Are you sure the Jam is supported? It seems to me the Sansa Clip Jam != Sansa Clip and the former is not supported at least according to [1]: Sansa Clip Spor

Are you sure the Jam is supported? It seems to me the Sansa Clip Jam != Sansa Clip and the former is not supported at least according to [1]: Sansa Clip Sport / Clip Jam / Clip Sport Go / Clip Sport Plus These are based on an Actions Semiconductor ATJ2127 chips, with under 100KB of available memory and all audio decoding happening inside dedicated hardware. A rockbox port to these (and other ATJ2127) targets will not happen, as it would require an immence undertaking and due to resource limitations, the end result would lack most of the features that rockbox users have come to expect. [1] https://www.rockbox.org/wiki/TargetStatus#New_Platforms_Currently_Under_Development https://www.rockbox.org/wiki/TargetStatus#New_Platforms_Curr...