/*
 * This file is part of the MicroPython project, http://micropython.org/
 *
 * The MIT License (MIT)
 *
 * Copyright (c) 2016 Damien P. George
 * Copyright (c) Quectel Wireless Solution, Co., Ltd.All Rights Reserved.
 *
 * 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 <stdio.h>
#include <stdint.h>
#include <string.h>

#include "py/mperrno.h"
#include "py/mphal.h"
#include "py/runtime.h"
#include "extmod/machine_i2c.h"

#if MICROPY_PY_MACHINE_I2C

typedef mp_machine_soft_i2c_obj_t machine_i2c_obj_t;

STATIC void mp_hal_i2c_delay(machine_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).
 mp_hal_delay_us_fast(self->us_delay);
}

STATIC void mp_hal_i2c_scl_low(machine_i2c_obj_t *self) {
 mp_hal_pin_od_low(self->scl);
}

STATIC int mp_hal_i2c_scl_release(machine_i2c_obj_t *self) {
 uint32_t count = self->us_timeout;

 mp_hal_pin_od_high(self->scl);
 mp_hal_i2c_delay(self);
 // For clock stretching, wait for the SCL pin to be released, with timeout.
 for (; mp_hal_pin_read(self->scl) == 0 && count; --count) {
 mp_hal_delay_us_fast(1);
 }
 if (count == 0) {
 return -MP_ETIMEDOUT;
 }
 return 0; // success
}

STATIC void mp_hal_i2c_sda_low(machine_i2c_obj_t *self) {
 mp_hal_pin_od_low(self->sda);
}

STATIC void mp_hal_i2c_sda_release(machine_i2c_obj_t *self) {
 mp_hal_pin_od_high(self->sda);
}

STATIC int mp_hal_i2c_sda_read(machine_i2c_obj_t *self) {
 return mp_hal_pin_read(self->sda);
}

STATIC int mp_hal_i2c_start(machine_i2c_obj_t *self) {
 mp_hal_i2c_sda_release(self);
 mp_hal_i2c_delay(self);
 int ret = mp_hal_i2c_scl_release(self);
 if (ret != 0) {
 return ret;
 }
 mp_hal_i2c_sda_low(self);
 mp_hal_i2c_delay(self);
 return 0; // success
}

STATIC int mp_hal_i2c_stop(machine_i2c_obj_t *self) {
 mp_hal_i2c_delay(self);
 mp_hal_i2c_sda_low(self);
 mp_hal_i2c_delay(self);
 int ret = mp_hal_i2c_scl_release(self);
 mp_hal_i2c_sda_release(self);
 mp_hal_i2c_delay(self);
 return ret;
}

STATIC void mp_hal_i2c_init(machine_i2c_obj_t *self, uint32_t freq) {
 self->us_delay = 500000 / freq;
 if (self->us_delay == 0) {
 self->us_delay = 1;
 }
 mp_hal_pin_open_drain(self->scl);
 mp_hal_pin_open_drain(self->sda);
 mp_hal_i2c_stop(self); // ignore error
}

// return value:
// 0 - byte written and ack received
// 1 - byte written and nack received
// <0 - error, with errno being the negative of the return value
STATIC int mp_hal_i2c_write_byte(machine_i2c_obj_t *self, uint8_t val) {
 mp_hal_i2c_delay(self);
 mp_hal_i2c_scl_low(self);

 for (int i = 7; i >= 0; i--) {
 if ((val >> i) & 1) {
 mp_hal_i2c_sda_release(self);
 } else {
 mp_hal_i2c_sda_low(self);
 }
 mp_hal_i2c_delay(self);
 int ret = mp_hal_i2c_scl_release(self);
 if (ret != 0) {
 mp_hal_i2c_sda_release(self);
 return ret;
 }
 mp_hal_i2c_scl_low(self);
 }

 mp_hal_i2c_sda_release(self);
 mp_hal_i2c_delay(self);
 int ret = mp_hal_i2c_scl_release(self);
 if (ret != 0) {
 return ret;
 }

