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uSDR-pico/dsp.c

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/*
* dsp.c
*
* Created: Mar 2021
* Author: Arjan te Marvelde
*
* Signal processing of RX and TX branch, to be run on the second processor core (CORE1).
*
* The actual DSP engine can be either FFT based in the frequency domain, or in the time domain.
* In dsp.h this can be selected compile-time, by defining the environment variable DSP_FFT.
*
*/
#include "pico/stdlib.h"
#include "pico/multicore.h"
#include "pico/platform.h"
#include "pico/time.h"
#include "pico/sem.h"
#include "hardware/structs/bus_ctrl.h"
#include "hardware/pwm.h"
#include "hardware/adc.h"
#include "hardware/dma.h"
#include "hardware/irq.h"
#include "hardware/timer.h"
#include "hardware/clocks.h"
#include "uSDR.h"
#include "dsp.h"
#include "hmi.h"
#include "fix_fft.h"
volatile bool tx_enabled; // TX branch active
volatile uint32_t dsp_overrun; // Overrun counter
/*
* DAC_RANGE defines PWM cycle, determining DAC resolution and PWM frequency.
* DAC resolution = Vcc / DAC_RANGE
* PWM frequency = Fsys / DAC_RANGE
* A value of 250 means 125MHz/250=500kHz
* ADC is 12 bit, so resolution is by definition 4096
*/
#define DAC_RANGE 256
#define DAC_BIAS (DAC_RANGE/2)
#define ADC_RANGE 4096
#define ADC_BIAS (ADC_RANGE/2)
volatile uint16_t dac_iq, dac_audio;
/*** External Interfaces, mostly used by hmi.c ***/
/*
* MODE is modulation/demodulation
* This setting steers the signal processing branch chosen
*/
volatile int dsp_mode;
void dsp_setmode(int mode)
{
dsp_mode = mode;
}
/*
* S-Meter is based on RSSI, which is in fact the signal level in the preprocessor.
* The length of the (I,Q) vector is taken as reference for RSSI, where
* S value is highest bit set, i.e. RSSI of 512 corresponds with S-9 (S=log2(RSSI))
* This value was calibrated roughly by using the sam antenna and
* comparing an IC R71-E with my uSDR HW implementation and ADC_INT=8.
* +20dB means 10x the S-9 RSSI level, or >5120
* +40dB means 100x the S-9 RSSI level, or >51200
*/
#define S940 51200
#define S930 16180
#define S920 5120
#define S910 1618
#define S9 512
#define S8 256
#define S7 128
#define S6 64
#define S5 32
#define S4 16
#define S3 8
#define S2 4
#define S1 2
volatile uint32_t s_rssi; // 1.. >51200
int get_sval(void)
{
uint32_t s_val = s_rssi;
if (s_val>S940) return(94); // Return max 2 digits!
if (s_val>S930) return(93);
if (s_val>S920) return(92);
if (s_val>S910) return(91);
if (s_val>S9) return(9);
if (s_val>S8) return(8);
if (s_val>S7) return(7);
if (s_val>S6) return(6);
if (s_val>S5) return(5);
if (s_val>S4) return(4);
if (s_val>S3) return(3);
if (s_val>S2) return(2);
return(1);
}
/*
* AGC reference level is log2(0x40) = 6, where 0x40 is the MSB of half DAC_RANGE
* 1/AGC_DECAY and 1/AGC_ATTACK are multipliers before agc_gain value integrator
* These values should ultimately be set by the HMI.
* The time it takes to a gain change is the ( (Set time)/(signal delta) ) / samplerate
* So when delta is 1, and attack is 64, the time is 64/15625 = 4msec (fast attack)
* The decay time is about 100x this value
* Slow attack would be about 4096
*/
#define AGC_REF 6
#define AGC_DECAY 8192
#define AGC_SHORT 64
#define AGC_LONG 4096
#define AGC_DIS 32766
volatile uint16_t agc_decay = AGC_DIS;
volatile uint16_t agc_attack = AGC_DIS;
void dsp_setagc(int agc)
{
switch(agc)
{
case AGC_SLOW:
agc_attack = AGC_LONG;
agc_decay = AGC_DECAY;
break;
case AGC_FAST:
agc_attack = AGC_SHORT;
agc_decay = AGC_DECAY;
break;
default:
agc_attack = AGC_DIS;
agc_decay = AGC_DIS;
break;
}
}
/*
* VOX LINGER is the number msec to wait before releasing TX mode
* The level of detection is derived from the maximum ADC range.
