circuitpython/ports/stm32/i2c.c

/*
 * This file is part of the MicroPython project, http://micropython.org/
 *
 * The MIT License (MIT)
 *
 * Copyright (c) 2013, 2014 Damien P. George
 *
 * 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 <string.h>

#include "py/runtime.h"
#include "py/mphal.h"
#include "irq.h"
#include "pin.h"
#include "bufhelper.h"
#include "dma.h"
#include "i2c.h"

#if MICROPY_HW_ENABLE_HW_I2C

/// \moduleref pyb
/// \class I2C - a two-wire serial protocol
///
/// I2C is a two-wire protocol for communicating between devices.  At the physical
/// level it consists of 2 wires: SCL and SDA, the clock and data lines respectively.
///
/// I2C objects are created attached to a specific bus.  They can be initialised
/// when created, or initialised later on:
///
///     from pyb import I2C
///
///     i2c = I2C(1)                         # create on bus 1
///     i2c = I2C(1, I2C.MASTER)             # create and init as a master
///     i2c.init(I2C.MASTER, baudrate=20000) # init as a master
///     i2c.init(I2C.SLAVE, addr=0x42)       # init as a slave with given address
///     i2c.deinit()                         # turn off the peripheral
///
/// Printing the i2c object gives you information about its configuration.
///
/// Basic methods for slave are send and recv:
///
///     i2c.send('abc')      # send 3 bytes
///     i2c.send(0x42)       # send a single byte, given by the number
///     data = i2c.recv(3)   # receive 3 bytes
///
/// To receive inplace, first create a bytearray:
///
///     data = bytearray(3)  # create a buffer
///     i2c.recv(data)       # receive 3 bytes, writing them into data
///
/// You can specify a timeout (in ms):
///
///     i2c.send(b'123', timeout=2000)   # timout after 2 seconds
///
/// A master must specify the recipient's address:
///
///     i2c.init(I2C.MASTER)
///     i2c.send('123', 0x42)        # send 3 bytes to slave with address 0x42
///     i2c.send(b'456', addr=0x42)  # keyword for address
///
/// Master also has other methods:
///
///     i2c.is_ready(0x42)           # check if slave 0x42 is ready
///     i2c.scan()                   # scan for slaves on the bus, returning
///                                  #   a list of valid addresses
///     i2c.mem_read(3, 0x42, 2)     # read 3 bytes from memory of slave 0x42,
///                                  #   starting at address 2 in the slave
///     i2c.mem_write('abc', 0x42, 2, timeout=1000)
#define PYB_I2C_MASTER (0)
#define PYB_I2C_SLAVE  (1)

#define PYB_I2C_SPEED_STANDARD (100000L)
#define PYB_I2C_SPEED_FULL     (400000L)
#define PYB_I2C_SPEED_FAST     (1000000L)

#if defined(MICROPY_HW_I2C1_SCL)
I2C_HandleTypeDef I2CHandle1 = {.Instance = NULL};
#endif
#if defined(MICROPY_HW_I2C2_SCL)
I2C_HandleTypeDef I2CHandle2 = {.Instance = NULL};
#endif
#if defined(MICROPY_HW_I2C3_SCL)
I2C_HandleTypeDef I2CHandle3 = {.Instance = NULL};
#endif
#if defined(MICROPY_HW_I2C4_SCL)
I2C_HandleTypeDef I2CHandle4 = {.Instance = NULL};
#endif

STATIC bool pyb_i2c_use_dma[4];

const pyb_i2c_obj_t pyb_i2c_obj[] = {
    #if defined(MICROPY_HW_I2C1_SCL)
    {{&pyb_i2c_type}, &I2CHandle1, &dma_I2C_1_TX, &dma_I2C_1_RX, &pyb_i2c_use_dma[0]},
    #else
    {{&pyb_i2c_type}, NULL, NULL, NULL, NULL},
    #endif
    #if defined(MICROPY_HW_I2C2_SCL)
    {{&pyb_i2c_type}, &I2CHandle2, &dma_I2C_2_TX, &dma_I2C_2_RX, &pyb_i2c_use_dma[1]},
    #else
    {{&pyb_i2c_type}, NULL, NULL, NULL, NULL},
    #endif
    #if defined(MICROPY_HW_I2C3_SCL)
    {{&pyb_i2c_type}, &I2CHandle3, &dma_I2C_3_TX, &dma_I2C_3_RX, &pyb_i2c_use_dma[2]},
    #else
    {{&pyb_i2c_type}, NULL, NULL, NULL, NULL},
    #endif
    #if defined(MICROPY_HW_I2C4_SCL)
    {{&pyb_i2c_type}, &I2CHandle4, &dma_I2C_4_TX, &dma_I2C_4_RX, &pyb_i2c_use_dma[3]},
    #else
    {{&pyb_i2c_type}, NULL, NULL, NULL, NULL},
    #endif
};

#if defined(STM32F7) || defined(STM32L4) || defined(STM32H7)

// The STM32F0, F3, F7, H7 and L4 use a TIMINGR register rather than ClockSpeed and
// DutyCycle.

