AudioESP32ULP.h

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#pragma once
 
#ifndef ESP32
#error Only the ESP32 supports ULP audio output
#endif
 
#include <driver/dac.h>
#include <driver/rtc_io.h>
#include <esp32/ulp.h>
#include <math.h>
#include <soc/rtc.h>
 
namespace audio_tools {
 
enum UlpDac { ULP_DAC1 = 1, ULP_DAC2 = 2 };
 
class AudioESP32ULP : public AudioOutput {
public:
  AudioInfo defaultConfig() {
    AudioInfo cfg(44100, 2, 16);
    return cfg;
  }
 
  void setMonoDAC(UlpDac dac){
    selected_mono_dac = dac;
  }
 
  void setMinWriteBytes(int bytes){
    min_write_bytes = bytes;
  }
 
  bool begin(AudioInfo info) {
    TRACEI();
    cfg = info;
    stereoOutput = info.channels == 2;
    activeDACs = stereoOutput ? 3 : selected_mono_dac;
    hertz = cfg.sample_rate;
 
    if (info.bits_per_sample != 16) {
      LOGE("Unsupported bits_per_sample: %d", info.bits_per_sample);
      return false;
    }
    return setup();
  }
 
  size_t write(const uint8_t *data, size_t len) {
    TRACED();
    int16_t *data_16 = (int16_t *)data;
    size_t result = 0;
    int16_t stereo[2];
    int frameSize = cfg.channels * sizeof(int16_t);
    int frames = len / frameSize;
    for (int j = 0; j < frames; j++) {
      int pos = j * cfg.channels;
      stereo[0] = data_16[pos];
      stereo[1] = stereoOutput ? data_16[pos + 1] : data_16[pos];
      // blocking write
      while (!writeFrame(stereo)) {
        delay(20);
      }
      result += frameSize;
    }
    return result;
  }
 
  int availableForWrite() {
    int result = totalSampleWords-lastFilledWord;
    return result < min_write_bytes ? 0 : result;
  }
 
  void end() {
    TRACEI();
    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);
    }
  }
 
 
protected:
  int lastFilledWord = 0;
  int hertz;
  int min_write_bytes = 128;
  UlpDac selected_mono_dac = ULP_DAC1;
  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 = 20;
  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;
 
  bool setup() {
    TRACED();
    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 = 134;
    int loopHalfCycles1 = 90;
    int loopHalfCycles2 = 44;
 
    LOGI("Real RTC clock: %d", 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;
    }
 
    LOGI("dt: %d", dt);
    LOGI("dt2: %d", 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
        // load 0x8080 as sample
        I_MOVI(R1, 0x8080), // 6
        // write 0x8080 in the sample buffer
        I_ST(R1, R0, indexAddress), // 8
        // increment the sample index
        I_ADDI(R0, R0, 1), // 6
        // if reached end of the buffer, jump relative to index reset
        I_BGE(-16, 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 writeFrame(int16_t sample[2]) {
    TRACED();
    int16_t ms[2];
    ms[0] = sample[0];
    ms[1] = sample[1];
 
    // 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;
        if (stereoOutput) {
          w = ms[0];
          w |= ms[1] << 8;
        } else {
          w = bufferedOddSample;
          w |= ms[0] << 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;
    }
  }
 
  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);
  }
};
 
}