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[/] [neo430/] [trunk/] [neo430/] [sw/] [lib/] [neo430/] [source/] [neo430_freq_gen.c] - Blame information for rev 198

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1 198 zero_gravi
// #################################################################################################
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// #  < neo430_freq_gen.c - Frequency Generator helper functions >                                 #
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// # ********************************************************************************************* #
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// # BSD 3-Clause License                                                                          #
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// #                                                                                               #
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// # Copyright (c) 2020, Stephan Nolting. All rights reserved.                                     #
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// #                                                                                               #
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// # Redistribution and use in source and binary forms, with or without modification, are          #
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// # permitted provided that the following conditions are met:                                     #
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// #                                                                                               #
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// # 1. Redistributions of source code must retain the above copyright notice, this list of        #
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// #    conditions and the following disclaimer.                                                   #
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// #                                                                                               #
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// # 2. Redistributions in binary form must reproduce the above copyright notice, this list of     #
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// #    conditions and the following disclaimer in the documentation and/or other materials        #
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// #    provided with the distribution.                                                            #
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// #                                                                                               #
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// # 3. Neither the name of the copyright holder nor the names of its contributors may be used to  #
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// #    endorse or promote products derived from this software without specific prior written      #
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// #    permission.                                                                                #
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// #                                                                                               #
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// # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS   #
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// # OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF               #
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// # MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE    #
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// # COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,     #
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// # EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE #
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// # GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED    #
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// # AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING     #
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// # NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED  #
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// # OF THE POSSIBILITY OF SUCH DAMAGE.                                                            #
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// # ********************************************************************************************* #
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// # The NEO430 Processor - https://github.com/stnolting/neo430                                    #
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// #################################################################################################
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#include "neo430.h"
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#include "neo430_freq_gen.h"
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// Private function prototypes
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static uint32_t neo430_freq_gen_nco_real_output(uint16_t tuning_word, uint16_t prsc_shift);
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/* ------------------------------------------------------------
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 * INFO Enable programmable frequency output channel ch (0..2)
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 * ------------------------------------------------------------ */
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void neo430_freq_gen_enable_ch(uint16_t ch) {
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  if (ch > 2) {
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    return;
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  }
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  FREQ_GEN_CT |= (1 << (FREQ_GEN_CT_CH0_EN+ch));
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}
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/* ------------------------------------------------------------
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 * INFO Disable programmable frequency output channel ch (0..2)
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 * ------------------------------------------------------------ */
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void neo430_freq_gen_disable_ch(uint16_t ch) {
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  if (ch > 2) {
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    return;
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  }
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  FREQ_GEN_CT &= ~(1 << (FREQ_GEN_CT_CH0_EN+ch));
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}
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/* ------------------------------------------------------------
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 * INFO Disable all programmable frequency outputs
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 * ------------------------------------------------------------ */
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void neo430_freq_gen_disable(void) {
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  register uint16_t ct = FREQ_GEN_CT;
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  ct &= ~(1 << FREQ_GEN_CT_CH0_EN);
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  ct &= ~(1 << FREQ_GEN_CT_CH1_EN);
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  ct &= ~(1 << FREQ_GEN_CT_CH2_EN);
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  FREQ_GEN_CT = ct;
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}
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/* ------------------------------------------------------------
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 * INFO Disable all programmable frequency outputs and reset unit
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 * ------------------------------------------------------------ */
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void neo430_freq_gen_reset(void) {
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  FREQ_GEN_CT = 0;
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}
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/* ------------------------------------------------------------
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 * INFO Set frequency programmable frequency output
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 * INFO f_out = ((f_cpu / nco_prsc) * tuning_word[15:0]) / 2^17
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 * WARNING Imprecise due to rounding/truncation errors!