 int ack = mp_hal_i2c_sda_read(self);
 mp_hal_i2c_delay(self);
 mp_hal_i2c_scl_low(self);

 return ack;
}

// return value:
// 0 - success
// <0 - error, with errno being the negative of the return value
STATIC int mp_hal_i2c_read_byte(machine_i2c_obj_t *self, uint8_t *val, int nack) {
 mp_hal_i2c_delay(self);
 mp_hal_i2c_scl_low(self);
 mp_hal_i2c_delay(self);

 uint8_t data = 0;
 for (int i = 7; i >= 0; i--) {
 int ret = mp_hal_i2c_scl_release(self);
 if (ret != 0) {
 return ret;
 }
 data = (data << 1) | mp_hal_i2c_sda_read(self);
 mp_hal_i2c_scl_low(self);
 mp_hal_i2c_delay(self);
 }
 *val = data;

 // send ack/nack bit
 if (!nack) {
 mp_hal_i2c_sda_low(self);
 }
 mp_hal_i2c_delay(self);
 int ret = mp_hal_i2c_scl_release(self);
 if (ret != 0) {
 mp_hal_i2c_sda_release(self);
 return ret;
 }
 mp_hal_i2c_scl_low(self);
 mp_hal_i2c_sda_release(self);

 return 0; // success
}

// return value:
// >=0 - success; for read it's 0, for write it's number of acks received
// <0 - error, with errno being the negative of the return value
int mp_machine_soft_i2c_transfer(mp_obj_base_t *self_in, uint16_t addr, size_t n, mp_machine_i2c_buf_t *bufs, unsigned int flags) {
 machine_i2c_obj_t *self = (machine_i2c_obj_t *)self_in;

 // start the I2C transaction
 int ret = mp_hal_i2c_start(self);
 if (ret != 0) {
 return ret;
 }

 // write the slave address
 ret = mp_hal_i2c_write_byte(self, (addr << 1) | (flags & MP_MACHINE_I2C_FLAG_READ));
 if (ret < 0) {
 return ret;
 } else if (ret != 0) {
 // nack received, release the bus cleanly
 mp_hal_i2c_stop(self);
 return -MP_ENODEV;
 }

 int transfer_ret = 0;
 for (; n--; ++bufs) {
 size_t len = bufs->len;
 uint8_t *buf = bufs->buf;
 if (flags & MP_MACHINE_I2C_FLAG_READ) {
 // read bytes from the slave into the given buffer(s)
 while (len--) {
 ret = mp_hal_i2c_read_byte(self, buf++, (n | len) == 0);
 if (ret != 0) {
 return ret;
 }
 }
 } else {
 // write bytes from the given buffer(s) to the slave
 while (len--) {
 ret = mp_hal_i2c_write_byte(self, *buf++);
 if (ret < 0) {
 return ret;
 } else if (ret != 0) {
 // nack received, stop sending
 n = 0;
 break;
 }
 ++transfer_ret; // count the number of acks
 }
 }
 }

 // finish the I2C transaction
 if (flags & MP_MACHINE_I2C_FLAG_STOP) {
 ret = mp_hal_i2c_stop(self);
 if (ret != 0) {
 return ret;
 }
 }

 return transfer_ret;
}

/******************************************************************************/
// Generic helper functions

// For use by ports that require a single buffer of data for a read/write transfer
int mp_machine_i2c_transfer_adaptor(mp_obj_base_t *self, uint16_t addr, size_t n, mp_machine_i2c_buf_t *bufs, unsigned int flags) {
 size_t len;
 uint8_t *buf;
 if (n == 1) {
 // Use given single buffer
 len = bufs[0].len;
 buf = bufs[0].buf;
 } else {
 // Combine buffers into a single one
 len = 0;
 for (size_t i = 0; i < n; ++i) {
 len += bufs[i].len;
 }
 buf = m_new(uint8_t, len);
 if (!(flags & MP_MACHINE_I2C_FLAG_READ)) {
 len = 0;
 for (size_t i = 0; i < n; ++i) {
 memcpy(buf + len, bufs[i].buf, bufs[i].len);
 len += bufs[i].len;
 }
 }
 }

