diff options
Diffstat (limited to 'usrp2/host/lib/usrp2_impl.cc')
| -rw-r--r-- | usrp2/host/lib/usrp2_impl.cc | 37 |
1 files changed, 32 insertions, 5 deletions
diff --git a/usrp2/host/lib/usrp2_impl.cc b/usrp2/host/lib/usrp2_impl.cc index 04f50f480..2aa430138 100644 --- a/usrp2/host/lib/usrp2_impl.cc +++ b/usrp2/host/lib/usrp2_impl.cc @@ -46,7 +46,6 @@ #endif static const int DEFAULT_RX_SCALE = 1024; -static const int DEFAULT_TX_SCALE = 3000; namespace usrp2 { @@ -187,9 +186,6 @@ namespace usrp2 { // set workable defaults for scaling if (!set_rx_scale_iq(DEFAULT_RX_SCALE, DEFAULT_RX_SCALE)) std::cerr << "usrp2::ctor set_rx_scale_iq failed\n"; - - if (!set_tx_scale_iq(DEFAULT_TX_SCALE, DEFAULT_TX_SCALE)) - std::cerr << "usrp2::ctor set_tx_scale_iq failed\n"; } usrp2::impl::~impl() @@ -768,11 +764,42 @@ namespace usrp2 { return false; bool success = (ntohx(reply.ok) == 1); - if (success) + if (success) { d_tx_interp = interpolation_factor; + + // Auto-set TX scaling based on interpolation rate + int scale_i, scale_q; + default_tx_scale_iq(d_tx_interp, &scale_i, &scale_q); + return set_tx_scale_iq(scale_i, scale_q); + } + return success; } + void + usrp2::impl::default_tx_scale_iq(int interpolation_factor, int *scale_i, int *scale_q) + { + // Calculate CIC interpolation (i.e., without halfband interpolators) + int i = interpolation_factor; + if (i > 128) + i = i >> 1; + if (i > 128) + i = i >> 1; + + // Calculate dsp_core_tx gain absent scale multipliers + float gain = (1.65*i*i*i)/(4096*pow(2, ceil(log2(i*i*i)))); + + // Calculate closest multiplier constant to reverse gain + int scale = (int)rint(1.0/gain); + // fprintf(stderr, "if=%i i=%i gain=%f scale=%i\n", interpolation_factor, i, gain, scale); + + // Both I and Q are identical in this case + if (scale_i) + *scale_i = scale; + if (scale_q) + *scale_q = scale; + } + bool usrp2::impl::set_tx_scale_iq(int scale_i, int scale_q) { |