Ticket #67 (enhancement)

The Current Situation

Depending on the daughterboard and transmit gain settings, different digital values are required to produce the maximum usable signal. This means that it's impossible to write an application that works on any daughterboard without manually fussing with the maximum usable values sent to the USRP.

Suggestion

From the user's point of view, define a standard digital transmit level that achieves maximum goodness under some condition. That condition is to be determined, but could be something like maximum amplitude that achieves best two-tone IMD or some such.

For each kind of daughterboard figure out the magic value that will scale user provided data to the right internal level for sending as 16-bit I/Q. For sake of argument, assume that user data is scaled such that the reference level corresponds to a single sinusoid with amplitude 1.0, and that the magic scaling takes place behind the scenes in the USRP library.

With that in place, then applications can make adjustments from the +/- 1 values to account for crest factor, multiple simultaneous transmit channels, s/w tx power control, etc.