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Add output via the ULP for the ESP32 (earlephilhower#326)
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Code courtesy of Martin Laclaustra.

Uses the ULP coprocessor on the ESP32 to send samples to the onboard
DACs, freeing the I2S port for other uses.

Connect left output to pin 25, right to pin 26.
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earlephilhower authored Nov 1, 2020
1 parent bbd8748 commit 1c7a2f7
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258 changes: 258 additions & 0 deletions src/AudioOutputULP.cpp
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/*
AudioOutputULP
Outputs to ESP32 DAC through the ULP, freeing I2S for other uses
v 0.0.1 (2020-10-01)
Copyright (C) 2020 Martin Laclaustra, based on bitluni's code
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/

#ifdef ESP32

#include "AudioOutputULP.h"
#include <esp32/ulp.h>
#include <driver/rtc_io.h>
#include <driver/dac.h>
#include <soc/rtc.h>
#include <math.h>

uint32_t create_I_WR_REG(uint32_t reg, uint32_t low_bit, uint32_t high_bit, uint32_t val){
typedef union {ulp_insn_t ulp_ins; uint32_t ulp_bin;} ulp_union;
const ulp_insn_t singleinstruction[] = {I_WR_REG(reg, low_bit, high_bit, val)};
ulp_union recover_ins;
recover_ins.ulp_ins=singleinstruction[0];
return (uint32_t)(recover_ins.ulp_bin);
}

uint32_t create_I_BXI(uint32_t imm_pc){
typedef union {ulp_insn_t ulp_ins; uint32_t ulp_bin;} ulp_union;
const ulp_insn_t singleinstruction[] = {I_BXI(imm_pc)};
ulp_union recover_ins;
recover_ins.ulp_ins=singleinstruction[0];
return (uint32_t)(recover_ins.ulp_bin);
}

bool AudioOutputULP::begin()
{
if(!stereoOutput){
waitingOddSample = false;
//totalSampleWords += 512;
//dacTableStart2 = dacTableStart1;
}

//calculate the actual ULP clock
unsigned long rtc_8md256_period = rtc_clk_cal(RTC_CAL_8MD256, 1000);
unsigned long rtc_fast_freq_hz = 1000000ULL * (1 << RTC_CLK_CAL_FRACT) * 256 / rtc_8md256_period;

//initialize DACs
if(activeDACs & 1){
dac_output_enable(DAC_CHANNEL_1);
dac_output_voltage(DAC_CHANNEL_1, 128);
}
if(activeDACs & 2){
dac_output_enable(DAC_CHANNEL_2);
dac_output_voltage(DAC_CHANNEL_2, 128);
}

int retAddress1 = 9;
int retAddress2 = 14;

int loopCycles = 120;
int loopHalfCycles1 = 76;
int loopHalfCycles2 = 44;

Serial.print("Real RTC clock: ");
Serial.println(rtc_fast_freq_hz);

uint32_t dt = (rtc_fast_freq_hz / hertz) - loopCycles;
uint32_t dt2 = 0;
if(!stereoOutput){
dt = (rtc_fast_freq_hz / hertz) - loopHalfCycles1;
dt2 = (rtc_fast_freq_hz / hertz) - loopHalfCycles2;
}

Serial.print("dt: ");
Serial.println(dt);

Serial.print("dt2: ");
Serial.println(dt2);