#if defined(STM32F746xx)

// The value 0x40912732 was obtained from the DISCOVERY_I2Cx_TIMING constant
// defined in the STM32F7Cube file Drivers/BSP/STM32F746G-Discovery/stm32f7456g_discovery.h
#define MICROPY_HW_I2C_BAUDRATE_TIMING { \
        {PYB_I2C_SPEED_STANDARD, 0x40912732}, \
        {PYB_I2C_SPEED_FULL, 0x10911823}, \
        {PYB_I2C_SPEED_FAST, 0x00611116}, \
    }
#define MICROPY_HW_I2C_BAUDRATE_DEFAULT (PYB_I2C_SPEED_FULL)
#define MICROPY_HW_I2C_BAUDRATE_MAX (PYB_I2C_SPEED_FAST)

#elif defined(STM32F722xx) || defined(STM32F723xx) \
    || defined(STM32F732xx) || defined(STM32F733xx) \
    || defined(STM32F767xx) || defined(STM32F769xx)

// These timing values are for f_I2CCLK=54MHz and are only approximate
#define MICROPY_HW_I2C_BAUDRATE_TIMING { \
        {PYB_I2C_SPEED_STANDARD, 0xb0420f13}, \
        {PYB_I2C_SPEED_FULL, 0x70330309}, \
        {PYB_I2C_SPEED_FAST, 0x50100103}, \
    }
#define MICROPY_HW_I2C_BAUDRATE_DEFAULT (PYB_I2C_SPEED_FULL)
#define MICROPY_HW_I2C_BAUDRATE_MAX (PYB_I2C_SPEED_FAST)

#elif defined(STM32H7)

// I2C TIMINGs obtained from the STHAL examples.
#define MICROPY_HW_I2C_BAUDRATE_TIMING { \
        {PYB_I2C_SPEED_STANDARD, 0x40604E73}, \
        {PYB_I2C_SPEED_FULL, 0x00901954}, \
        {PYB_I2C_SPEED_FAST, 0x10810915}, \
    }
#define MICROPY_HW_I2C_BAUDRATE_DEFAULT (PYB_I2C_SPEED_FULL)
#define MICROPY_HW_I2C_BAUDRATE_MAX (PYB_I2C_SPEED_FAST)

#elif defined(STM32L4)

// The value 0x90112626 was obtained from the DISCOVERY_I2C1_TIMING constant
// defined in the STM32L4Cube file Drivers/BSP/STM32L476G-Discovery/stm32l476g_discovery.h
#define MICROPY_HW_I2C_BAUDRATE_TIMING {{PYB_I2C_SPEED_STANDARD, 0x90112626}}
#define MICROPY_HW_I2C_BAUDRATE_DEFAULT (PYB_I2C_SPEED_STANDARD)
#define MICROPY_HW_I2C_BAUDRATE_MAX (PYB_I2C_SPEED_STANDARD)

#else
#error "no I2C timings for this MCU"
#endif

STATIC const struct {
    uint32_t    baudrate;
    uint32_t    timing;
} pyb_i2c_baudrate_timing[] = MICROPY_HW_I2C_BAUDRATE_TIMING;

#define NUM_BAUDRATE_TIMINGS MP_ARRAY_SIZE(pyb_i2c_baudrate_timing)

STATIC void i2c_set_baudrate(I2C_InitTypeDef *init, uint32_t baudrate) {
    for (int i = 0; i < NUM_BAUDRATE_TIMINGS; i++) {
        if (pyb_i2c_baudrate_timing[i].baudrate == baudrate) {
            init->Timing = pyb_i2c_baudrate_timing[i].timing;
            return;
        }
    }
    nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_ValueError,
                                            "Unsupported I2C baudrate: %lu", baudrate));
}

uint32_t i2c_get_baudrate(I2C_HandleTypeDef *i2c) {
    for (int i = 0; i < NUM_BAUDRATE_TIMINGS; i++) {
        if (pyb_i2c_baudrate_timing[i].timing == i2c->Init.Timing) {
            return pyb_i2c_baudrate_timing[i].baudrate;
        }
    }
    return 0;
}

