USB streaming still works but USB flash drives no longer recognized?!?

in GROM-USB2P edited December 2016
GROM-USB2P-TOY S/N 844C firmware v87

On one recent cold morning in Chicago, the USB2P no longer recognized the two USB flash drives I keep in my car. Upon insertion, the HU would just show the firmware version 87. Power cycling the system did not help either. 

These flash drives used to play fine for several months. I figured they had frozen and took them inside, but they worked perfectly fine. I then prepared two additional flash drives of a different type, following the format required for the USB2P, but the USB2P did not recognize them either.

Meanwhile, USB streaming from Android continues to work just fine.

Any ideas? Thanks.
  • Playing the USB flash drives started working again. It is unclear whether outside temperature has anything to do with it.

    Sometimes the device enters an inconsistent state where it will skip most of the tracks, going from, say, 11 to 25 to 38, etc. In these cases, the only remedy seems to be a full power cycle (disconnecting the adapter from the HU). Just turning off accessory mode is not enough.

    Maybe firmware version 91 fixes this. Otherwise I will plan to follow up here.
  • Yes I recommend updating firmware to version 91.

    Also make sure you have USB flash drive setup properly.
    The USB flash drive has to be structured in a certain way for it to play on GROM USB.

    Also make sure that the USB flash drive is in FAT file system structure, (i.e. FAT, FAT16 or FAT32)
    NTFS and exFAT is not supported.

    The GROM supports the follow file formats through USB stick

    MP3 layer 1,2,3 bitrate up to 320Kbps
    WMA (no DRM) bitrate up to 384Kbps
    AAC/MP4/iTunes+ (no DRM). Bitrate up to 384Kbps
    OGG/Vorbis bitrate up to 384Kbps
    FLAC up to 24 bits, 48 kHz     ***USB2P/USB3/MST3P/MST4 only

    Make sure also there are no hidden folders and try to keep USB exclusively for music 
    and leave unnecessary files such as Documents and photos off this same USB drive.

    Do NOT have Empty Folders on USB stick as it will cause playback issues for GROM.
    Try also to limit the number of song files within folder to under 299. If need to have more music in "Playlist" then create subfolders within Main folder on USB.

    Make sure Music files in one folder are either all numbered in numerical track order or none number at all in the filename.  Do not have two filenames with same numbering in beginning (i.e. 01trackone.mp3 and 01tracktwo.mp3) as this will confuse GROM which file is considered Track 1.

    Also see if using a FAT file sorter helps.
    Here is one we use with good results

    If you still face issues. I recommend trying a different USB flash drive instead than one you currently are using.
  • Thanks for your detailed and helpful response!

    Again, the USB sticks (several of them) are compliant and were working fine. Then they stopped working when it was really cold. Now they started working again.

    The track skipping problem was also intermittent and went away with a full power cycle.

    Are you saying that a non-compliant USB drive can cause the device to go into an inconsistent state requiring a full power cycle?
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