diff options
| -rw-r--r-- | host/lib/usrp/cores/rx_dsp_core_3000.cpp | 27 | ||||
| -rw-r--r-- | host/lib/usrp/cores/tx_dsp_core_3000.cpp | 17 | ||||
| -rw-r--r-- | host/lib/usrp/x300/x300_impl.cpp | 8 | ||||
| -rw-r--r-- | host/lib/usrp/x300/x300_impl.hpp | 2 |
4 files changed, 42 insertions, 12 deletions
diff --git a/host/lib/usrp/cores/rx_dsp_core_3000.cpp b/host/lib/usrp/cores/rx_dsp_core_3000.cpp index 18dabade0..035bc6a3f 100644 --- a/host/lib/usrp/cores/rx_dsp_core_3000.cpp +++ b/host/lib/usrp/cores/rx_dsp_core_3000.cpp @@ -173,20 +173,35 @@ public: } } - // Calculate CIC decimation (i.e., without halfband decimators) - // Calculate closest multiplier constant to reverse gain absent scale multipliers + // Caclulate algorithmic gain of CIC for a given decimation. + // For Ettus CIC R=decim, M=1, N=4. Gain = (R * M) ^ N const double rate_pow = std::pow(double(decim & 0xff), 4); - _scaling_adjustment = std::pow(2, ceil_log2(rate_pow))/(1.65*rate_pow); + // Calculate compensation gain values for algorithmic gain of CORDIC and CIC taking into account + // gain compensation blocks already hardcoded in place in DDC (that provide simple 1/2^n gain compensation). + // CORDIC algorithmic gain limits asymptotically around 1.647 after many iterations. + // + // The polar rotation of [I,Q] = [1,1] by Pi/8 also yields max magnitude of SQRT(2) (~1.4142) however + // input to the CORDIC thats outside the unit circle can only be sourced from a saturated RF frontend. + // To provide additional dynamic range head room accordingly using scale factor applied at egress from DDC would + // cost us small signal performance, thus we do no provide compensation gain for a saturated front end and allow + // the signal to clip in the H/W as needed. If we wished to avoid the signal clipping in these circumstances then adjust code to read: + // _scaling_adjustment = std::pow(2, ceil_log2(rate_pow))/(1.648*rate_pow*1.415); + _scaling_adjustment = std::pow(2, ceil_log2(rate_pow))/(1.648*rate_pow); + this->update_scalar(); return _tick_rate/decim_rate; } + // Calculate compensation gain values for algorithmic gain of CORDIC and CIC taking into account + // gain compensation blocks already hardcoded in place in DDC (that provide simple 1/2^n gain compensation). + // Further more factor in OTW format which adds further gain factor to weight output samples correctly. void update_scalar(void){ - const double factor = 1.0 + std::max(ceil_log2(_scaling_adjustment), 0.0); - const double target_scalar = (1 << (_is_b200 ? 17 : 15))*_scaling_adjustment/_dsp_extra_scaling/factor; + const double target_scalar = (1 << (_is_b200 ? 16 : 15))*_scaling_adjustment/_dsp_extra_scaling; const boost::int32_t actual_scalar = boost::math::iround(target_scalar); - _fxpt_scalar_correction = target_scalar/actual_scalar*factor; //should be small + // Calculate the error introduced by using integer representation for the scalar, can be corrected in host later. + _fxpt_scalar_correction = target_scalar/actual_scalar; + // Write DDC with scaling correction for CIC and CORDIC that maximizes dynamic range in 32/16/12/8bits. _iface->poke32(REG_DSP_RX_SCALE_IQ, actual_scalar); } diff --git a/host/lib/usrp/cores/tx_dsp_core_3000.cpp b/host/lib/usrp/cores/tx_dsp_core_3000.cpp index 93b70435f..7e447ae7d 100644 --- a/host/lib/usrp/cores/tx_dsp_core_3000.cpp +++ b/host/lib/usrp/cores/tx_dsp_core_3000.cpp @@ -110,20 +110,25 @@ public: ) % interp_rate % (_tick_rate/1e6) % (rate/1e6); } - // Calculate CIC interpolation (i.e., without halfband interpolators) - // Calculate closest multiplier constant to reverse gain absent scale multipliers + // Caclulate algorithmic gain of CIC for a given interpolation + // For Ettus CIC R=decim, M=1, N=3. Gain = (R * M) ^ N const double rate_pow = std::pow(double(interp & 0xff), 3); - _scaling_adjustment = std::pow(2, ceil_log2(rate_pow))/(1.65*rate_pow); + // Calculate compensation gain values for algorithmic gain of CORDIC and CIC taking into account + // gain compensation blocks already hardcoded in place in DDC (that provide simple 1/2^n gain compensation). + // CORDIC algorithmic gain limits asymptotically around 1.647 after many iterations. + _scaling_adjustment = std::pow(2, ceil_log2(rate_pow))/(1.648*rate_pow); this->update_scalar(); return _tick_rate/interp_rate; } + // Calculate compensation gain values for algorithmic gain of CORDIC and CIC taking into account + // gain compensation blocks already hardcoded in place in DDC (that provide simple 1/2^n gain compensation). + // Further more factor in OTW format which adds further gain factor to weight output samples correctly. void update_scalar(void){ - const double factor = 1.0 + std::max(ceil_log2(_scaling_adjustment), 0.0); - const double target_scalar = (1 << 17)*_scaling_adjustment/_dsp_extra_scaling/factor; + const double target_scalar = (1 << 16)*_scaling_adjustment/_dsp_extra_scaling; const boost::int32_t actual_scalar = boost::math::iround(target_scalar); - _fxpt_scalar_correction = target_scalar/actual_scalar*factor; //should be small + _fxpt_scalar_correction = target_scalar/actual_scalar; //should be small _iface->poke32(REG_DSP_TX_SCALE_IQ, actual_scalar); } diff --git a/host/lib/usrp/x300/x300_impl.cpp b/host/lib/usrp/x300/x300_impl.cpp index f57556a8b..1e424414e 100644 --- a/host/lib/usrp/x300/x300_impl.cpp +++ b/host/lib/usrp/x300/x300_impl.cpp @@ -1334,6 +1334,14 @@ void x300_impl::register_loopback_self_test(wb_iface::sptr iface) UHD_MSG(status) << ((test_fail)? " fail" : "pass") << std::endl; } +void x300_impl::radio_loopback(wb_iface::sptr iface, const bool on) +{ + iface->poke32(radio::sr_addr(radio::LOOPBACK), (on ? 0x1 : 0x0)); + UHD_MSG(status) << ((on)? "Radio Loopback On" : "Radio Loopback Off") << std::endl; +} + + + /*********************************************************************** * clock and time control logic **********************************************************************/ diff --git a/host/lib/usrp/x300/x300_impl.hpp b/host/lib/usrp/x300/x300_impl.hpp index 78c497ad9..1630047af 100644 --- a/host/lib/usrp/x300/x300_impl.hpp +++ b/host/lib/usrp/x300/x300_impl.hpp @@ -250,6 +250,8 @@ private: void register_loopback_self_test(uhd::wb_iface::sptr iface); + void radio_loopback(uhd::wb_iface::sptr iface, const bool on); + /*! \brief Initialize the radio component on a given slot. * * Call this function once per slot (A and B) and motherboard to initialize all the radio components. |