Resetting Class A4 sound decoder

[Shorty1707822079]

My Hornby Select is of the older version and cannot change CV's.

Is it possible to change CV8 to 8 using JMRI.

Best regards,

John.

[Chrissaf]

JMRI Decoder Pro which is included with JRMI can write to CV's, but JRMI cannot connect to a Select. You still need a physical interface between JRMI Decoder Pro and the locomotive decoder.

I use a SPROG II interface, which was about £45 plus the cost of a PSU when I bought mine.

[Shorty1707822079]

Hi Chris,

I have an Arduino Uno and motor shield as the interface between the loco and JMRI, and I can change CV's okay in the advanced panel, but not CV's 7 and 8 as they are read only. I read online that you can change read only CV's with the simple programmer, but alas, it will not write 8 to CV8. The loco does it's little jiggle, but I get the No ack 308 message at the bottom (see image)

[96RAF]

CV8 is classed as read only because you cannot change the assigned value in there, which defines the manufacturer's NMRA code. What is written in firmware behind this is the ability to reset a decoder by writing a specific value to this CV, which is recognised as a reset command and not an attempt to change the manufacturer's code.

You will know if the decoder has written value 8 to CV8 because the address upon a read will have gone back to 3 the factory default.

If Sprog will program on the main and you know the old address you can write to any CV including CV1, but obviously PoM does not support read-back.

[Chrissaf]

The last time I used JRMI Decoder Pro with my SPROG II was about 3 years ago. The PC on which JMRI was installed was replaced circa June 2020. I didn't re-install JRMI on the new replacement PC, so I can't fire up JRMI to test for writing to CV8.

If CV8 was 'read only' as you state, then nobody would be able to write 8 to it as a 'factory reset' therefore CV8 has to be a 'write to' CV.

PS - The only reason I bought a SPROG II for JRMI was because I was having CV read / writing issues using my Elite. These are now fully resolved, so I had no incentive need to re-install JRMI on the new PC.