#else

#define MICROPY_HW_I2C_BAUDRATE_DEFAULT (PYB_I2C_SPEED_FULL)
#define MICROPY_HW_I2C_BAUDRATE_MAX (PYB_I2C_SPEED_FULL)

STATIC void i2c_set_baudrate(I2C_InitTypeDef *init, uint32_t baudrate) {
    init->ClockSpeed = baudrate;
    init->DutyCycle = I2C_DUTYCYCLE_16_9;
}

uint32_t i2c_get_baudrate(I2C_HandleTypeDef *i2c) {
    uint32_t pfreq = i2c->Instance->CR2 & 0x3f;
    uint32_t ccr = i2c->Instance->CCR & 0xfff;
    if (i2c->Instance->CCR & 0x8000) {
        // Fast mode, assume duty cycle of 16/9
        return pfreq * 40000 / ccr;
    } else {
        // Standard mode
        return pfreq * 500000 / ccr;
    }
}

#endif

void i2c_init0(void) {
    // Initialise the I2C handles.
    // The structs live on the BSS so all other fields will be zero after a reset.
    #if defined(MICROPY_HW_I2C1_SCL)
    I2CHandle1.Instance = I2C1;
    #endif
    #if defined(MICROPY_HW_I2C2_SCL)
    I2CHandle2.Instance = I2C2;
    #endif
    #if defined(MICROPY_HW_I2C3_SCL)
    I2CHandle3.Instance = I2C3;
    #endif
    #if defined(MICROPY_HW_I2C4_SCL)
    I2CHandle4.Instance = I2C4;
    #endif
}

void i2c_init(I2C_HandleTypeDef *i2c) {
    int i2c_unit;
    const pin_obj_t *scl_pin;
    const pin_obj_t *sda_pin;

    if (0) {
    #if defined(MICROPY_HW_I2C1_SCL)
    } else if (i2c == &I2CHandle1) {
        i2c_unit = 1;
        scl_pin = MICROPY_HW_I2C1_SCL;
        sda_pin = MICROPY_HW_I2C1_SDA;
        __I2C1_CLK_ENABLE();
    #endif
    #if defined(MICROPY_HW_I2C2_SCL)
    } else if (i2c == &I2CHandle2) {
        i2c_unit = 2;
        scl_pin = MICROPY_HW_I2C2_SCL;
        sda_pin = MICROPY_HW_I2C2_SDA;
        __I2C2_CLK_ENABLE();
    #endif
    #if defined(MICROPY_HW_I2C3_SCL)
    } else if (i2c == &I2CHandle3) {
        i2c_unit = 3;
        scl_pin = MICROPY_HW_I2C3_SCL;
        sda_pin = MICROPY_HW_I2C3_SDA;
        __I2C3_CLK_ENABLE();
    #endif
    #if defined(MICROPY_HW_I2C4_SCL)
    } else if (i2c == &I2CHandle4) {
        i2c_unit = 4;
        scl_pin = MICROPY_HW_I2C4_SCL;
        sda_pin = MICROPY_HW_I2C4_SDA;
        __I2C4_CLK_ENABLE();
    #endif
    } else {
        // I2C does not exist for this board (shouldn't get here, should be checked by caller)
        return;
    }

    // init the GPIO lines
    uint32_t mode = MP_HAL_PIN_MODE_ALT_OPEN_DRAIN;
    uint32_t pull = MP_HAL_PIN_PULL_NONE; // have external pull-up resistors on both lines
    mp_hal_pin_config_alt(scl_pin, mode, pull, AF_FN_I2C, i2c_unit);
    mp_hal_pin_config_alt(sda_pin, mode, pull, AF_FN_I2C, i2c_unit);

    // init the I2C device
    if (HAL_I2C_Init(i2c) != HAL_OK) {
        // init error
        // TODO should raise an exception, but this function is not necessarily going to be
        // called via Python, so may not be properly wrapped in an NLR handler
        printf("OSError: HAL_I2C_Init failed\n");
        return;
    }

