sample group packets data payload is always even despite an odd number of channels being configured for that group

The data payload is always a multiple of 32-bits. We only have 16 bits per channel*sample. Thus, the payload is always an even number of channels. If the device is configured to have an odd number of channels active for that sample group then there will be an extra dummy channel in the payload. We should detect when this happens and drop the last dummy channel.