 mp_machine_i2c_p_t *i2c_p = (mp_machine_i2c_p_t *)self->type->protocol;
 int ret = i2c_p->transfer_single(self, addr, len, buf, flags);

 if (n > 1) {
 if (flags & MP_MACHINE_I2C_FLAG_READ) {
 // Copy data from single buffer to individual ones
 len = 0;
 for (size_t i = 0; i < n; ++i) {
 memcpy(bufs[i].buf, buf + len, bufs[i].len);
 len += bufs[i].len;
 }
 }
 m_del(uint8_t, buf, len);
 }

 return ret;
}

STATIC int mp_machine_i2c_readfrom(mp_obj_base_t *self, uint16_t addr, uint8_t *dest, size_t len, bool stop) {
 mp_machine_i2c_p_t *i2c_p = (mp_machine_i2c_p_t *)self->type->protocol;
 mp_machine_i2c_buf_t buf = {.len = len, .buf = dest};
 unsigned int flags = MP_MACHINE_I2C_FLAG_READ | (stop ? MP_MACHINE_I2C_FLAG_STOP : 0);
 return i2c_p->transfer(self, addr, 1, &buf, flags);
}

STATIC int mp_machine_i2c_writeto(mp_obj_base_t *self, uint16_t addr, const uint8_t *src, size_t len, bool stop) {
 mp_machine_i2c_p_t *i2c_p = (mp_machine_i2c_p_t *)self->type->protocol;
 mp_machine_i2c_buf_t buf = {.len = len, .buf = (uint8_t *)src};
 unsigned int flags = stop ? MP_MACHINE_I2C_FLAG_STOP : 0;
 return i2c_p->transfer(self, addr, 1, &buf, flags);
}

/******************************************************************************/
// MicroPython bindings for generic machine.I2C

STATIC mp_obj_t machine_i2c_init(size_t n_args, const mp_obj_t *args, mp_map_t *kw_args) {
 mp_obj_base_t *self = (mp_obj_base_t *)MP_OBJ_TO_PTR(args[0]);
 mp_machine_i2c_p_t *i2c_p = (mp_machine_i2c_p_t *)self->type->protocol;
 if (i2c_p->init == NULL) {
 mp_raise_msg(&mp_type_OSError, MP_ERROR_TEXT("I2C operation not supported"));
 }
 i2c_p->init(self, n_args - 1, args + 1, kw_args);
 return mp_const_none;
}
MP_DEFINE_CONST_FUN_OBJ_KW(machine_i2c_init_obj, 1, machine_i2c_init);

STATIC mp_obj_t machine_i2c_scan(mp_obj_t self_in) {
 mp_obj_base_t *self = MP_OBJ_TO_PTR(self_in);
 mp_obj_t list = mp_obj_new_list(0, NULL);
 // 7-bit addresses 0b0000xxx and 0b1111xxx are reserved
 for (int addr = 0x08; addr < 0x78; ++addr) {
 int ret = mp_machine_i2c_writeto(self, addr, NULL, 0, true);
 if (ret == 0) {
 mp_obj_list_append(list, MP_OBJ_NEW_SMALL_INT(addr));
 }
 }
 return list;
}
MP_DEFINE_CONST_FUN_OBJ_1(machine_i2c_scan_obj, machine_i2c_scan);

STATIC mp_obj_t machine_i2c_start(mp_obj_t self_in) {
 mp_obj_base_t *self = (mp_obj_base_t *)MP_OBJ_TO_PTR(self_in);
 mp_machine_i2c_p_t *i2c_p = (mp_machine_i2c_p_t *)self->type->protocol;
 if (i2c_p->start == NULL) {
 mp_raise_msg(&mp_type_OSError, MP_ERROR_TEXT("I2C operation not supported"));
 }
 int ret = i2c_p->start(self);
 if (ret != 0) {
 mp_raise_OSError(-ret);
 }
 return mp_const_none;
}
MP_DEFINE_CONST_FUN_OBJ_1(machine_i2c_start_obj, machine_i2c_start);

