Sansa E280 & USB Keypad mode

[meddyman]

I have a Sansa E280 V.1 & running Sansa Ver. 1.02.24a firmware all is good. I just learned of Rockbox and the fact it can read large capacity memory cards in the E280. I'm in! Downloaded and installed RB Ver 3.15 All appears well...until I go out to the car and plug it into the USB port my Pioneer in dash DVD player (Model AVH-190DVD). Previously,  running Sansa frmwr I was able to use the Pioneer (connected with the USB cable) to navigate the Sansa and select the artist or tune I wanted and away we go. Now I plug it in and the Sansa says "USB Keypad Mode:Mouse" (I can change Mouse to Browser, presentation, or Multimedia)
And the Pioneer say "Unrecognized USB Device". Yes, I can still hold the << button to get to the Sansa frmwr but that really defeats the purpose of RB and the big memory card. Am I missing the bleeding obvious or is there a tweek I need to do? Thanks in advance. 

[saratoga]

You could try turning off HID mode and maybe also hiding the internal storage in case the USB host on the stereo can't handle them:

https://download.rockbox.org/daily/manual/rockbox-sansae200/rockbox-buildch8.html#x10-1510008.5.8

If that doesn't help, no idea.