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Wider range of PLL usage #117

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Wider range of PLL usage #117

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14 changes: 9 additions & 5 deletions libtrellis/tools/ecppll.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -29,8 +29,8 @@ f_out = f_vco / output
#define OUTPUT_MAX 400.0f
#define PFD_MIN 3.125f
#define PFD_MAX 400.0f
#define VCO_MIN 400.0f
#define VCO_MAX 800.0f
#define VCO_MIN 60.0f //Experimentally determined 30 MHz, spurious lock at 28 MHz. 60 MHz for safety. Frequency should be kept low to attain lock when using low input frequencies. (VCO = 600 MHz, IN = 12 MHz / 6 = 2 MHz doesn't lock)
#define VCO_MAX 800.0f //Experimentally determined 948 MHz (CLKOP_DIV=79, CLKFB_FIV=25 CLKI_DIV=6)
#include <iostream>
#include <limits>
#include <fstream>
Expand Down Expand Up @@ -277,14 +277,16 @@ void calc_pll_params(pll_params &params, float input, float output){
continue;
for(int feedback_div=1;feedback_div <= 80; feedback_div++){
for(int output_div=1;output_div <= 128; output_div++){
float fvco = fpfd * (float)feedback_div * (float) output_div;
float fvco = fpfd * (float)feedback_div * (float)output_div;

if(fvco < VCO_MIN || fvco > VCO_MAX)
continue;

float fout = fvco / (float) output_div;
if(fabsf(fout - output) < error ||
(fabsf(fout-output) == error && fabsf(fvco - 600) < fabsf(params.fvco - 600))){
(fabsf(fout - output) == error &&
(((fpfd < 4) && fabsf(fvco - 200) < fabsf(params.fvco - 200)) ||
((fpfd >= 4) && fabsf(fvco - 600) < fabsf(params.fvco - 600))))){
error = fabsf(fout-output);
params.refclk_div = input_div;
params.feedback_div = feedback_div;
Expand Down Expand Up @@ -319,7 +321,9 @@ void calc_pll_params_highres(pll_params &params, float input, float output){
for(int secondary_div = 1; secondary_div <= 128; secondary_div++){
float fout = fvco / (float) secondary_div;
if(fabsf(fout - output) < error ||
(fabsf(fout-output) == error && fabsf(fvco - 600) < fabsf(params.fvco - 600))){
(fabsf(fout-output) == error &&
(((fpfd < 4) && fabsf(fvco - 200) < fabsf(params.fvco - 200)) ||
((fpfd >= 4) && fabsf(fvco - 600) < fabsf(params.fvco - 600))))){
error = fabsf(fout-output);
params.mode = pll_mode::HIGHRES;
params.refclk_div = input_div;
Expand Down