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Merged
merged 1 commit into from
Oct 3, 2025
+199 −468
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Clean up I2S PIO program selection, automatic swap #3183

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132 changes: 105 additions & 27 deletions libraries/I2S/src/I2S.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -66,6 +66,7 @@
_swapClocks = false;
_multMCLK = 256;
_isSlave = false;
_pgm = nullptr;
}

I2S::~I2S() {
Expand Down Expand Up @@ -262,20 +263,94 @@
pio_sm_set_enabled(_pioMCLK, _smMCLK, true);
}

pio_program_t *I2S::swap2SideSet(const pio_program_t *in) {
int size = (sizeof(*in) + 4) % ~3; // Round up to nearest 32b word for alignment purposes
size += in->length * sizeof(uint16_t);
uint8_t *mem = (uint8_t *)malloc(size);
memcpy(mem, in, sizeof(*in));
pio_program_t *out = (pio_program_t *)mem;
out->instructions = (uint16_t *)(mem + ((sizeof(*in) + 4) % ~3)); // Place the insn memory right after the struct
uint16_t *dest = (uint16_t *)out->instructions;
const uint16_t *src = in->instructions;
for (int i = 0; i < in->length; i++) {
uint16_t insn = src[i];
uint16_t a = (insn & (1 << 12)) >> 1; // Move upper sideset bit down
uint16_t b = (insn & (1 << 11)) << 1; // Move lower sideset bit up
insn &= ~((1 << 12) | (1 << 11));
insn |= a | b;
dest[i] = insn;
}
return out;
}


bool I2S::begin() {
if (_running) {
return false;
}

_running = true;
_hasPeeked = false;
_isHolding = 0;
int off = 0;
if (!_swapClocks) {
if (!_isSlave) {
_i2s = new PIOProgram(_isOutput ? (_isInput ? (_isTDM ? &pio_tdm_inout_program : &pio_i2s_inout_program) : (_isTDM ? &pio_tdm_out_program : (_isLSBJ ? &pio_lsbj_out_program : &pio_i2s_out_program))) : &pio_i2s_in_program);

// Determine the proper base program for the PIO
// Probably should have started API with an enum/bitmask instead of bunch of flags, but we're here now...
const pio_program *pgm;
void (*init)(PIO pio, uint sm, uint offset, uint data_in_pin, uint data_out_pin, uint clock_pin_base, uint bits, uint channels);
const int _SLAVE = 1 << 0;
const int _OUTPUT = 1 << 1;
const int _INPUT = 1 << 2;
const int _TDM = 1 << 3;
const int _LSBJ = 1 << 4;
int selector = (_isSlave ? _SLAVE : 0) | (_isOutput ? _OUTPUT : 0) | (_isInput ? _INPUT : 0) | (_isTDM ? _TDM : 0) | (_isLSBJ ? _LSBJ : 0);
switch (selector) {
case _SLAVE + _OUTPUT:
if (_bps > 16) {
pgm = &pio_i2s_out_slave_32_program;
} else {
_i2s = new PIOProgram(_bps > 16 ? &pio_i2s_out_slave_32_program : &pio_i2s_out_slave_16_program);
pgm = &pio_i2s_out_slave_16_program;
}
init = pio_i2s_out_slave_program_init;
break;
case _OUTPUT + _INPUT + _TDM:
pgm = &pio_tdm_inout_program;
init = pio_tdm_inout_program_init;
break;
case _OUTPUT + _INPUT:
pgm = &pio_i2s_inout_program;
init = pio_i2s_inout_program_init;
break;
case _OUTPUT + _TDM:
pgm = &pio_tdm_out_program;
init = pio_tdm_out_program_init;
break;
case _OUTPUT + _LSBJ:
pgm = &pio_lsbj_out_program;
init = pio_lsbj_out_program_init;
break;
case _OUTPUT:
pgm = &pio_i2s_out_program;
init = pio_i2s_out_program_init;
break;
case _INPUT:
pgm = &pio_i2s_in_program;
init = pio_i2s_in_program_init;
break;
default:
// Unsupported combination!
_running = false;
return false;
}

if (_swapClocks) {
// If we swap, we need to save the generated bits and free on ::end
_pgm = swap2SideSet(pgm);
_i2s = new PIOProgram(_pgm);
} else {
_i2s = new PIOProgram(_isOutput ? (_isInput ? (_isTDM ? &pio_tdm_inout_swap_program : &pio_i2s_inout_swap_program) : (_isTDM ? &pio_tdm_out_swap_program : (_isLSBJ ? &pio_lsbj_out_swap_program : &pio_i2s_out_swap_program))) : &pio_i2s_in_swap_program);
_i2s = new PIOProgram(pgm);
}

