Cameron/pico-examples
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graham sanderson
2021-01-20 10:49:34 -06:00
commit 46078742c7
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139
pio/i2c/pio_i2c.c Normal file
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/**
* Copyright (c) 2021 Raspberry Pi (Trading) Ltd.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
#include "pio_i2c.h"
const int PIO_I2C_ICOUNT_LSB = 10;
const int PIO_I2C_FINAL_LSB = 9;
const int PIO_I2C_DATA_LSB = 1;
const int PIO_I2C_NAK_LSB = 0;
bool pio_i2c_check_error(PIO pio, uint sm) {
return !!(pio->irq & (1u << sm));
}
void pio_i2c_resume_after_error(PIO pio, uint sm) {
pio_sm_drain_tx_fifo(pio, sm);
pio_sm_exec(pio, sm, (pio->sm[sm].execctrl & PIO_SM0_EXECCTRL_WRAP_BOTTOM_BITS) >> PIO_SM0_EXECCTRL_WRAP_BOTTOM_LSB);
pio->irq = 1u << sm;
}
void pio_i2c_rx_enable(PIO pio, uint sm, bool en) {
if (en)
hw_set_bits(&pio->sm[sm].shiftctrl, PIO_SM0_SHIFTCTRL_AUTOPUSH_BITS);
else
hw_clear_bits(&pio->sm[sm].shiftctrl, PIO_SM0_SHIFTCTRL_AUTOPUSH_BITS);
}
static inline void pio_i2c_put16(PIO pio, uint sm, uint16_t data) {
while (pio_sm_is_tx_fifo_full(pio, sm))
;
*(io_rw_16 *)&pio->txf[sm] = data;
}
// If I2C is ok, block and push data. Otherwise fall straight through.
void pio_i2c_put_or_err(PIO pio, uint sm, uint16_t data) {
while (pio_sm_is_tx_fifo_full(pio, sm))
if (pio_i2c_check_error(pio, sm))
return;
if (pio_i2c_check_error(pio, sm))
return;
*(io_rw_16 *)&pio->txf[sm] = data;
}
uint8_t pio_i2c_get(PIO pio, uint sm) {
return (uint8_t)pio_sm_get(pio, 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, 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
}
void pio_i2c_stop(PIO pio, uint sm) {
pio_i2c_put_or_err(pio, sm, 2u << PIO_I2C_ICOUNT_LSB);
pio_i2c_put_or_err(pio, sm, set_scl_sda_program_instructions[I2C_SC0_SD0]); // SDA is unknown; pull it down
pio_i2c_put_or_err(pio, sm, set_scl_sda_program_instructions[I2C_SC1_SD0]); // Release clock
pio_i2c_put_or_err(pio, sm, set_scl_sda_program_instructions[I2C_SC1_SD1]); // Release SDA to return to idle state
};
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, 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]);
}
static void pio_i2c_wait_idle(PIO pio, uint sm) {
// Finished when TX runs dry or SM hits an IRQ
pio->fdebug = 1u << (PIO_FDEBUG_TXSTALL_LSB + sm);
while (!(pio->fdebug & 1u << (PIO_FDEBUG_TXSTALL_LSB + sm) || pio_i2c_check_error(pio, sm)))
tight_loop_contents();
}
int pio_i2c_write_blocking(PIO pio, uint sm, uint8_t addr, uint8_t *txbuf, uint len) {
int err = 0;
pio_i2c_start(pio, sm);
pio_i2c_rx_enable(pio, sm, false);
pio_i2c_put16(pio, sm, (addr << 2) | 1u);
while (len && !pio_i2c_check_error(pio, sm)) {
if (!pio_sm_is_tx_fifo_full(pio, sm)) {
--len;
pio_i2c_put_or_err(pio, sm, (*txbuf++ << PIO_I2C_DATA_LSB) | ((len == 0) << PIO_I2C_FINAL_LSB) | 1u);
}
}
pio_i2c_stop(pio, sm);
pio_i2c_wait_idle(pio, sm);
if (pio_i2c_check_error(pio, sm)) {
err = -1;
pio_i2c_resume_after_error(pio, sm);
pio_i2c_stop(pio, sm);
}
return err;
}
int pio_i2c_read_blocking(PIO pio, uint sm, uint8_t addr, uint8_t *rxbuf, uint len) {
int err = 0;
pio_i2c_start(pio, sm);
pio_i2c_rx_enable(pio, sm, true);
while (!pio_sm_is_rx_fifo_empty(pio, sm))
(void)pio_i2c_get(pio, sm);
pio_i2c_put16(pio, sm, (addr << 2) | 3u);
uint32_t tx_remain = len; // Need to stuff 0xff bytes in to get clocks
bool first = true;
while ((tx_remain || len) && !pio_i2c_check_error(pio, sm)) {
if (tx_remain && !pio_sm_is_tx_fifo_full(pio, sm)) {
--tx_remain;
pio_i2c_put16(pio, sm, (0xffu << 1) | (tx_remain ? 0 : (1u << PIO_I2C_FINAL_LSB) | (1u << PIO_I2C_NAK_LSB)));
}
if (!pio_sm_is_rx_fifo_empty(pio, sm)) {
if (first) {
// Ignore returned address byte
(void)pio_i2c_get(pio, sm);
first = false;
}
else {
--len;
*rxbuf++ = pio_i2c_get(pio, sm);
}
}
}
pio_i2c_stop(pio, sm);
pio_i2c_wait_idle(pio, sm);
if (pio_i2c_check_error(pio, sm)) {
err = -1;
pio_i2c_resume_after_error(pio, sm);
pio_i2c_stop(pio, sm);
}
return err;
}