STATIC mp_obj_t machine_i2c_stop(mp_obj_t self_in) {
 mp_obj_base_t *self = (mp_obj_base_t *)MP_OBJ_TO_PTR(self_in);
 mp_machine_i2c_p_t *i2c_p = (mp_machine_i2c_p_t *)self->type->protocol;
 if (i2c_p->stop == NULL) {
 mp_raise_msg(&mp_type_OSError, MP_ERROR_TEXT("I2C operation not supported"));
 }
 int ret = i2c_p->stop(self);
 if (ret != 0) {
 mp_raise_OSError(-ret);
 }
 return mp_const_none;
}
MP_DEFINE_CONST_FUN_OBJ_1(machine_i2c_stop_obj, machine_i2c_stop);

STATIC mp_obj_t machine_i2c_readinto(size_t n_args, const mp_obj_t *args) {
 mp_obj_base_t *self = (mp_obj_base_t *)MP_OBJ_TO_PTR(args[0]);
 mp_machine_i2c_p_t *i2c_p = (mp_machine_i2c_p_t *)self->type->protocol;
 if (i2c_p->read == NULL) {
 mp_raise_msg(&mp_type_OSError, MP_ERROR_TEXT("I2C operation not supported"));
 }

 // get the buffer to read into
 mp_buffer_info_t bufinfo;
 mp_get_buffer_raise(args[1], &bufinfo, MP_BUFFER_WRITE);

 // work out if we want to send a nack at the end
 bool nack = (n_args == 2) ? true : mp_obj_is_true(args[2]);

 // do the read
 int ret = i2c_p->read(self, bufinfo.buf, bufinfo.len, nack);
 if (ret != 0) {
 mp_raise_OSError(-ret);
 }

 return mp_const_none;
}
MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(machine_i2c_readinto_obj, 2, 3, machine_i2c_readinto);

STATIC mp_obj_t machine_i2c_write(mp_obj_t self_in, mp_obj_t buf_in) {
 mp_obj_base_t *self = (mp_obj_base_t *)MP_OBJ_TO_PTR(self_in);
 mp_machine_i2c_p_t *i2c_p = (mp_machine_i2c_p_t *)self->type->protocol;
 if (i2c_p->write == NULL) {
 mp_raise_msg(&mp_type_OSError, MP_ERROR_TEXT("I2C operation not supported"));
 }

 // get the buffer to write from
 mp_buffer_info_t bufinfo;
 mp_get_buffer_raise(buf_in, &bufinfo, MP_BUFFER_READ);

 // do the write
 int ret = i2c_p->write(self, bufinfo.buf, bufinfo.len);
 if (ret < 0) {
 mp_raise_OSError(-ret);
 }

 // return number of acks received
 return MP_OBJ_NEW_SMALL_INT(ret);
}
MP_DEFINE_CONST_FUN_OBJ_2(machine_i2c_write_obj, machine_i2c_write);

STATIC mp_obj_t machine_i2c_readfrom(size_t n_args, const mp_obj_t *args) {
 mp_obj_base_t *self = (mp_obj_base_t *)MP_OBJ_TO_PTR(args[0]);
 mp_int_t addr = mp_obj_get_int(args[1]);
 vstr_t vstr;
 vstr_init_len(&vstr, mp_obj_get_int(args[2]));
 bool stop = (n_args == 3) ? true : mp_obj_is_true(args[3]);
 int ret = mp_machine_i2c_readfrom(self, addr, (uint8_t *)vstr.buf, vstr.len, stop);
 if (ret < 0) {
 mp_raise_OSError(-ret);
 }
 return mp_obj_new_str_from_vstr(&mp_type_bytes, &vstr);
}
MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(machine_i2c_readfrom_obj, 3, 4, machine_i2c_readfrom);