*/
#define VOX_LINGER 500 // 500msec
volatile uint16_t vox_count = 0;
volatile uint16_t vox_level = 0;
volatile bool vox_active; // Is set when audio energy > vox level (and not OFF)
void dsp_setvox(int vox)
{
switch(vox)
{
case VOX_HIGH:
vox_level = ADC_BIAS/2;
break;
case VOX_MEDIUM:
vox_level = ADC_BIAS/4;
break;
case VOX_LOW:
vox_level = ADC_BIAS/16;
break;
default:
vox_level = 0;
vox_count = 0;
break;
}
}
/*** Some handy macro's ***/
#define ABS(x) ( (x)<0 ? -(x) : (x) )
/*
* Calculation of vector length:
* Z = alpha*max(i,q) + beta*min(i,q);
* alpha = 1/1, beta = 3/8 (error<6.8%)
* alpha = 15/16, beta = 15/32 (error<6.25%)
* Better algorithm:
* Z = max( max(i,q), alpha*max(i,q)+beta*min(i,q) )
* alpha = 29/32, beta = 61/128 (error<2.4%)
*/
inline int16_t mag(int16_t i, int16_t q)
{
i = ABS(i); q = ABS(q);
if (i>q)
return (MAX(i,((29*i/32) + (61*q/128))));
else
return (MAX(q,((29*q/32) + (61*i/128))));
}
/*
* Note: A simple regression IIR single pole low pass filter could be made for anti-aliasing.
* y(n) = (1-a)*y(n-1) + a*x(n) = y(n-1) + a*(x(n) - y(n-1))
* in this a = T / (T + R*C)
* Example:
* T is sample period (e.g. 64usec)
* RC the desired RC time: T*(1-a)/a.
* example: a=1/256 : RC = 255*64usec = 16msec (65Hz)
* Alternative faster implementation with higher accuracy
* y(n) = y(n-1) + (x(n) - y(n-1)>>b)
* Here the filtered value is maintained in higher accuracy, i.e. left shifted by b bits.
* Before using the value: y >> b.
* Also, for RC value 1/a = 1<<b, or RC = ((1<<b)-1)*64us
*/
/*** Include the desired DSP engine ***/
#if DSP_FFT == 1
#define AGC_TOP 2047L
#include "dsp_fft.c"
#else
#define AGC_TOP 2047L
#include "dsp_tim.c"
#endif
/** CORE1: ADC IRQ handler **/
/*
* The IRQ handling is redirected to a DMA channel
* This will transfer ADC_INT samples per channel, ADC_INT maximum is 10 (would take 60usec) but safer to use 8
* These are all registers used for the sample acquisition process
*/
#define LSH 8 // Left shift for higher accuracy of level, also LPF
#define ADC_LEVELS (ADC_BIAS/2)<<LSH // Left shifted initial ADC level value
#define BSH 8 // Left shift for higher accuracy of bias, also LPF
#define ADC_BIASS ADC_BIAS<<BSH // Left shifted initial ADC bias value
#define ADC_INT 8 // Nr of samples for integration (max 8, depends on e.g. sample rate)
volatile int16_t adc_sample[ADC_INT][3]; // ADC sample collection, filled by DMA
volatile int32_t adc_bias[3] = {ADC_BIASS, ADC_BIASS, ADC_BIASS}; // ADC dynamic bias (DC) level
volatile int32_t adc_result[3]; // ADC bias-filtered result for further processing
volatile uint32_t adc_level[3] = {ADC_LEVELS, ADC_LEVELS, ADC_LEVELS}; // Signa levels for ADC channels
volatile int adccnt = 0; // Sampling overflow indicator
/** CORE1: DMA IRQ handler **/
// From RP2040 datasheet, DMA Status/Control register layout
// 0x80000000 [31] : AHB_ERROR (0): Logical OR of the READ_ERROR and WRITE_ERROR flags
// 0x40000000 [30] : READ_ERROR (0): If 1, the channel received a read bus error
// 0x20000000 [29] : WRITE_ERROR (0): If 1, the channel received a write bus error
// 0x01000000 [24] : BUSY (0): This flag goes high when the channel starts a new transfer sequence, and low when the...
// 0x00800000 [23] : SNIFF_EN (0): If 1, this channel's data transfers are visible to the sniff hardware, and each...
