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