STATIC mp_obj_t machine_i2c_readfrom_into(size_t n_args, const mp_obj_t *args) {
 mp_obj_base_t *self = (mp_obj_base_t *)MP_OBJ_TO_PTR(args[0]);
 mp_int_t addr = mp_obj_get_int(args[1]);
 mp_buffer_info_t bufinfo;
 mp_get_buffer_raise(args[2], &bufinfo, MP_BUFFER_WRITE);
 bool stop = (n_args == 3) ? true : mp_obj_is_true(args[3]);
 int ret = mp_machine_i2c_readfrom(self, addr, bufinfo.buf, bufinfo.len, stop);
 if (ret < 0) {
 mp_raise_OSError(-ret);
 }
 return mp_const_none;
}
MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(machine_i2c_readfrom_into_obj, 3, 4, machine_i2c_readfrom_into);

STATIC mp_obj_t machine_i2c_writeto(size_t n_args, const mp_obj_t *args) {
 mp_obj_base_t *self = (mp_obj_base_t *)MP_OBJ_TO_PTR(args[0]);
 mp_int_t addr = mp_obj_get_int(args[1]);
 mp_buffer_info_t bufinfo;
 mp_get_buffer_raise(args[2], &bufinfo, MP_BUFFER_READ);
 bool stop = (n_args == 3) ? true : mp_obj_is_true(args[3]);
 int ret = mp_machine_i2c_writeto(self, addr, bufinfo.buf, bufinfo.len, stop);
 if (ret < 0) {
 mp_raise_OSError(-ret);
 }
 // return number of acks received
 return MP_OBJ_NEW_SMALL_INT(ret);
}
STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(machine_i2c_writeto_obj, 3, 4, machine_i2c_writeto);

STATIC mp_obj_t machine_i2c_writevto(size_t n_args, const mp_obj_t *args) {
 mp_obj_base_t *self = (mp_obj_base_t *)MP_OBJ_TO_PTR(args[0]);
 mp_int_t addr = mp_obj_get_int(args[1]);

 // Get the list of data buffer(s) to write
 size_t nitems;
 const mp_obj_t *items;
 mp_obj_get_array(args[2], &nitems, (mp_obj_t **)&items);

 // Get the stop argument
 bool stop = (n_args == 3) ? true : mp_obj_is_true(args[3]);

 // Extract all buffer data, skipping zero-length buffers
 size_t alloc = nitems == 0 ? 1 : nitems;
 size_t nbufs = 0;
 mp_machine_i2c_buf_t *bufs = mp_local_alloc(alloc * sizeof(mp_machine_i2c_buf_t));
 for (; nitems--; ++items) {
 mp_buffer_info_t bufinfo;
 mp_get_buffer_raise(*items, &bufinfo, MP_BUFFER_READ);
 if (bufinfo.len > 0) {
 bufs[nbufs].len = bufinfo.len;
 bufs[nbufs++].buf = bufinfo.buf;
 }
 }

 // Make sure there is at least one buffer, empty if needed
 if (nbufs == 0) {
 bufs[0].len = 0;
 bufs[0].buf = NULL;
 nbufs = 1;
 }

 // Do the I2C transfer
 mp_machine_i2c_p_t *i2c_p = (mp_machine_i2c_p_t *)self->type->protocol;
 int ret = i2c_p->transfer(self, addr, nbufs, bufs, stop ? MP_MACHINE_I2C_FLAG_STOP : 0);
 mp_local_free(bufs);

 if (ret < 0) {
 mp_raise_OSError(-ret);
 }

 // Return number of acks received
 return MP_OBJ_NEW_SMALL_INT(ret);
}
STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(machine_i2c_writevto_obj, 3, 4, machine_i2c_writevto);

STATIC size_t fill_memaddr_buf(uint8_t *memaddr_buf, uint32_t memaddr, uint8_t addrsize) {
 size_t memaddr_len = 0;
 if ((addrsize & 7) != 0 || addrsize > 32) {
 mp_raise_ValueError(MP_ERROR_TEXT("invalid addrsize"));
 }
 for (int16_t i = addrsize - 8; i >= 0; i -= 8) {
 memaddr_buf[memaddr_len++] = memaddr >> i;
 }
 return memaddr_len;
}