// 0x00400000 [22] : BSWAP (0): Apply byte-swap transformation to DMA data
// 0x00200000 [21] : IRQ_QUIET (0): In QUIET mode, the channel does not generate IRQs at the end of every transfer block
// 0x001f8000 [20:15] : TREQ_SEL (0): Select a Transfer Request signal
// 0x00007800 [14:11] : CHAIN_TO (0): When this channel completes, it will trigger the channel indicated by CHAIN_TO
// 0x00000400 [10] : RING_SEL (0): Select whether RING_SIZE applies to read or write addresses
// 0x000003c0 [9:6] : RING_SIZE (0): Size of address wrap region
// 0x00000020 [5] : INCR_WRITE (0): If 1, the write address increments with each transfer
// 0x00000010 [4] : INCR_READ (0): If 1, the read address increments with each transfer
// 0x0000000c [3:2] : DATA_SIZE (0): Set the size of each bus transfer (byte/halfword/word)
// 0x00000002 [1] : HIGH_PRIORITY (0): HIGH_PRIORITY gives a channel preferential treatment in issue scheduling: in...
// 0x00000001 [0] : EN (0): DMA Channel Enable
// 0x00120027 (IRQ_QUIET=0x0, TREQ_SEL=0x24, CHAIN_TO=0, INCR_WRITE=1, INCR_READ=0, DATA_SIZE=1, HIGH_PRIORITY=1, EN=1)
/*
* The DMA handler only stops conversions and resets interrupt flag, data is processed in timer callback.
*/
#define CH0 0
#define DMA_CTRL0 0x00120027
void __not_in_flash_func(dma_handler)(void)
{
adc_run(false); // Stop freerunning ADC
dma_hw->ints0 = 1u << CH0; // Clear the interrupt request.
//while (!adc_fifo_is_empty()) adc_fifo_get(); // Empty leftovers from fifo
adccnt++; // ADC overrun indicator increment
}
/** CORE1: Timer callback routine **/
/*
* This runs every TIM_US, i.e. 64usec, and hence determines the actual sample rate
* The filtered samples are set aside, so a new ADC cycle can be started.
* One ADC cycle takes 6usec to complete (3x ADC0..2) + 1x 2usec stray ADC0 conversion.
* The timing is critical, it assumes that the ADC is finished.
* Do not put any other stuff in this callback routine.
*/
semaphore_t dsp_sem;
repeating_timer_t dsp_timer;
volatile int cnt = 4;
volatile int32_t rx_agc = 1, tx_agc = 1; // Factor as AGC
bool __not_in_flash_func(dsp_callback)(repeating_timer_t *t)
{
int32_t temp;
/** Here the rate is: S_RATE=1/TIM_US, assume 15625Hz **/
// Get ADC_INT samples for each channel and correct for DC bias
// LPF RC: ((1<<BSH)-1)*64usec = 16msec
// adc_result is reset every 64usec, adc_bias is not and hence a running average.
adc_result[0] = 0;
adc_result[1] = 0;
adc_result[2] = 0;
for (temp = 0; temp<ADC_INT; temp++)
{
adc_bias[0] += (int32_t)(adc_sample[temp][0]) - (adc_bias[0]>>BSH);
adc_result[0] += (int32_t)(adc_sample[temp][0]) - (adc_bias[0]>>BSH);
adc_bias[1] += (int32_t)(adc_sample[temp][1]) - (adc_bias[1]>>BSH);
adc_result[1] += (int32_t)(adc_sample[temp][1]) - (adc_bias[1]>>BSH);
adc_bias[2] += (int32_t)(adc_sample[temp][2]) - (adc_bias[2]>>BSH);
adc_result[2] += (int32_t)(adc_sample[temp][2]) - (adc_bias[2]>>BSH);
}
// Load new acquisition phase
// So restart ADCs and DMA
adccnt--; // ADC overrun indicator decrement
adc_select_input(0); // Start with ADC0
while (!adc_fifo_is_empty()) adc_fifo_get(); // Empty leftovers from fifo, if any
dma_hw->ch[CH0].read_addr = (io_rw_32)&adc_hw->fifo; // Read from ADC FIFO
dma_hw->ch[CH0].write_addr = (io_rw_32)&adc_sample[0][0]; // Write to sample buffer
dma_hw->ch[CH0].transfer_count = ADC_INT * 3; // Nr of 16 bit words to transfer
dma_hw->ch[CH0].ctrl_trig = DMA_CTRL0; // Write ctrl word while starting the DMA