const ulp_insn_t stereo[] = {
//reset offset register
I_MOVI(R3, 0),
//delay to get the right sampling rate
I_DELAY(dt), // 6 + dt
//reset sample index
I_MOVI(R0, 0), // 6
//write the index back to memory for the main cpu
I_ST(R0, R3, indexAddress), // 8
//load the samples
I_LD(R1, R0, bufferStart), // 8
//mask the lower 8 bits
I_ANDI(R2, R1, 0x00ff), // 6
//multiply by 2
I_LSHI(R2, R2, 1), // 6
//add start position
I_ADDI(R2, R2, dacTableStart1),// 6
//jump to the dac opcode
I_BXR(R2), // 4
//back from first dac
//delay between the two samples in mono rendering
I_DELAY(dt2), // 6 + dt2
//mask the upper 8 bits
I_ANDI(R2, R1, 0xff00), // 6
//shift the upper bits to right and multiply by 2
I_RSHI(R2, R2, 8 - 1), // 6
//add start position of second dac table
I_ADDI(R2, R2, dacTableStart2),// 6
//jump to the dac opcode
I_BXR(R2), // 4
//here we get back from writing the second sample
//increment the sample index
I_ADDI(R0, R0, 1), // 6
//if reached end of the buffer, jump relative to index reset
I_BGE(-14, totalSampleWords), // 4
//wait to get the right sample rate (2 cycles more to compensate the index reset)
I_DELAY((unsigned int)dt + 2), // 8 + dt
//if not, jump absolute to where index is written to memory
I_BXI(3) // 4
};
// write io and jump back another 12 + 4 + 12 + 4

size_t load_addr = 0;
size_t size = sizeof(stereo)/sizeof(ulp_insn_t);
ulp_process_macros_and_load(load_addr, stereo, &size);
// this is how to get the opcodes
// for(int i = 0; i < size; i++)
// Serial.println(RTC_SLOW_MEM[i], HEX);

//create DAC opcode tables
switch(activeDACs){
case 1:
for(int i = 0; i < 256; i++)
{
RTC_SLOW_MEM[dacTableStart1 + i * 2] = create_I_WR_REG(RTC_IO_PAD_DAC1_REG,19,26,i); //dac1: 0x1D4C0121 | (i << 10)
RTC_SLOW_MEM[dacTableStart1 + 1 + i * 2] = create_I_BXI(retAddress1); // 0x80000000 + retAddress1 * 4
RTC_SLOW_MEM[dacTableStart2 + i * 2] = create_I_WR_REG(RTC_IO_PAD_DAC1_REG,19,26,i); //dac2: 0x1D4C0122 | (i << 10)
RTC_SLOW_MEM[dacTableStart2 + 1 + i * 2] = create_I_BXI(retAddress2); // 0x80000000 + retAddress2 * 4
}
break;
case 2:
for(int i = 0; i < 256; i++)
{
RTC_SLOW_MEM[dacTableStart1 + i * 2] = create_I_WR_REG(RTC_IO_PAD_DAC2_REG,19,26,i); //dac1: 0x1D4C0121 | (i << 10)
RTC_SLOW_MEM[dacTableStart1 + 1 + i * 2] = create_I_BXI(retAddress1); // 0x80000000 + retAddress1 * 4
RTC_SLOW_MEM[dacTableStart2 + i * 2] = create_I_WR_REG(RTC_IO_PAD_DAC2_REG,19,26,i); //dac2: 0x1D4C0122 | (i << 10)
RTC_SLOW_MEM[dacTableStart2 + 1 + i * 2] = create_I_BXI(retAddress2); // 0x80000000 + retAddress2 * 4
}
break;
case 3:
for(int i = 0; i < 256; i++)
{
RTC_SLOW_MEM[dacTableStart1 + i * 2] = create_I_WR_REG(RTC_IO_PAD_DAC1_REG,19,26,i); //dac1: 0x1D4C0121 | (i << 10)
RTC_SLOW_MEM[dacTableStart1 + 1 + i * 2] = create_I_BXI(retAddress1); // 0x80000000 + retAddress1 * 4
RTC_SLOW_MEM[dacTableStart2 + i * 2] = create_I_WR_REG(RTC_IO_PAD_DAC1_REG,19,26,i); //dac2: 0x1D4C0122 | (i << 10)
RTC_SLOW_MEM[dacTableStart2 + 1 + i * 2] = create_I_BXI(retAddress2); // 0x80000000 + retAddress2 * 4
}
break;
}

//set all samples to 128 (silence)
for(int i = 0; i < totalSampleWords; i++)
RTC_SLOW_MEM[bufferStart + i] = 0x8080;

//start
RTC_SLOW_MEM[indexAddress] = 0;
ulp_run(0);

