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Diffstat (limited to 'host/lib/usrp/dsp_utils.hpp')
| -rw-r--r-- | host/lib/usrp/dsp_utils.hpp | 115 |
1 files changed, 115 insertions, 0 deletions
diff --git a/host/lib/usrp/dsp_utils.hpp b/host/lib/usrp/dsp_utils.hpp new file mode 100644 index 000000000..8a6afb292 --- /dev/null +++ b/host/lib/usrp/dsp_utils.hpp @@ -0,0 +1,115 @@ +// +// Copyright 2010 Ettus Research LLC +// +// This program is free software: you can redistribute it and/or modify +// it under the terms of the GNU General Public License as published by +// the Free Software Foundation, either version 3 of the License, or +// (at your option) any later version. +// +// This program is distributed in the hope that it will be useful, +// but WITHOUT ANY WARRANTY; without even the implied warranty of +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +// GNU General Public License for more details. +// +// You should have received a copy of the GNU General Public License +// along with this program. If not, see <http://www.gnu.org/licenses/>. +// + +#ifndef INCLUDED_LIBUHD_USRP_DSP_UTILS_HPP +#define INCLUDED_LIBUHD_USRP_DSP_UTILS_HPP + +#include <uhd/config.hpp> +#include <uhd/utils/assert.hpp> +#include <boost/cstdint.hpp> +#include <boost/math/special_functions/round.hpp> + +namespace uhd{ namespace usrp{ + +namespace dsp_type1{ + + template <class T> T ceil_log2(T num){ + return std::ceil(std::log(num)/std::log(T(2))); + } + + /*! + * Calculate the cordic word from the frequency and clock rate. + * The frequency will be set to the actual (possible) frequency. + * + * \param freq the requested frequency in Hz + * \param codec_rate the dsp codec rate in Hz + * \param the 32-bit cordic control word + */ + static inline boost::uint32_t calc_cordic_word_and_update( + double &freq, + double codec_rate + ){ + UHD_ASSERT_THROW(std::abs(freq) < codec_rate/2.0); + static const double scale_factor = std::pow(2.0, 32); + + //calculate the freq register word + boost::uint32_t freq_word = boost::math::iround((freq / codec_rate) * scale_factor); + + //update the actual frequency + freq = (double(freq_word) / scale_factor) * codec_rate; + + return freq_word; + } + + /*! + * Calculate the CIC filter word from the rate. + * Check if requested decim/interp rate is: + * multiple of 4, enable two halfband filters + * multiple of 2, enable one halfband filter + * handle remainder in CIC + * + * \param rate the requested rate in Sps + * \return the 32-bit cic filter control word + */ + template <typename dsp_rate_type> + static inline boost::uint32_t calc_cic_filter_word(dsp_rate_type rate){ + int hb0 = 0, hb1 = 0; + if (not (rate & 0x1)){ + hb0 = 1; + rate /= 2; + } + if (not (rate & 0x1)){ + hb1 = 1; + rate /= 2; + } + return (hb1 << 9) | (hb0 << 8) | (rate & 0xff); + } + + /*! + * Calculate the IQ scale factor word from I and Q components. + * \param i the I component + * \param q the Q component + * \return the 32-bit scale factor control word + */ + static inline boost::uint32_t calc_iq_scale_word( + boost::int16_t i, + boost::int16_t q + ){ + return (boost::uint16_t(i) << 16) | (boost::uint16_t(q) << 0); + } + + /*! + * Calculate the IQ scale factor word from the rate. + * \param rate the requested rate in Sps + * \return the 32-bit scale factor control word + */ + template <typename dsp_rate_type> + static inline boost::uint32_t calc_iq_scale_word(dsp_rate_type rate){ + // Calculate CIC interpolation (i.e., without halfband interpolators) + dsp_rate_type tmp_rate = calc_cic_filter_word(rate) & 0xff; + + // Calculate closest multiplier constant to reverse gain absent scale multipliers + double rate_cubed = std::pow(double(tmp_rate), 3); + boost::int16_t scale = boost::math::iround((4096*std::pow(2, ceil_log2(rate_cubed)))/(1.65*rate_cubed)); + return calc_iq_scale_word(scale, scale); + } + +} //namespace dsp_type1 + +}} //namespace + +#endif /* INCLUDED_LIBUHD_USRP_DSP_UTILS_HPP */ |