adc_run(true); // Start ADC too
// Calculate and save signal level, value is left shifted by LSH = 8
// LPF RC: ((1<<LSH)-1)*64usec = 16msec
adc_level[0] += (ABS(adc_result[0]))-(adc_level[0]>>LSH);
adc_level[1] += (ABS(adc_result[1]))-(adc_level[1]>>LSH);
adc_level[2] += (ABS(adc_result[2]))-(adc_level[2]>>LSH);
// Derive RSSI value from RX vector length
// Crude AGC mechanism **NEEDS TO BE IMPROVED**
if (!tx_enabled)
{
// Approximate amplitude, with alpha max + beta min function
uint32_t i=adc_level[1],q=adc_level[0];
if (i>q)
temp = (MAX(i,((29*i/32) + (61*q/128))))>>LSH;
else
temp = (MAX(q,((29*q/32) + (61*i/128))))>>LSH;
s_rssi = MAX(1,temp);
rx_agc = AGC_TOP/s_rssi; // calculate scaling factor
if (rx_agc==0) rx_agc=1;
}
#if DSP_FFT == 1
// Copy samples from/to the right buffers
if (tx_enabled)
{
A_buf[dsp_active][dsp_tick] = (int16_t)(tx_agc*adc_result[2]); // Copy A sample to A buffer
pwm_set_gpio_level(DAC_I, I_buf[dsp_active][dsp_tick] + DAC_BIAS); // Output I to DAC
pwm_set_gpio_level(DAC_Q, Q_buf[dsp_active][dsp_tick] + DAC_BIAS); // Output Q to DAC
}
else
{
I_buf[dsp_active][dsp_tick] = (int16_t)(rx_agc*adc_result[1]); // Copy I sample to I buffer
Q_buf[dsp_active][dsp_tick] = (int16_t)(rx_agc*adc_result[0]); // Copy Q sample to Q buffer
pwm_set_gpio_level(DAC_A, A_buf[dsp_active][dsp_tick] + DAC_BIAS); // Output A to DAC
}
// When I, Q or A buffer is full, move pointer to the next and signal the DSP loop
if (++dsp_tick >= BUFSIZE) // Increment tick and check range
{
dsp_tick = 0; // Reset counter
if (++dsp_active > 2) dsp_active = 0; // Point to next buffer
dsp_overrun++; // Increment overrun counter
sem_release(&dsp_sem); // Signal background processing
}
#else
// Copy samples from/to the right buffers
if (tx_enabled)
{
a_sample = tx_agc * adc_result[2]; // Store A sample for background processing
pwm_set_gpio_level(DAC_I, i_sample); // Output calculated I sample to DAC
pwm_set_gpio_level(DAC_Q, q_sample); // Output calculated Q sample to DAC
}
else
{
q_sample = rx_agc * adc_result[0]; // Store Q sample for background processing
i_sample = rx_agc * adc_result[1]; // Store I sample for background processing
pwm_set_gpio_level(DAC_A, a_sample); // Output calculated A sample to DAC
}
dsp_overrun++; // Increment overrun counter
sem_release(&dsp_sem); // Signal background processing
#endif
return true;
}
/** CORE1: DSP loop, triggered through repeating timer/semaphore **/
void __not_in_flash_func(dsp_loop)()
{
uint32_t cmd;
uint16_t slice_num;
alarm_pool_t *ap;
tx_enabled = false;
vox_active = false;
/*
* Initialize DACs,
* default mode is free running,
* A and B pins are output
*/
gpio_set_function(DAC_Q, GPIO_FUNC_PWM); // GP20 is PWM for Q DAC (Slice 2, Channel A)
gpio_set_function(DAC_I, GPIO_FUNC_PWM); // GP21 is PWM for I DAC (Slice 2, Channel B)
dac_iq = pwm_gpio_to_slice_num(DAC_Q); // Get PWM slice for GP20 (Same for GP21)
pwm_set_clkdiv_int_frac (dac_iq, 1, 0); // clock divide by 1: full system clock
pwm_set_wrap(dac_iq, DAC_RANGE-1); // Set cycle length; nr of counts until wrap, i.e. 125/DAC_RANGE MHz
pwm_set_enabled(dac_iq, true); // Set the PWM running
gpio_set_function(DAC_A, GPIO_FUNC_PWM); // GP22 is PWM for Audio DAC (Slice 3, Channel A)
dac_audio = pwm_gpio_to_slice_num(DAC_A); // Find PWM slice for GP22
pwm_set_clkdiv_int_frac (dac_audio, 1, 0); // clock divide by 1: full system clock