STATIC int read_mem(mp_obj_t self_in, uint16_t addr, uint32_t memaddr, uint8_t addrsize, uint8_t *buf, size_t len) {
 mp_obj_base_t *self = (mp_obj_base_t *)MP_OBJ_TO_PTR(self_in);

 // Create buffer with memory address
 uint8_t memaddr_buf[4];
 size_t memaddr_len = fill_memaddr_buf(&memaddr_buf[0], memaddr, addrsize);

 int ret = mp_machine_i2c_writeto(self, addr, memaddr_buf, memaddr_len, false);
 if (ret != memaddr_len) {
 // must generate STOP
 mp_machine_i2c_writeto(self, addr, NULL, 0, true);
 return ret;
 }
 return mp_machine_i2c_readfrom(self, addr, buf, len, true);
}

STATIC int write_mem(mp_obj_t self_in, uint16_t addr, uint32_t memaddr, uint8_t addrsize, const uint8_t *buf, size_t len) {
 mp_obj_base_t *self = (mp_obj_base_t *)MP_OBJ_TO_PTR(self_in);

 // Create buffer with memory address
 uint8_t memaddr_buf[4];
 size_t memaddr_len = fill_memaddr_buf(&memaddr_buf[0], memaddr, addrsize);

 // Create partial write buffers
 mp_machine_i2c_buf_t bufs[2] = {
 {.len = memaddr_len, .buf = memaddr_buf},
 {.len = len, .buf = (uint8_t *)buf},
 };

 // Do I2C transfer
 mp_machine_i2c_p_t *i2c_p = (mp_machine_i2c_p_t *)self->type->protocol;
 return i2c_p->transfer(self, addr, 2, bufs, MP_MACHINE_I2C_FLAG_STOP);
}

STATIC const mp_arg_t machine_i2c_mem_allowed_args[] = {
 { MP_QSTR_addr, MP_ARG_REQUIRED | MP_ARG_INT, {.u_int = 0} },
 { MP_QSTR_memaddr, MP_ARG_REQUIRED | MP_ARG_INT, {.u_int = 0} },
 { MP_QSTR_arg, MP_ARG_REQUIRED | MP_ARG_OBJ, {.u_obj = MP_OBJ_NULL} },
 { MP_QSTR_addrsize, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 8} },
};

STATIC mp_obj_t machine_i2c_readfrom_mem(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
 enum { ARG_addr, ARG_memaddr, ARG_n, ARG_addrsize };
 mp_arg_val_t args[MP_ARRAY_SIZE(machine_i2c_mem_allowed_args)];
 mp_arg_parse_all(n_args - 1, pos_args + 1, kw_args,
 MP_ARRAY_SIZE(machine_i2c_mem_allowed_args), machine_i2c_mem_allowed_args, args);

 // create the buffer to store data into
 vstr_t vstr;
 vstr_init_len(&vstr, mp_obj_get_int(args[ARG_n].u_obj));

 // do the transfer
 int ret = read_mem(pos_args[0], args[ARG_addr].u_int, args[ARG_memaddr].u_int,
 args[ARG_addrsize].u_int, (uint8_t *)vstr.buf, vstr.len);
 if (ret < 0) {
 mp_raise_OSError(-ret);
 }

 return mp_obj_new_str_from_vstr(&mp_type_bytes, &vstr);
}
MP_DEFINE_CONST_FUN_OBJ_KW(machine_i2c_readfrom_mem_obj, 1, machine_i2c_readfrom_mem);


STATIC mp_obj_t machine_i2c_readfrom_mem_into(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
 enum { ARG_addr, ARG_memaddr, ARG_buf, ARG_addrsize };
 mp_arg_val_t args[MP_ARRAY_SIZE(machine_i2c_mem_allowed_args)];
 mp_arg_parse_all(n_args - 1, pos_args + 1, kw_args,
 MP_ARRAY_SIZE(machine_i2c_mem_allowed_args), machine_i2c_mem_allowed_args, args);

