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-rw-r--r--host/lib/usrp/usrp2/dsp_impl.cpp20
1 files changed, 16 insertions, 4 deletions
diff --git a/host/lib/usrp/usrp2/dsp_impl.cpp b/host/lib/usrp/usrp2/dsp_impl.cpp
index 84314a656..e6e905fdc 100644
--- a/host/lib/usrp/usrp2/dsp_impl.cpp
+++ b/host/lib/usrp/usrp2/dsp_impl.cpp
@@ -52,6 +52,19 @@ static boost::uint32_t calculate_freq_word_and_update_actual_freq(double &freq,
return freq_word;
}
+static boost::uint32_t calculate_cic_word(size_t rate){
+ int hb0 = 0, hb1 = 0;
+ if (rate & 0x1){
+ hb0 = 1;
+ rate /= 2;
+ }
+ if (rate & 0x1){
+ hb1 = 1;
+ rate /= 2;
+ }
+ return (hb1 << 9) | (hb0 << 8) | (rate & 0xff);
+}
+
static boost::uint32_t calculate_iq_scale_word(boost::int16_t i, boost::int16_t q){
return (boost::uint16_t(i) << 16) | (boost::uint16_t(q) << 0);
}
@@ -84,7 +97,7 @@ void usrp2_impl::init_ddc_config(void){
void usrp2_impl::update_ddc_config(void){
//set the decimation
- _iface->poke32(FR_DSP_RX_DECIM_RATE, _ddc_decim);
+ _iface->poke32(FR_DSP_RX_DECIM_RATE, calculate_cic_word(_ddc_decim));
//set the scaling
static const boost::int16_t default_rx_scale_iq = 1024;
@@ -163,15 +176,14 @@ void usrp2_impl::init_duc_config(void){
void usrp2_impl::update_duc_config(void){
// Calculate CIC interpolation (i.e., without halfband interpolators)
- size_t tmp_interp = _duc_interp;
- while(tmp_interp > 128) tmp_interp /= 2;
+ size_t tmp_interp = calculate_cic_word(_duc_interp) & 0xff;
// Calculate closest multiplier constant to reverse gain absent scale multipliers
double interp_cubed = std::pow(double(tmp_interp), 3);
boost::int16_t scale = rint((4096*std::pow(2, ceil(log2(interp_cubed))))/(1.65*interp_cubed));
//set the interpolation
- _iface->poke32(FR_DSP_TX_INTERP_RATE, _ddc_decim);
+ _iface->poke32(FR_DSP_TX_INTERP_RATE, calculate_cic_word(_duc_interp));
//set the scaling
_iface->poke32(FR_DSP_TX_SCALE_IQ, calculate_iq_scale_word(scale, scale));