    // invalidate the DMA channels so they are initialised on first use
    const pyb_i2c_obj_t *self = &pyb_i2c_obj[i2c_unit - 1];
    dma_invalidate_channel(self->tx_dma_descr);
    dma_invalidate_channel(self->rx_dma_descr);

    if (0) {
    #if defined(MICROPY_HW_I2C1_SCL)
    } else if (i2c->Instance == I2C1) {
        HAL_NVIC_EnableIRQ(I2C1_EV_IRQn);
        HAL_NVIC_EnableIRQ(I2C1_ER_IRQn);
    #endif
    #if defined(MICROPY_HW_I2C2_SCL)
    } else if (i2c->Instance == I2C2) {
        HAL_NVIC_EnableIRQ(I2C2_EV_IRQn);
        HAL_NVIC_EnableIRQ(I2C2_ER_IRQn);
    #endif
    #if defined(MICROPY_HW_I2C3_SCL)
    } else if (i2c->Instance == I2C3) {
        HAL_NVIC_EnableIRQ(I2C3_EV_IRQn);
        HAL_NVIC_EnableIRQ(I2C3_ER_IRQn);
    #endif
    #if defined(MICROPY_HW_I2C4_SCL)
    } else if (i2c->Instance == I2C4) {
        HAL_NVIC_EnableIRQ(I2C4_EV_IRQn);
        HAL_NVIC_EnableIRQ(I2C4_ER_IRQn);
    #endif
    }
}

void i2c_deinit(I2C_HandleTypeDef *i2c) {
    HAL_I2C_DeInit(i2c);
    if (0) {
    #if defined(MICROPY_HW_I2C1_SCL)
    } else if (i2c->Instance == I2C1) {
        __I2C1_FORCE_RESET();
        __I2C1_RELEASE_RESET();
        __I2C1_CLK_DISABLE();
        HAL_NVIC_DisableIRQ(I2C1_EV_IRQn);
        HAL_NVIC_DisableIRQ(I2C1_ER_IRQn);
    #endif
    #if defined(MICROPY_HW_I2C2_SCL)
    } else if (i2c->Instance == I2C2) {
        __I2C2_FORCE_RESET();
        __I2C2_RELEASE_RESET();
        __I2C2_CLK_DISABLE();
        HAL_NVIC_DisableIRQ(I2C2_EV_IRQn);
        HAL_NVIC_DisableIRQ(I2C2_ER_IRQn);
    #endif
    #if defined(MICROPY_HW_I2C3_SCL)
    } else if (i2c->Instance == I2C3) {
        __I2C3_FORCE_RESET();
        __I2C3_RELEASE_RESET();
        __I2C3_CLK_DISABLE();
        HAL_NVIC_DisableIRQ(I2C3_EV_IRQn);
        HAL_NVIC_DisableIRQ(I2C3_ER_IRQn);
    #endif
    #if defined(MICROPY_HW_I2C4_SCL)
    } else if (i2c->Instance == I2C4) {
        __HAL_RCC_I2C4_FORCE_RESET();
        __HAL_RCC_I2C4_RELEASE_RESET();
        __HAL_RCC_I2C4_CLK_DISABLE();
        HAL_NVIC_DisableIRQ(I2C4_EV_IRQn);
        HAL_NVIC_DisableIRQ(I2C4_ER_IRQn);
    #endif
    }
}

void i2c_init_freq(const pyb_i2c_obj_t *self, mp_int_t freq) {
    I2C_InitTypeDef *init = &self->i2c->Init;

    init->AddressingMode    = I2C_ADDRESSINGMODE_7BIT;
    init->DualAddressMode   = I2C_DUALADDRESS_DISABLED;
    init->GeneralCallMode   = I2C_GENERALCALL_DISABLED;
    init->NoStretchMode     = I2C_NOSTRETCH_DISABLE;
    init->OwnAddress1       = PYB_I2C_MASTER_ADDRESS;
    init->OwnAddress2       = 0; // unused
    if (freq != -1) {
        i2c_set_baudrate(init, MIN(freq, MICROPY_HW_I2C_BAUDRATE_MAX));
    }

    *self->use_dma = false;

    // init the I2C bus
    i2c_deinit(self->i2c);
    i2c_init(self->i2c);
}

STATIC void i2c_reset_after_error(I2C_HandleTypeDef *i2c) {
    // wait for bus-busy flag to be cleared, with a timeout
    for (int timeout = 50; timeout > 0; --timeout) {
        if (!__HAL_I2C_GET_FLAG(i2c, I2C_FLAG_BUSY)) {
            // stop bit was generated and bus is back to normal
            return;
        }
        mp_hal_delay_ms(1);
    }
    // bus was/is busy, need to reset the peripheral to get it to work again
    i2c_deinit(i2c);
    i2c_init(i2c);
}

void i2c_ev_irq_handler(mp_uint_t i2c_id) {
    I2C_HandleTypeDef *hi2c;

    switch (i2c_id) {
        #if defined(MICROPY_HW_I2C1_SCL)
        case 1:
            hi2c = &I2CHandle1;
            break;
        #endif
        #if defined(MICROPY_HW_I2C2_SCL)
        case 2:
            hi2c = &I2CHandle2;
            break;
        #endif
        #if defined(MICROPY_HW_I2C3_SCL)
        case 3:
            hi2c = &I2CHandle3;
            break;
        #endif
        #if defined(MICROPY_HW_I2C4_SCL)
        case 4:
            hi2c = &I2CHandle4;
            break;
        #endif
        default:
            return;
    }