pwm_set_wrap(dac_audio, DAC_RANGE-1); // Set cycle length; nr of counts until wrap, i.e. 125/DAC_RANGE MHz
pwm_set_enabled(dac_audio, true); // Set the PWM running
/*
* Initialize ADCs, use in round robin mode (3 channels)
* samples are stored in array through IRQ callback
*/
adc_init(); // Initialize ADC to known state
adc_gpio_init(ADC_Q); // ADC GPIO for Q channel
adc_gpio_init(ADC_I); // ADC GPIO for I channel
adc_gpio_init(ADC_A); // ADC GPIO for Audio channel
adc_set_round_robin(0x01+0x02+0x04); // Sequence ADC 0-1-2 (GP 26, 27, 28) free running
adc_select_input(0); // Start with ADC0
adc_fifo_setup(true,true,3,false,false); // IRQ result, DMA req, fifo thr=3: xfer per 3 x 16 bits
adc_set_clkdiv(0); // Fastest clock (500 kSps)
/*
* Setup and start DMA channel CH0
*/
dma_channel_set_irq0_enabled(CH0, true); // Raise IRQ line 0 when the channel finishes a block
irq_set_exclusive_handler(DMA_IRQ_0, dma_handler); // Install IRQ handler
irq_set_enabled(DMA_IRQ_0, true); // Enable it
irq_set_priority(DMA_IRQ_0, PICO_HIGHEST_IRQ_PRIORITY); // Prevent race condition with timer
dma_hw->ch[CH0].read_addr = (io_rw_32)&adc_hw->fifo; // Read from ADC FIFO
dma_hw->ch[CH0].write_addr = (io_rw_32)&adc_sample[0][0]; // Write to sample buffer
dma_hw->ch[CH0].transfer_count = ADC_INT * 3; // Nr of 16 bit words to transfer
dma_hw->ch[CH0].ctrl_trig = DMA_CTRL0; // Write ctrl word and start the DMA
adc_run(true); // Also start the ADC
/*
* Use alarm_pool_add_repeating_timer_us() for a core1 associated timer
* First create an alarm pool on core1:
* alarm_pool_t *alarm_pool_create( uint hardware_alarm_num,
* uint max_timers);
* For the core1 alarm pool don't use the default alarm_num (usually 3) but e.g. 1
* Timer callback signals semaphore, while loop blocks on getting it.
* Initialize repeating timer on core1:
* bool alarm_pool_add_repeating_timer_us( alarm_pool_t *pool,
* int64_t delay_us,
* repeating_timer_callback_t callback,
* void *user_data,
* repeating_timer_t *out);
*/
sem_init(&dsp_sem, 0, 1);
ap = alarm_pool_create(1, 4);
alarm_pool_add_repeating_timer_us( ap, -TIM_US, dsp_callback, NULL, &dsp_timer);
dsp_overrun = 0;
// Background processing loop
while(1)
{
sem_acquire_blocking(&dsp_sem); // Wait until timer-callback releases sem
dsp_overrun--; // Decrement overrun counter
// Use adc_level[2] for VOX
if (vox_level == 0) // Only when VOX is enabled
vox_active = false; // Normally false
else
{
if ((adc_level[2]>>LSH) > vox_level) // AND level > limit
{
vox_count = S_RATE * VOX_LINGER / 1000; // While audio present, reset linger timer
vox_active = true; // and keep TX active
}
else if (--vox_count>0) // else decrement linger counter
vox_active = true; // and keep TX active until 0
}
if (tx_enabled) // Use previous setting
{
gpio_put(GP_PTT, false); // Drive PTT low (active)
tx(); // Do TX signal processing
}
else
{
gpio_put(GP_PTT, true); // Drive PTT high (inactive)
rx(); // Do RX signal processing
}
/** !!! This is a trap, ptt remains active after once asserted: TO BE CHECKED! **/
tx_enabled = vox_active || ptt_active; // Check RX or TX
#if DSP_FFT == 1
dsp_tickx = dsp_tick;
#endif
}
}
/** CORE0: Initialize dsp context and spawn CORE1 process **/
void dsp_init()
{
bus_ctrl_hw->priority = BUSCTRL_BUS_PRIORITY_PROC1_BITS; // Set Core 1 prio on bus to high
multicore_launch_core1(dsp_loop); // Start processing on Core 1
}
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