 // get the buffer to store data into
 mp_buffer_info_t bufinfo;
 mp_get_buffer_raise(args[ARG_buf].u_obj, &bufinfo, MP_BUFFER_WRITE);

 // do the transfer
 int ret = read_mem(pos_args[0], args[ARG_addr].u_int, args[ARG_memaddr].u_int,
 args[ARG_addrsize].u_int, bufinfo.buf, bufinfo.len);
 if (ret < 0) {
 mp_raise_OSError(-ret);
 }
 return mp_const_none;
}
MP_DEFINE_CONST_FUN_OBJ_KW(machine_i2c_readfrom_mem_into_obj, 1, machine_i2c_readfrom_mem_into);

STATIC mp_obj_t machine_i2c_writeto_mem(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
 enum { ARG_addr, ARG_memaddr, ARG_buf, ARG_addrsize };
 mp_arg_val_t args[MP_ARRAY_SIZE(machine_i2c_mem_allowed_args)];
 mp_arg_parse_all(n_args - 1, pos_args + 1, kw_args,
 MP_ARRAY_SIZE(machine_i2c_mem_allowed_args), machine_i2c_mem_allowed_args, args);

 // get the buffer to write the data from
 mp_buffer_info_t bufinfo;
 mp_get_buffer_raise(args[ARG_buf].u_obj, &bufinfo, MP_BUFFER_READ);

 // do the transfer
 int ret = write_mem(pos_args[0], args[ARG_addr].u_int, args[ARG_memaddr].u_int,
 args[ARG_addrsize].u_int, bufinfo.buf, bufinfo.len);
 if (ret < 0) {
 mp_raise_OSError(-ret);
 }

 return mp_const_none;
}
STATIC MP_DEFINE_CONST_FUN_OBJ_KW(machine_i2c_writeto_mem_obj, 1, machine_i2c_writeto_mem);

STATIC const mp_rom_map_elem_t machine_i2c_locals_dict_table[] = {
 { MP_ROM_QSTR(MP_QSTR_init), MP_ROM_PTR(&machine_i2c_init_obj) },
 { MP_ROM_QSTR(MP_QSTR_scan), MP_ROM_PTR(&machine_i2c_scan_obj) },

 // primitive I2C operations
 { MP_ROM_QSTR(MP_QSTR_start), MP_ROM_PTR(&machine_i2c_start_obj) },
 { MP_ROM_QSTR(MP_QSTR_stop), MP_ROM_PTR(&machine_i2c_stop_obj) },
 { MP_ROM_QSTR(MP_QSTR_readinto), MP_ROM_PTR(&machine_i2c_readinto_obj) },
 { MP_ROM_QSTR(MP_QSTR_write), MP_ROM_PTR(&machine_i2c_write_obj) },

 // standard bus operations
 { MP_ROM_QSTR(MP_QSTR_readfrom), MP_ROM_PTR(&machine_i2c_readfrom_obj) },
 { MP_ROM_QSTR(MP_QSTR_readfrom_into), MP_ROM_PTR(&machine_i2c_readfrom_into_obj) },
 { MP_ROM_QSTR(MP_QSTR_writeto), MP_ROM_PTR(&machine_i2c_writeto_obj) },
 { MP_ROM_QSTR(MP_QSTR_writevto), MP_ROM_PTR(&machine_i2c_writevto_obj) },

 // memory operations
 { MP_ROM_QSTR(MP_QSTR_readfrom_mem), MP_ROM_PTR(&machine_i2c_readfrom_mem_obj) },
 { MP_ROM_QSTR(MP_QSTR_readfrom_mem_into), MP_ROM_PTR(&machine_i2c_readfrom_mem_into_obj) },
 { MP_ROM_QSTR(MP_QSTR_writeto_mem), MP_ROM_PTR(&machine_i2c_writeto_mem_obj) },
};
MP_DEFINE_CONST_DICT(mp_machine_i2c_locals_dict, machine_i2c_locals_dict_table);

/******************************************************************************/
// Implementation of soft I2C

