remember the details now but I seem to recall there was a problem that showed up after the 5-Aug-2016 file was released.  Digitrax corrected the problem with the 10-Oct-2016 release but did not change the version number, which remained 21.  The 10-Oct-2016 version was the last one to be released.  I don't recall that there is an easy way to tell which rev 21 file is installed in a throttle.  If in doubt just reinstall the 10-Oct-2016 version which is the current file available on the web site.

Digitrax version numbers can be confusing.  They use both decimal (base 10) numbers and octal (base 8) numbers.  They sometimes mix them up.  In the rev 21 software, the 21 is an octal (base 8) number.  The octal 21 is the same as decimal 17.   In the RF24 software, the 1.1 is an octal number equal to 0.9 in decimal. DigiIPL usually shows the octal version number of software.  Digitrax would sometimes use the octal number in the file name and sometimes the would convert it to decimal (base 10) and use that in the file name.  So DigiIPL shows 1.1 for the RF24 and the file name shows r9.  While 21 appears in both DigiIPL and the file name for the version of the throttle software.  And finally they got into the bad habit of sometimes changing the software without changing the version number, which confuses everybody.

I routinely note that sometimes a DT402D throttle will not properly download the duplex name and channel info when it is plugged into the Loconet.  Give it a few seconds.  If it still hasn't got it then unplug, wait about 5 seconds, and plug in again.  I rarely see one fail to download the info on two attempts in a row.  If it does keep failing to get the info, then remove the battery to reset the throttle, put the battery back in and then plug in.  In my experience it is very, very rare to have one fail to download the duplex info after this reset. 

My theory for this is that I have noted that the throttle starts the duplex query process on the Loconet immediately when the plug starts to make contact with the wires in the jack, even while the plug is still in the process of being inserted.  And since the plug is not firmly seated yet there is the possibility of intermittent contact between the plug and jack causing Loconet messages to be scrambled.  And I think this is what causes the DT402 to fail to get the duplex information on occasion.  There is no detection and retry process for scrambled messages on the Loconet.

If you have more than one UR duplex radio on the Loconet, any combination of UR92's and UR93's or any combination of UR92's, UR93's, and LNWI's, it is critical that all devices be set to the same duplex name and channel.  JMRI's duplex tool is excellent to use for this as it checks and warns you if there are different settings on the devices on your Loconet.  <Author's Note: There are caveats with the duplex tool. See this post>The problem that gets created is that the duplex throttle receives conflicting information about duplex channel name and number which can then cause the throttle to fail to connect to the duplex radio.  This happens because all UR92's, UR93's and LNWIs on the Loconet respond to the throttle's query for duplex information.  That is why it is important that they all reply with the same info.  There is no way of knowing which response the throttle will use 
<Author's Note: research done by the author has shown that if a LNWI is present on the loconet and it's network name does not match the other devices, that is the name that will be reported to the throttle (apparently a timing matter). See this post, especially the 'conclusion' section.>.

In a properly working Loconet, and the key words are "properly working",  it does not matter which jack the throttle is plugged into, be it a UP5 or UP7, an LNRP, or directly into a UR92 or UR93.  The throttle will get the same duplex information from any Loconet jack in the system. In the old days when we were struggling with duplex problems it was thought that plugging directly into the UR92 made a difference.  This was wrong.  It turned out that it was software issues in the throttles and UR92, not which jack you plugged into.

Hope this helps clarify things a bit.

Frank Fezzie


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