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PIO I2C example: clear ISR counter on each start/repstart #676

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Jul 23, 2025
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PIO I2C example: clear ISR counter on each start/repstart #676

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6 changes: 4 additions & 2 deletions pio/i2c/pio_i2c.c
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Original file line number Diff line number Diff line change
Expand Up @@ -67,9 +67,10 @@ uint8_t pio_i2c_get(PIO pio, uint sm) {
}

void pio_i2c_start(PIO pio, uint sm) {
pio_i2c_put_or_err(pio, sm, 1u << PIO_I2C_ICOUNT_LSB); // Escape code for 2 instruction sequence
pio_i2c_put_or_err(pio, sm, 2u << PIO_I2C_ICOUNT_LSB); // Escape code for 3 instruction sequence
pio_i2c_put_or_err(pio, sm, set_scl_sda_program_instructions[I2C_SC1_SD0]); // We are already in idle state, just pull SDA low
pio_i2c_put_or_err(pio, sm, set_scl_sda_program_instructions[I2C_SC0_SD0]); // Also pull clock low so we can present data
pio_i2c_put_or_err(pio, sm, pio_encode_mov(pio_isr, pio_null)); // Ensure ISR counter is clear following a write
}

void pio_i2c_stop(PIO pio, uint sm) {
Expand All @@ -80,11 +81,12 @@ void pio_i2c_stop(PIO pio, uint sm) {
};

void pio_i2c_repstart(PIO pio, uint sm) {
pio_i2c_put_or_err(pio, sm, 3u << PIO_I2C_ICOUNT_LSB);
pio_i2c_put_or_err(pio, sm, 4u << PIO_I2C_ICOUNT_LSB);
pio_i2c_put_or_err(pio, sm, set_scl_sda_program_instructions[I2C_SC0_SD1]);
pio_i2c_put_or_err(pio, sm, set_scl_sda_program_instructions[I2C_SC1_SD1]);
pio_i2c_put_or_err(pio, sm, set_scl_sda_program_instructions[I2C_SC1_SD0]);
pio_i2c_put_or_err(pio, sm, set_scl_sda_program_instructions[I2C_SC0_SD0]);
pio_i2c_put_or_err(pio, sm, pio_encode_mov(pio_isr, pio_null));
}

static void pio_i2c_wait_idle(PIO pio, uint sm) {
Expand Down