STATIC void mp_machine_soft_i2c_print(const mp_print_t *print, mp_obj_t self_in, mp_print_kind_t kind) {
 mp_machine_soft_i2c_obj_t *self = MP_OBJ_TO_PTR(self_in);
 mp_printf(print, "SoftI2C(scl=" MP_HAL_PIN_FMT ", sda=" MP_HAL_PIN_FMT ", freq=%u)",
 mp_hal_pin_name(self->scl), mp_hal_pin_name(self->sda), 500000 / self->us_delay);
}

STATIC void mp_machine_soft_i2c_init(mp_obj_base_t *self_in, size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
 enum { ARG_scl, ARG_sda, ARG_freq, ARG_timeout };
 static const mp_arg_t allowed_args[] = {
 { MP_QSTR_scl, MP_ARG_REQUIRED | MP_ARG_OBJ, {.u_obj = MP_OBJ_NULL} },
 { MP_QSTR_sda, MP_ARG_REQUIRED | MP_ARG_OBJ, {.u_obj = MP_OBJ_NULL} },
 { MP_QSTR_freq, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 400000} },
 { MP_QSTR_timeout, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 255} },
 };

 mp_machine_soft_i2c_obj_t *self = (mp_machine_soft_i2c_obj_t *)self_in;
 mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
 mp_arg_parse_all(n_args, pos_args, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);

 self->scl = mp_hal_get_pin_obj(args[ARG_scl].u_obj);
 self->sda = mp_hal_get_pin_obj(args[ARG_sda].u_obj);
 self->us_timeout = args[ARG_timeout].u_int;
 mp_hal_i2c_init(self, args[ARG_freq].u_int);
}

STATIC mp_obj_t mp_machine_soft_i2c_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *args) {
 // create new soft I2C object
 machine_i2c_obj_t *self = m_new_obj(machine_i2c_obj_t);
 self->base.type = &mp_machine_soft_i2c_type;
 mp_map_t kw_args;
 mp_map_init_fixed_table(&kw_args, n_kw, args + n_args);
 mp_machine_soft_i2c_init(&self->base, n_args, args, &kw_args);
 return MP_OBJ_FROM_PTR(self);
}

int mp_machine_soft_i2c_read(mp_obj_base_t *self_in, uint8_t *dest, size_t len, bool nack) {
 machine_i2c_obj_t *self = (machine_i2c_obj_t *)self_in;
 while (len--) {
 int ret = mp_hal_i2c_read_byte(self, dest++, nack && (len == 0));
 if (ret != 0) {
 return ret;
 }
 }
 return 0; // success
}

int mp_machine_soft_i2c_write(mp_obj_base_t *self_in, const uint8_t *src, size_t len) {
 machine_i2c_obj_t *self = (machine_i2c_obj_t *)self_in;
 int num_acks = 0;
 while (len--) {
 int ret = mp_hal_i2c_write_byte(self, *src++);
 if (ret < 0) {
 return ret;
 } else if (ret != 0) {
 // nack received, stop sending
 break;
 }
 ++num_acks;
 }
 return num_acks;
}

STATIC const mp_machine_i2c_p_t mp_machine_soft_i2c_p = {
 .init = mp_machine_soft_i2c_init,
 .start = (int (*)(mp_obj_base_t *))mp_hal_i2c_start,
 .stop = (int (*)(mp_obj_base_t *))mp_hal_i2c_stop,
 .read = mp_machine_soft_i2c_read,
 .write = mp_machine_soft_i2c_write,
 .transfer = mp_machine_soft_i2c_transfer,
};

const mp_obj_type_t mp_machine_soft_i2c_type = {
 { &mp_type_type },
 .name = MP_QSTR_SoftI2C,
 .print = mp_machine_soft_i2c_print,
 .make_new = mp_machine_soft_i2c_make_new,
 .protocol = &mp_machine_soft_i2c_p,
 .locals_dict = (mp_obj_dict_t *)&mp_machine_i2c_locals_dict,
};

#endif // MICROPY_PY_MACHINE_I2C