// With the RP2350B there is a GPIO-base offset for PIOs, so need to pass the min/max pins to PIOProgram to set appropriately
int minpin, maxpin;
if (_isOutput && _isInput) {
minpin = std::min(std::min((int)_pinDOUT, (int)_pinDIN), (int)_pinBCLK);
Expand All @@ -287,53 +362,48 @@
minpin = std::min((int)_pinDIN, (int)_pinBCLK);
maxpin = std::max((int)_pinDIN, (int)_pinBCLK + 1);
}

int off = 0;
if (!_i2s->prepare(&_pio, &_sm, &off, minpin, maxpin - minpin + 1)) {
_running = false;
free(_pgm);
delete _i2s;
_i2s = nullptr;
return false;
}
if (_isOutput) {
if (_isInput) {
if (_isTDM) {
pio_tdm_inout_program_init(_pio, _sm, off, _pinDIN, _pinDOUT, _pinBCLK, _bps, _swapClocks, _tdmChannels);
} else {
pio_i2s_inout_program_init(_pio, _sm, off, _pinDIN, _pinDOUT, _pinBCLK, _bps, _swapClocks);
}
} else if (_isTDM) {
pio_tdm_out_program_init(_pio, _sm, off, _pinDOUT, _pinBCLK, _bps, _swapClocks, _tdmChannels);
} else if (_isLSBJ) {
pio_lsbj_out_program_init(_pio, _sm, off, _pinDOUT, _pinBCLK, _bps, _swapClocks);
} else {
if (_isSlave) {
pio_i2s_out_slave_program_init(_pio, _sm, off, _pinDOUT, _pinBCLK, _bps, _swapClocks);
} else {
pio_i2s_out_program_init(_pio, _sm, off, _pinDOUT, _pinBCLK, _bps, _swapClocks);
}
}
} else {
pio_i2s_in_program_init(_pio, _sm, off, _pinDIN, _pinBCLK, _bps, _swapClocks);
}

init(_pio, _sm, off, _pinDIN, _pinDOUT, _pinBCLK, _bps, _tdmChannels);

setFrequency(_freq);

// Start MCLK if needed
if (_MCLKenabled) {
MCLKbegin();
}

// Calculate what to send on under/overflow based on the bits
if (_bps == 8) {
uint8_t a = _silenceSample & 0xff;
_silenceSample = (a << 24) | (a << 16) | (a << 8) | a;
} else if (_bps == 16) {
uint16_t a = _silenceSample & 0xffff;
_silenceSample = (a << 16) | a;
}

// Ensure a safe minimum if no buffersize is set
if (!_bufferWords) {
_bufferWords = 64 * (_bps == 32 ? 2 : 1);
}

// Generate the input ARB for DMA to RAM
if (_isInput) {
_arbInput = new AudioBufferManager(_buffers, _bufferWords, _silenceSample, INPUT);
if (!_arbInput->begin(pio_get_dreq(_pio, _sm, false), (volatile void*)&_pio->rxf[_sm])) {
_running = false;
delete _arbInput;
_arbInput = nullptr;
free(_pgm);
_pgm = nullptr;
delete _i2s;
_i2s = nullptr;
return false;
Expand All @@ -344,6 +414,8 @@
_arbInput->setCallback(_cbInput);
}
}

// Generate the output ARB to dump from RAM to I2S
if (_isOutput) {
_arbOutput = new AudioBufferManager(_buffers, _bufferWords, _silenceSample, OUTPUT);
if (!_arbOutput->begin(pio_get_dreq(_pio, _sm, true), &_pio->txf[_sm])) {
Expand All @@ -352,6 +424,8 @@
_arbOutput = nullptr;
delete _arbInput;
_arbInput = nullptr;
free(_pgm);
_pgm = nullptr;
delete _i2s;
_i2s = nullptr;
return false;
Expand All @@ -362,6 +436,8 @@
_arbOutput->setCallback(_cbOutput);
}
}

// Start the ball rolling!
pio_sm_set_enabled(_pio, _sm, true);

return true;
Expand All @@ -380,6 +456,8 @@
_arbOutput = nullptr;
delete _arbInput;
_arbInput = nullptr;
free(_pgm);
_pgm = nullptr;
delete _i2s;
_i2s = nullptr;
}
Expand Down
3 changes: 3 additions & 0 deletions libraries/I2S/src/I2S.h
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Original file line number Diff line number Diff line change
Expand Up @@ -182,11 +182,14 @@ class I2S : public Stream, public AudioOutputBase {

AudioBufferManager *_arbInput;
AudioBufferManager *_arbOutput;
pio_program_t *swap2SideSet(const pio_program_t *src);
pio_program_t *_pgm;
PIOProgram *_i2s;
PIOProgram *_i2sMCLK;
PIO _pio, _pioMCLK;
int _sm, _smMCLK;

static const int I2SSYSCLK_44_1 = 135600; // 44.1, 88.2 kHz sample rates
static const int I2SSYSCLK_8 = 153600; // 8k, 16, 32, 48, 96, 192 kHz

};
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