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OpenAudio_ArduinoLibrary/RadioIQMixer_F32.cpp

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/*
* RadioIQMixer_F32.cpp
*
* 22 March 2020
* Bob Larkin, in support of the library:
* Chip Audette, OpenAudio, Apr 2017
* -------------------
* A single signal channel comes in and is multiplied (mixed) with a sin
* and cos of the same frequency. The pair of mixer outputs are
* referred to as i and q. The conversion in frequency is either
* up or down, and a pair of filters on i and q determine which is allow
* to pass to the output.
*
* April 2021 - Alternatively, there can be two inputs to 0 (left) and 1
* (right) feeding the two mixers separately. This covers all transmit
* and receive situations.
*
* The sin/cos LO is from synth_sin_cos_f32.cpp See that for details.
*
* Inputs are either real or I-Q per bool twoChannel. Rev Apr 2021
*
* MIT License, Use at your own risk.
*/
#include "RadioIQMixer_F32.h"
// 513 values of the sine wave in a float array:
#include "sinTable512_f32.h"
void RadioIQMixer_F32::update(void) {
audio_block_f32_t *blockIn0, *blockIn1, *blockOut_i=NULL, *blockOut_q=NULL;
uint16_t index, i;
float32_t a, b, deltaPhase, phaseC;
// Get input block // <<Writable??
blockIn0 = AudioStream_F32::receiveWritable_f32(0);
if (!blockIn0)
return;
if(twoChannel) {
blockIn1 = AudioStream_F32::receiveWritable_f32(1);
if (!blockIn1) {
AudioStream_F32::release(blockIn0);
if(errorPrintIQM) Serial.println("IQMIXER-ERR: No 1 input memory");
return;
}
}
// Try to get a pair of blocks for the IQ output
blockOut_i = AudioStream_F32::allocate_f32();
if (!blockOut_i){ // Didn't have any
if(errorPrintIQM) Serial.println("IQMIXER-ERR: No I output memory");
AudioStream_F32::release(blockIn0);
if(twoChannel)
AudioStream_F32::release(blockIn1);
return;
}
blockOut_q = AudioStream_F32::allocate_f32();
if (!blockOut_q){
if(errorPrintIQM)
Serial.println("IQMIXER-ERR: No Q output memory");
AudioStream_F32::release(blockIn0);
AudioStream_F32::release(blockOut_i);
if(twoChannel)
AudioStream_F32::release(blockIn1);
return;
}
// doSimple has amplitude (-1, 1) and sin/cos differ by 90.00 degrees.
if (doSimple) {
for (i=0; i < block_size; i++) {
phaseS += phaseIncrement;
if (phaseS > 512.0f)
phaseS -= 512.0f;
index = (uint16_t) phaseS;
deltaPhase = phaseS -(float32_t) index;
/* Read two nearest values of input value from the sin table */
a = sinTable512_f32[index];
b = sinTable512_f32[index+1];
// Linear interpolation and multiplying (DBMixer) with input
blockOut_i->data[i] = blockIn0->data[i] * (a + 0.001953125*(b-a)*deltaPhase);
/* Repeat for cosine by adding 90 degrees phase */
index = (index + 128) & 0x01ff;
/* Read two nearest values of input value from the sin table */
a = sinTable512_f32[index];
b = sinTable512_f32[index+1];
/* deltaPhase will be the same as used for sin */
if(twoChannel)
blockOut_q->data[i] = blockIn1->data[i]*(a + 0.001953125*(b-a)*deltaPhase);
else
blockOut_q->data[i] = blockIn0->data[i]*(a + 0.001953125*(b-a)*deltaPhase);
}
}
else { // Do a more flexible update, i.e., not doSimple
for (i=0; i < block_size; i++) {
phaseS += phaseIncrement;
if (phaseS > 512.0f) phaseS -= 512.0f;
index = (uint16_t) phaseS;
deltaPhase = phaseS -(float32_t) index;
/* Read two nearest values of input value from the sin table */
a = sinTable512_f32[index];
b = sinTable512_f32[index+1];
// We now have a sine value, so multiply with the input data and save
// Linear interpolate sine and multiply with the input and amplitude (about 1.0)
blockOut_i->data[i] = amplitude_pk * blockIn0->data[i] * (a + 0.001953125*(b-a)*deltaPhase);
/* Shift forward phaseS_C and get cos. First, the calculation of index of the table */
phaseC = phaseS + phaseS_C;
if (phaseC > 512.0f) phaseC -= 512.0f;
index = (uint16_t) phaseC;
deltaPhase = phaseC -(float32_t) index;
/* Read two nearest values of input value from the sin table */
a = sinTable512_f32[index];
b = sinTable512_f32[index+1];
// Same as sin, but leave amplitude of LO at +/- 1.0
if(twoChannel)
blockOut_q->data[i] = blockIn1->data[i]*(a + 0.001953125*(b-a)*deltaPhase);
else
blockOut_q->data[i] = blockIn0->data[i]*(a + 0.001953125*(b-a)*deltaPhase);
}
}
AudioStream_F32::release(blockIn0); // Done with this
if(twoChannel)
AudioStream_F32::release(blockIn1);
//transmit the data
AudioStream_F32::transmit(blockOut_i, 0); // send the I outputs
AudioStream_F32::release(blockOut_i);
AudioStream_F32::transmit(blockOut_q, 1); // and the Q outputs
AudioStream_F32::release(blockOut_q);
}