140 lines
4.8 KiB
C
140 lines
4.8 KiB
C
/**
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* Copyright (c) 2021 Raspberry Pi (Trading) Ltd.
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*
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* SPDX-License-Identifier: BSD-3-Clause
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*/
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#include "pio_i2c.h"
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const int PIO_I2C_ICOUNT_LSB = 10;
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const int PIO_I2C_FINAL_LSB = 9;
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const int PIO_I2C_DATA_LSB = 1;
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const int PIO_I2C_NAK_LSB = 0;
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bool pio_i2c_check_error(PIO pio, uint sm) {
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return !!(pio->irq & (1u << sm));
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}
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void pio_i2c_resume_after_error(PIO pio, uint sm) {
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pio_sm_drain_tx_fifo(pio, sm);
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pio_sm_exec(pio, sm, (pio->sm[sm].execctrl & PIO_SM0_EXECCTRL_WRAP_BOTTOM_BITS) >> PIO_SM0_EXECCTRL_WRAP_BOTTOM_LSB);
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pio->irq = 1u << sm;
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}
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void pio_i2c_rx_enable(PIO pio, uint sm, bool en) {
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if (en)
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hw_set_bits(&pio->sm[sm].shiftctrl, PIO_SM0_SHIFTCTRL_AUTOPUSH_BITS);
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else
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hw_clear_bits(&pio->sm[sm].shiftctrl, PIO_SM0_SHIFTCTRL_AUTOPUSH_BITS);
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}
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static inline void pio_i2c_put16(PIO pio, uint sm, uint16_t data) {
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while (pio_sm_is_tx_fifo_full(pio, sm))
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;
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*(io_rw_16 *)&pio->txf[sm] = data;
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}
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// If I2C is ok, block and push data. Otherwise fall straight through.
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void pio_i2c_put_or_err(PIO pio, uint sm, uint16_t data) {
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while (pio_sm_is_tx_fifo_full(pio, sm))
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if (pio_i2c_check_error(pio, sm))
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return;
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if (pio_i2c_check_error(pio, sm))
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return;
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*(io_rw_16 *)&pio->txf[sm] = data;
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}
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uint8_t pio_i2c_get(PIO pio, uint sm) {
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return (uint8_t)pio_sm_get(pio, sm);
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}
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void pio_i2c_start(PIO pio, uint sm) {
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pio_i2c_put_or_err(pio, sm, 1u << PIO_I2C_ICOUNT_LSB); // Escape code for 2 instruction sequence
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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
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pio_i2c_put_or_err(pio, sm, set_scl_sda_program_instructions[I2C_SC0_SD0]); // Also pull clock low so we can present data
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}
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void pio_i2c_stop(PIO pio, uint sm) {
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pio_i2c_put_or_err(pio, sm, 2u << PIO_I2C_ICOUNT_LSB);
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pio_i2c_put_or_err(pio, sm, set_scl_sda_program_instructions[I2C_SC0_SD0]); // SDA is unknown; pull it down
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pio_i2c_put_or_err(pio, sm, set_scl_sda_program_instructions[I2C_SC1_SD0]); // Release clock
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pio_i2c_put_or_err(pio, sm, set_scl_sda_program_instructions[I2C_SC1_SD1]); // Release SDA to return to idle state
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};
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void pio_i2c_repstart(PIO pio, uint sm) {
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pio_i2c_put_or_err(pio, sm, 3u << PIO_I2C_ICOUNT_LSB);
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pio_i2c_put_or_err(pio, sm, set_scl_sda_program_instructions[I2C_SC0_SD1]);
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pio_i2c_put_or_err(pio, sm, set_scl_sda_program_instructions[I2C_SC1_SD1]);
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pio_i2c_put_or_err(pio, sm, set_scl_sda_program_instructions[I2C_SC1_SD0]);
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pio_i2c_put_or_err(pio, sm, set_scl_sda_program_instructions[I2C_SC0_SD0]);
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}
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static void pio_i2c_wait_idle(PIO pio, uint sm) {
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// Finished when TX runs dry or SM hits an IRQ
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pio->fdebug = 1u << (PIO_FDEBUG_TXSTALL_LSB + sm);
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while (!(pio->fdebug & 1u << (PIO_FDEBUG_TXSTALL_LSB + sm) || pio_i2c_check_error(pio, sm)))
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tight_loop_contents();
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}
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int pio_i2c_write_blocking(PIO pio, uint sm, uint8_t addr, uint8_t *txbuf, uint len) {
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int err = 0;
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pio_i2c_start(pio, sm);
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pio_i2c_rx_enable(pio, sm, false);
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pio_i2c_put16(pio, sm, (addr << 2) | 1u);
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while (len && !pio_i2c_check_error(pio, sm)) {
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if (!pio_sm_is_tx_fifo_full(pio, sm)) {
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--len;
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pio_i2c_put_or_err(pio, sm, (*txbuf++ << PIO_I2C_DATA_LSB) | ((len == 0) << PIO_I2C_FINAL_LSB) | 1u);
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}
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}
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pio_i2c_stop(pio, sm);
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pio_i2c_wait_idle(pio, sm);
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if (pio_i2c_check_error(pio, sm)) {
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err = -1;
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pio_i2c_resume_after_error(pio, sm);
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pio_i2c_stop(pio, sm);
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}
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return err;
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}
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int pio_i2c_read_blocking(PIO pio, uint sm, uint8_t addr, uint8_t *rxbuf, uint len) {
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int err = 0;
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pio_i2c_start(pio, sm);
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pio_i2c_rx_enable(pio, sm, true);
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while (!pio_sm_is_rx_fifo_empty(pio, sm))
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(void)pio_i2c_get(pio, sm);
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pio_i2c_put16(pio, sm, (addr << 2) | 3u);
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uint32_t tx_remain = len; // Need to stuff 0xff bytes in to get clocks
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bool first = true;
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while ((tx_remain || len) && !pio_i2c_check_error(pio, sm)) {
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if (tx_remain && !pio_sm_is_tx_fifo_full(pio, sm)) {
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--tx_remain;
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pio_i2c_put16(pio, sm, (0xffu << 1) | (tx_remain ? 0 : (1u << PIO_I2C_FINAL_LSB) | (1u << PIO_I2C_NAK_LSB)));
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}
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if (!pio_sm_is_rx_fifo_empty(pio, sm)) {
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if (first) {
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// Ignore returned address byte
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(void)pio_i2c_get(pio, sm);
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first = false;
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}
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else {
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--len;
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*rxbuf++ = pio_i2c_get(pio, sm);
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}
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}
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}
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pio_i2c_stop(pio, sm);
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pio_i2c_wait_idle(pio, sm);
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if (pio_i2c_check_error(pio, sm)) {
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err = -1;
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pio_i2c_resume_after_error(pio, sm);
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pio_i2c_stop(pio, sm);
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}
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return err;
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}
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