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 * PARAM ch channel to configure (0..2)
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 * PARAM frequency: output frequency in Hz (no fractions possible here)
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 * RETURN the actual output frequency
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 * ------------------------------------------------------------ */
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uint32_t neo430_freq_gen_set_freq(uint16_t ch, uint32_t frequency) {
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  // tuning_word = (f_out * 2^17) / (f_cpu / nco_prsc)
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  uint32_t f_cpu = CLOCKSPEED_32bit;
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  int16_t i;
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  uint16_t prsc_shift = 12; // start with highest prescaler (4096 => 12)
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  if (frequency > (f_cpu/4)) {
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    return 0;
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  }
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  uint64_t freq_tmp;
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  uint32_t freq_real;
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  uint32_t freq_diff;
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  uint32_t freq_diff_best = 0xffffffff; // max
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  uint16_t tuning_word_best = 0;
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  uint16_t prsc_best = 0;
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  uint32_t freq_real_best = 0;
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  // check all possible prescaler
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  for(i=7; i>=0; i--) {
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    freq_tmp = (uint64_t)frequency;
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    freq_tmp = freq_tmp << (17 + prsc_shift); // multiply via bit shifts
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    freq_tmp = freq_tmp / f_cpu;
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    uint16_t tuning_word = (uint16_t)(freq_tmp);
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    // add 1 to tuning word (for rounding issues)
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    freq_real = neo430_freq_gen_nco_real_output(tuning_word+1, prsc_shift);
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    freq_diff = freq_real - frequency;
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    if ((int32_t)freq_diff < 0) {
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      freq_diff = 0 - freq_diff;
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    }
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    // best result yet?
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    if (freq_diff < freq_diff_best) {
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      tuning_word_best = tuning_word;
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      prsc_best = i;
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      freq_diff_best = freq_diff;
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      freq_real_best = freq_real;
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    }
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    // compute next prescaler
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    if ((i == 5) || (i == 3)) {
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      prsc_shift = prsc_shift - 3;
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    }
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    else {
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      prsc_shift = prsc_shift - 1;
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    }
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  }
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  // set tuning word and prescaler
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  neo430_freq_gen_set(ch, tuning_word_best, prsc_best);
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  return freq_real_best;
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}
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/* ------------------------------------------------------------
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 * INFO Compute actual NCO output frequency based on tuning word and prescaler
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 * RETURN the actual output frequency in Hz
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 * ------------------------------------------------------------ */
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static uint32_t neo430_freq_gen_nco_real_output(uint16_t tuning_word, uint16_t prsc_shift) {
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  // f_out = ((f_cpu/nco_prsc) * tuning_word[15:0]) / 2^17
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  uint32_t f_cpu = CLOCKSPEED_32bit;
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  uint64_t f_out = (uint64_t)f_cpu;
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  f_out = f_out * tuning_word;
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  f_out = f_out >> (17 + prsc_shift); // divide by 2^17 * PRSC
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  return (uint32_t)f_out;
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}
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/* ------------------------------------------------------------
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 * INFO Set HW configuration
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 * PARAM ch channel 0,1,2
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 * PARAM 16-bit tuning word
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 * PARAM 3-bit prescaler selector (0,...,7)
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 * ------------------------------------------------------------ */
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void neo430_freq_gen_set(uint16_t ch, uint16_t tuning_word, uint16_t prsc) {
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  // set tuning word and prescaler
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  register uint16_t ctrl = FREQ_GEN_CT;
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  if (ch == 0) {
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    FREQ_GEN_TW_CH0 = tuning_word;
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    ctrl &= ~(0b111 << FREQ_GEN_CT_CH0_PRSC0); // clear old prescaler config
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    ctrl |=  (prsc  << FREQ_GEN_CT_CH0_PRSC0); // set new prescaler config
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  }
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  else if (ch == 1) {
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    FREQ_GEN_TW_CH1 = tuning_word;
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    ctrl &= ~(0b111 << FREQ_GEN_CT_CH1_PRSC0); // clear old prescaler config
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    ctrl |=  (prsc  << FREQ_GEN_CT_CH1_PRSC0); // set new prescaler config
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  }
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  else if (ch == 2) {
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    FREQ_GEN_TW_CH2 = tuning_word;
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    ctrl &= ~(0b111 << FREQ_GEN_CT_CH2_PRSC0); // clear old prescaler config
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    ctrl |=  (prsc  << FREQ_GEN_CT_CH2_PRSC0); // set new prescaler config
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  }
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  FREQ_GEN_CT = ctrl;
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}

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