//wait until ULP starts using samples and the index of output sample advances
while(RTC_SLOW_MEM[indexAddress] == 0)
delay(1);

return true;
}

bool AudioOutputULP::ConsumeSample(int16_t sample[2])
{
int16_t ms[2];
ms[0] = sample[0];
ms[1] = sample[1];
MakeSampleStereo16( ms );

// TODO: needs improvement (counting is different here with respect to ULP code)
int currentSample = RTC_SLOW_MEM[indexAddress] & 0xffff;
int currentWord = currentSample >> 1;

for (int i=0; i<2; i++) {
ms[i] = ((ms[i] >> 8) + 128) & 0xff;
}
if(!stereoOutput) // mix both channels
ms[0] = (uint16_t)(( (uint32_t)((int32_t)(ms[0]) + (int32_t)(ms[1])) >> 1 ) & 0xff);

if(waitingOddSample){ // always true for stereo because samples are consumed in pairs
if(lastFilledWord != currentWord) // accept sample if writing index lastFilledWord has not reached index of output sample
{
unsigned int w = ms[0];
if(stereoOutput){
w |= ms[1] << 8;
} else {
w |= bufferedOddSample << 8;
bufferedOddSample = 128;
waitingOddSample = false;
}
RTC_SLOW_MEM[bufferStart + lastFilledWord] = w;
lastFilledWord++;
if(lastFilledWord == totalSampleWords)
lastFilledWord = 0;
return true;
} else {
return false;
}
} else {
bufferedOddSample = ms[0];
waitingOddSample = true;
return true;
}
}


bool AudioOutputULP::stop()
{
audioLogger->printf_P(PSTR("\n\n\nstop\n\n\n"));
const ulp_insn_t stopulp[] = {
//stop the timer
I_END(),
//end the program
I_HALT()};

size_t load_addr = 0;
size_t size = sizeof(stopulp)/sizeof(ulp_insn_t);
ulp_process_macros_and_load(load_addr, stopulp, &size);

//start
ulp_run(0);

if(activeDACs & 1){
dac_output_voltage(DAC_CHANNEL_1, 128);
}
if(activeDACs & 2){
dac_output_voltage(DAC_CHANNEL_2, 128);
}

return true;
}

#endif
63 changes: 63 additions & 0 deletions src/AudioOutputULP.h
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/*
AudioOutputULP
Outputs to ESP32 DAC through the ULP, freeing I2S for other uses
v 0.0.1 (2020-10-01)
Copyright (C) 2020 Martin Laclaustra, based on bitluni's code
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/

// Connect left channel on pin 25
// Connect right channel on pin 26

#ifndef _AUDIOOUTPUTULP_H
#define _AUDIOOUTPUTULP_H

#include "AudioOutput.h"

#ifdef ESP32

class AudioOutputULP : public AudioOutput
{
public:
AudioOutputULP(int argActiveDACs=3) {if(argActiveDACs<1||argActiveDACs>2)argActiveDACs=3;activeDACs=argActiveDACs;stereoOutput=activeDACs==3;};
~AudioOutputULP() {};
virtual bool begin() override;
virtual bool ConsumeSample(int16_t sample[2]) override;
virtual bool stop() override;
enum : int { DAC1 = 1, DAC2 = 2 };
private:
int lastFilledWord = 0;
uint8_t bufferedOddSample = 128;
bool waitingOddSample = true; // must be set to false for mono output
int activeDACs = 3; // 1:DAC1; 2:DAC2; 3:both;
bool stereoOutput = true;
const int opcodeCount = 18;
const uint32_t dacTableStart1 = 2048 - 512;
const uint32_t dacTableStart2 = dacTableStart1 - 512;
uint32_t totalSampleWords = 2048 - 512 - 512 - (opcodeCount + 1); // add 512 for mono
const int totalSamples = totalSampleWords * 2;
const uint32_t indexAddress = opcodeCount;
const uint32_t bufferStart = indexAddress + 1;
};

#else

#error Only the ESP32 supports ULP audio output

#endif

#endif

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