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106 lines
4.2 KiB
106 lines
4.2 KiB
/*
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* RadioIQMixer_F32.cpp
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*
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* 22 March 2020
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* Bob Larkin, in support of the library:
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* Chip Audette, OpenAudio, Apr 2017
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* -------------------
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* A single signal channel comes in and is multiplied (mixed) with a sin
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* and cos of the same frequency. The pair of mixer outputs are
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* referred to as i and q. The conversion in frequency is either
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* up or down, and a pair of filters on i and q determine which is allow
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* to pass to the output.
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*
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* The sin/cos LO is from synth_sin_cos_f32.cpp See that for details.
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*
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* There are two then two outputs.
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*
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* MIT License, Use at your own risk.
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*/
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#include "RadioIQMixer_F32.h"
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// 513 values of the sine wave in a float array:
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#include "sinTable512_f32.h"
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void RadioIQMixer_F32::update(void) {
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audio_block_f32_t *blockIn, *blockOut_i=NULL, *blockOut_q=NULL;
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uint16_t index, i;
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float32_t a, b, deltaPhase, phaseC;
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// Get first input, i, that will be filtered
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blockIn = AudioStream_F32::receiveWritable_f32(0);
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if (!blockIn) {
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if(errorPrintIQM) Serial.println("IQMIXER-ERR: No input memory");
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return;
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}
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// Try to get a pair of blocks for the IQ output
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blockOut_i = AudioStream_F32::allocate_f32();
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if (!blockOut_i){ // Didn't have any
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if(errorPrintIQM) Serial.println("IQMIXER-ERR: No I output memory");
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AudioStream_F32::release(blockIn);
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return;
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}
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blockOut_q = AudioStream_F32::allocate_f32();
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if (!blockOut_q){
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if(errorPrintIQM) Serial.println("IQMIXER-ERR: No Q output memory");
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AudioStream_F32::release(blockIn);
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AudioStream_F32::release(blockOut_i);
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return;
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}
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// doSimple has amplitude (-1, 1) and sin/cos differ by 90.00 degrees.
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if (doSimple) {
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for (i=0; i < block_size; i++) {
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phaseS += phaseIncrement;
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if (phaseS > 512.0f)
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phaseS -= 512.0f;
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index = (uint16_t) phaseS;
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deltaPhase = phaseS -(float32_t) index;
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/* Read two nearest values of input value from the sin table */
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a = sinTable512_f32[index];
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b = sinTable512_f32[index+1];
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// Linear interpolation and multiplying (DBMixer) with input
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blockOut_i->data[i] = blockIn->data[i] * (a + 0.001953125*(b-a)*deltaPhase);
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/* Repeat for cosine by adding 90 degrees phase */
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index = (index + 128) & 0x01ff;
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/* Read two nearest values of input value from the sin table */
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a = sinTable512_f32[index];
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b = sinTable512_f32[index+1];
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/* deltaPhase will be the same as used for sin */
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blockOut_q->data[i] = blockIn->data[i]*(a + 0.001953125*(b-a)*deltaPhase);
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}
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}
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else { // Do a more flexible update, i.e., not doSimple
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for (i=0; i < block_size; i++) {
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phaseS += phaseIncrement;
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if (phaseS > 512.0f) phaseS -= 512.0f;
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index = (uint16_t) phaseS;
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deltaPhase = phaseS -(float32_t) index;
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/* Read two nearest values of input value from the sin table */
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a = sinTable512_f32[index];
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b = sinTable512_f32[index+1];
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// We now have a sine value, so multiply with the input data and save
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// Linear interpolate sine and multiply with the input and amplitude (about 1.0)
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blockOut_i->data[i] = amplitude_pk * blockIn->data[i] * (a + 0.001953125*(b-a)*deltaPhase);
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/* Shift forward phaseS_C and get cos. First, the calculation of index of the table */
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phaseC = phaseS + phaseS_C;
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if (phaseC > 512.0f) phaseC -= 512.0f;
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index = (uint16_t) phaseC;
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deltaPhase = phaseC -(float32_t) index;
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/* Read two nearest values of input value from the sin table */
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a = sinTable512_f32[index];
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b = sinTable512_f32[index+1];
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// Same as sin, but leave amplitude of LO at +/- 1.0
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blockOut_q->data[i] = blockIn->data[i] * (a + 0.001953125*(b-a)*deltaPhase);
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}
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}
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AudioStream_F32::release(blockIn); // Done with this
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//transmit the data
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AudioStream_F32::transmit(blockOut_i, 0); // send the I outputs
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AudioStream_F32::release(blockOut_i);
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AudioStream_F32::transmit(blockOut_q, 1); // and the Q outputs
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AudioStream_F32::release(blockOut_q);
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}
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