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circuitpython/shared-module/bitbangio/I2C.c

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7.4 KiB

/*
* This file is part of the MicroPython project, http://micropython.org/
*
* The MIT License (MIT)
*
* Copyright (c) 2016 Damien P. George, Scott Shawcroft
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include "shared-bindings/bitbangio/I2C.h"
#include "py/mperrno.h"
#include "py/nlr.h"
#include "py/obj.h"
#include "common-hal/microcontroller/Pin.h"
#include "shared-bindings/microcontroller/__init__.h"
#include "shared-bindings/digitalio/DigitalInOut.h"
#include "shared-module/bitbangio/types.h"
STATIC void delay(bitbangio_i2c_obj_t *self) {
// We need to use an accurate delay to get acceptable I2C
// speeds (eg 1us should be not much more than 1us).
common_hal_mcu_delay_us(self->us_delay);
}
STATIC void scl_low(bitbangio_i2c_obj_t *self) {
common_hal_digitalio_digitalinout_set_value(&self->scl, false);
}
STATIC void scl_release(bitbangio_i2c_obj_t *self) {
common_hal_digitalio_digitalinout_set_value(&self->scl, true);
uint32_t count = self->us_timeout;
delay(self);
// For clock stretching, wait for the SCL pin to be released, with timeout.
for (; !common_hal_digitalio_digitalinout_get_value(&self->scl) && count; --count) {
common_hal_mcu_delay_us(1);
}
if(count==0) { /// raise exception on timeout
nlr_raise(mp_obj_new_exception_msg(&mp_type_TimeoutError,
"Clock Stretching Timeout."));
}
}
STATIC void sda_low(bitbangio_i2c_obj_t *self) {
common_hal_digitalio_digitalinout_set_value(&self->sda, false);
}
STATIC void sda_release(bitbangio_i2c_obj_t *self) {
common_hal_digitalio_digitalinout_set_value(&self->sda, true);
}
STATIC bool sda_read(bitbangio_i2c_obj_t *self) {
common_hal_digitalio_digitalinout_switch_to_input(&self->sda, PULL_UP);
bool value = common_hal_digitalio_digitalinout_get_value(&self->sda);
common_hal_digitalio_digitalinout_switch_to_output(&self->sda, true, DRIVE_MODE_OPEN_DRAIN);
return value;
}
STATIC void start(bitbangio_i2c_obj_t *self) {
sda_release(self);
delay(self);
scl_release(self);
sda_low(self);
delay(self);
}
STATIC void stop(bitbangio_i2c_obj_t *self) {
delay(self);
sda_low(self);
delay(self);
scl_release(self);
sda_release(self);
delay(self);
}
STATIC int write_byte(bitbangio_i2c_obj_t *self, uint8_t val) {
delay(self);
scl_low(self);
for (int i = 7; i >= 0; i--) {
if ((val >> i) & 1) {
sda_release(self);
} else {
sda_low(self);
}
delay(self);
scl_release(self);
scl_low(self);
}
sda_release(self);
delay(self);
scl_release(self);
int ret = sda_read(self);
delay(self);
scl_low(self);
return !ret;
}
STATIC bool read_byte(bitbangio_i2c_obj_t *self, uint8_t *val, bool ack) {
delay(self);
scl_low(self);
delay(self);
uint8_t data = 0;
for (int i = 7; i >= 0; i--) {
scl_release(self);
data = (data << 1) | sda_read(self);
scl_low(self);
delay(self);
}
*val = data;
// send ack/nack bit
if (ack) {
sda_low(self);
}
delay(self);
scl_release(self);
scl_low(self);
sda_release(self);
return true;
}
void shared_module_bitbangio_i2c_construct(bitbangio_i2c_obj_t *self,
const mcu_pin_obj_t * scl,
const mcu_pin_obj_t * sda,
uint32_t frequency,
uint32_t us_timeout) {
self->us_timeout = us_timeout;
self->us_delay = 500000 / frequency;
if (self->us_delay == 0) {
self->us_delay = 1;
}
digitalinout_result_t result = common_hal_digitalio_digitalinout_construct(&self->scl, scl);
if (result != DIGITALINOUT_OK) {
return;
}
result = common_hal_digitalio_digitalinout_construct(&self->sda, sda);
if (result != DIGITALINOUT_OK) {
common_hal_digitalio_digitalinout_deinit(&self->scl);
return;
}
common_hal_digitalio_digitalinout_switch_to_output(&self->scl, true, DRIVE_MODE_OPEN_DRAIN);
common_hal_digitalio_digitalinout_switch_to_output(&self->sda, true, DRIVE_MODE_OPEN_DRAIN);
stop(self);
}
bool shared_module_bitbangio_i2c_deinited(bitbangio_i2c_obj_t *self) {
// If one is deinited, both will be.
return common_hal_digitalio_digitalinout_deinited(&self->scl);
}
void shared_module_bitbangio_i2c_deinit(bitbangio_i2c_obj_t *self) {
if (shared_module_bitbangio_i2c_deinited(self)) {
return;
}
common_hal_digitalio_digitalinout_deinit(&self->scl);
common_hal_digitalio_digitalinout_deinit(&self->sda);
}
bool shared_module_bitbangio_i2c_try_lock(bitbangio_i2c_obj_t *self) {
bool success = false;
common_hal_mcu_disable_interrupts();
if (!self->locked) {
self->locked = true;
success = true;
}
common_hal_mcu_enable_interrupts();
return success;
}
bool shared_module_bitbangio_i2c_has_lock(bitbangio_i2c_obj_t *self) {
return self->locked;
}
void shared_module_bitbangio_i2c_unlock(bitbangio_i2c_obj_t *self) {
self->locked = false;
}
bool shared_module_bitbangio_i2c_probe(bitbangio_i2c_obj_t *self, uint8_t addr) {
start(self);
bool ok = write_byte(self, addr << 1);
stop(self);
return ok;
}
uint8_t shared_module_bitbangio_i2c_write(bitbangio_i2c_obj_t *self, uint16_t addr,
const uint8_t *data, size_t len, bool transmit_stop_bit) {
// start the I2C transaction
start(self);
uint8_t status = 0;
if (!write_byte(self, addr << 1)) {
status = MP_ENODEV;
}
if (status == 0) {
for (uint32_t i = 0; i < len; i++) {
if (!write_byte(self, data[i])) {
status = MP_EIO;
break;
}
}
}
if (transmit_stop_bit) {
stop(self);
}
return status;
}
uint8_t shared_module_bitbangio_i2c_read(bitbangio_i2c_obj_t *self, uint16_t addr,
uint8_t * data, size_t len) {
// start the I2C transaction
start(self);
uint8_t status = 0;
if (!write_byte(self, (addr << 1) | 1)) {
status = MP_ENODEV;
}
if (status == 0) {
for (uint32_t i = 0; i < len; i++) {
if (!read_byte(self, data + i, i < len - 1)) {
status = MP_EIO;
break;
}
}
}
stop(self);
return status;
}