kopia lustrzana https://github.com/kamocat/uSDX
Drafted decimation filter for qsd receiver
Marshal Horn
rodzic
ace1e657b8
commit
4d55b178a9
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@ -65,21 +65,13 @@
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</folderInfo>
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<folderInfo id="0.87736009.1762812655" name="/" resourcePath="board">
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<sourceEntries>
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<toolChain id="org.eclipse.cdt.build.core.prefbase.toolchain.1198201678" name="No ToolChain" superClass="org.eclipse.cdt.build.core.prefbase.toolchain" unusedChildren="">
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<tool id="org.eclipse.cdt.build.core.settings.holder.libs.117598285" name="holder for library settings" superClass="org.eclipse.cdt.build.core.settings.holder.libs.686764108"/>
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<tool id="org.eclipse.cdt.build.core.settings.holder.1159330235" name="Assembly" superClass="org.eclipse.cdt.build.core.settings.holder.1629275092"/>
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<tool id="org.eclipse.cdt.build.core.settings.holder.1564596667" name="GNU C++" superClass="org.eclipse.cdt.build.core.settings.holder.1369722403"/>
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<tool id="org.eclipse.cdt.build.core.settings.holder.797214978" name="GNU C" superClass="org.eclipse.cdt.build.core.settings.holder.883301168"/>
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</toolChain>
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<entry excluding="radio" flags="VALUE_WORKSPACE_PATH|RESOLVED" kind="sourcePath" name=""/>
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<entry flags="VALUE_WORKSPACE_PATH|RESOLVED" kind="sourcePath" name="radio"/>
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</folderInfo>
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</sourceEntries>
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</configuration>
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@ -120,7 +120,7 @@ LDSCRIPT= $(STARTUPLD)/STM32F051x8.ld
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# setting.
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CSRC = $(ALLCSRC) \
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$(TESTSRC) \
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main.c
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main.c dsp.c radio/rx.c
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# C++ sources that can be compiled in ARM or THUMB mode depending on the global
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# setting.
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@ -0,0 +1,88 @@
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/*
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* dsp.c
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*
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* Created on: Jul 6, 2020
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* Author: marshal
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*/
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#include "dsp.h"
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#include "radio/rx.h"
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/*
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* ADC streaming callback.
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*
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* We sampled at 500kHz, but our bandwidth of interest is only
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* 2kHz. (Since it's quadrature sampling, nyquist rate is 1x)
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* We use a second-order IIR filter to prevent aliasing, followed
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* by an accumulate for decimation
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*/
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static void adccallback(ADCDriver *adcp) {
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adcsample_t * ptr = adcp->samples;
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size_t len = adcp->depth/2; // This also determines downsample ratio
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// These are persistent variables for filter history
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static uint32_t a1 = 0;
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static uint32_t b1 = 0;
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static uint32_t a2 = 0;
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static uint32_t b2 = 0;
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// These are temporary variables to return the downsampled signal
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uint32_t c1 = 0;
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uint32_t c2 = 0;
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/* This determines the corner frequency of our IIR filter.
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* It's actually 1/log2 of the corner
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*/
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const uint8_t corner = 7;
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for(unsigned int i=0; i<len; ++i){
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a1 += *ptr++ - (a1>>corner); // 12+7 = 19 bits
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b1 += a1 - (b1>>corner); // 19+7 = 26 bits
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a2 += *ptr++ - (a2>>corner);
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b2 += a2 - (b2>>corner);
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// If len>64, we need to shift right to prevent overflow.
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const uint8_t shift = 0;
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c1 += b1>>shift; // 26+6=32 bits
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c2 += b2>>shift;
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}
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struct complex c;
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c.real = (c1>>16) - 0x8000;
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c.imag = (c2>>16) - 0x8000;
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chMsgSend((void*)radio_rx, (msg_t)&c);
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}
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static void adcerrorcallback(ADCDriver *adcp, adcerror_t err) {
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(void)adcp;
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(void)err;
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}
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/*
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* ADC conversion group.
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* Mode: Linear buffer, 8 samples of 1 channel, SW triggered.
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* Channels: IN10.
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*/
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static const ADCConversionGroup qsd_in = {
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TRUE, // continuous
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2, // 2 channels
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adccallback,
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adcerrorcallback,
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ADC_CFGR1_RES_12BIT, /* CFGR1 */
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ADC_TR(0, 0), /* TR */
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ADC_SMPR_SMP_1P5, /* SMPR */
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ADC_CHSELR_CHSEL6 | ADC_CHSELR_CHSEL7 /* CHSELR */
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};
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/** ADC init
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*/
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void adc_rx_init(void){
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static char re_init = 0;
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static adcsample_t * samples;
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const int len = 64;
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if(!re_init){
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re_init=1;
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// Allocate MxN buffer for continuous ADC
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samples = chCoreAllocFromBase(
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len * qsd_in.num_channels * sizeof(adcsample_t),
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sizeof(adcsample_t), 0);
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}
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// Start the continuous conversion
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adcStart(&ADCD1, NULL);
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adcStartConversion(&ADCD1, &qsd_in, samples, len);
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}
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@ -0,0 +1,32 @@
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/*
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* dsp.h
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*
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* Created on: Jul 6, 2020
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* Author: marshal
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*/
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#ifndef DSP_H_
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#define DSP_H_
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#include "hal.h"
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#include "ch.h"
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/** ADC streaming callback for radio RX
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*
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* We sampled at 500kHz, but our bandwidth of interest is only
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* 2kHz. (Since it's quadrature sampling, nyquist rate is 1x)
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* We use a second-order IIR filter to prevent aliasing, followed
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* by an accumulate and decimation
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*/
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/** Datatype for complex numbers */
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struct complex{
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int16_t real;
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int16_t imag;
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};
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/** ADC init
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*/
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void adc_rx_init(void);
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#endif /* DSP_H_ */
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@ -0,0 +1,29 @@
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/*
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* rx.c
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*
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* Created on: Jul 6, 2020
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* Author: marshal
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*/
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#include "rx.h"
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#include "dsp.h"
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/** Mailbox for received data */
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msg_t new_sample;
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THD_WORKING_AREA(waradio_rx, 128);
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THD_FUNCTION(radio_rx, arg){
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(void)arg;
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const int len = 256;
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int16_t * data = chCoreAllocFromBase(len*sizeof(int16_t), sizeof(int16_t), 0);
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while(1){
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for( int i=0; i<len;){
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thread_t * thd = chMsgWait();
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struct complex * c = (struct complex *)chMsgGet(thd);
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data[i++] = c->real;
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data[i++] = c->imag;
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chMsgRelease(thd, MSG_OK);
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}
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/** Here would be a good place to do a FFT or other processing */
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}
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}
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@ -0,0 +1,19 @@
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/*
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* rx.h
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*
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* Created on: Jul 6, 2020
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* Author: marshal
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*/
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#ifndef RX_H_
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#define RX_H_
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#include "hal.h"
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#include "ch.h"
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THD_FUNCTION(radio_rx, arg);
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/** Mailbox for received data */
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extern msg_t new_sample;
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#endif /* RX_H_ */
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