I got things working for both C115 and C139 w/ rpi, osmocom built natively on debian and a cheap cp2102 usb raw stick direct from china/ebay.

For C139

./osmocon -d tr -p /dev/ttyUSB0 -m c140xor -c ../../target/firmware/board/compal_e86/rssi.highram.bin

For C115

./osmocon -d tr -p /dev/ttyUSB0 -m c123xor -c ../../target/firmware/board/compal_e88/rssi.highram.bin

Sorry for the trouble... looks like "xor" and chainloading via -c were my two problems.

-Craig