    #if defined(STM32F4)

    if (hi2c->Instance->SR1 & I2C_FLAG_BTF && hi2c->State == HAL_I2C_STATE_BUSY_TX) {
        if (hi2c->XferCount != 0U) {
            hi2c->Instance->DR = *hi2c->pBuffPtr++;
            hi2c->XferCount--;
        } else {
            __HAL_I2C_DISABLE_IT(hi2c, I2C_IT_EVT | I2C_IT_BUF | I2C_IT_ERR);
            if (hi2c->XferOptions != I2C_FIRST_FRAME) {
                hi2c->Instance->CR1 |= I2C_CR1_STOP;
            }
            hi2c->Mode = HAL_I2C_MODE_NONE;
            hi2c->State = HAL_I2C_STATE_READY;
        }
    }

    #else

    // if not an F4 MCU, use the HAL's IRQ handler
    HAL_I2C_EV_IRQHandler(hi2c);

    #endif
}

void i2c_er_irq_handler(mp_uint_t i2c_id) {
    I2C_HandleTypeDef *hi2c;

    switch (i2c_id) {
        #if defined(MICROPY_HW_I2C1_SCL)
        case 1:
            hi2c = &I2CHandle1;
            break;
        #endif
        #if defined(MICROPY_HW_I2C2_SCL)
        case 2:
            hi2c = &I2CHandle2;
            break;
        #endif
        #if defined(MICROPY_HW_I2C3_SCL)
        case 3:
            hi2c = &I2CHandle3;
            break;
        #endif
        #if defined(MICROPY_HW_I2C4_SCL)
        case 4:
            hi2c = &I2CHandle4;
            break;
        #endif
        default:
            return;
    }

    #if defined(STM32F4)

    uint32_t sr1 = hi2c->Instance->SR1;

    // I2C Bus error
    if (sr1 & I2C_FLAG_BERR) {
        hi2c->ErrorCode |= HAL_I2C_ERROR_BERR;
        __HAL_I2C_CLEAR_FLAG(hi2c, I2C_FLAG_BERR);
    }

    // I2C Arbitration Loss error
    if (sr1 & I2C_FLAG_ARLO) {
        hi2c->ErrorCode |= HAL_I2C_ERROR_ARLO;
        __HAL_I2C_CLEAR_FLAG(hi2c, I2C_FLAG_ARLO);
    }

    // I2C Acknowledge failure
    if (sr1 & I2C_FLAG_AF) {
        hi2c->ErrorCode |= HAL_I2C_ERROR_AF;
        SET_BIT(hi2c->Instance->CR1,I2C_CR1_STOP);
        __HAL_I2C_CLEAR_FLAG(hi2c, I2C_FLAG_AF);
    }

    // I2C Over-Run/Under-Run
    if (sr1 & I2C_FLAG_OVR) {
        hi2c->ErrorCode |= HAL_I2C_ERROR_OVR;
        __HAL_I2C_CLEAR_FLAG(hi2c, I2C_FLAG_OVR);
    }

    #else

    // if not an F4 MCU, use the HAL's IRQ handler
    HAL_I2C_ER_IRQHandler(hi2c);

    #endif
}

STATIC HAL_StatusTypeDef i2c_wait_dma_finished(I2C_HandleTypeDef *i2c, uint32_t timeout) {
    // Note: we can't use WFI to idle in this loop because the DMA completion
    // interrupt may occur before the WFI.  Hence we miss it and have to wait
    // until the next sys-tick (up to 1ms).
    uint32_t start = HAL_GetTick();
    while (HAL_I2C_GetState(i2c) != HAL_I2C_STATE_READY) {
        if (HAL_GetTick() - start >= timeout) {
            return HAL_TIMEOUT;
        }
    }
    return HAL_OK;
}

/******************************************************************************/
/* MicroPython bindings                                                       */

static inline bool in_master_mode(pyb_i2c_obj_t *self) { return self->i2c->Init.OwnAddress1 == PYB_I2C_MASTER_ADDRESS; }

STATIC void pyb_i2c_print(const mp_print_t *print, mp_obj_t self_in, mp_print_kind_t kind) {
    pyb_i2c_obj_t *self = self_in;

    uint i2c_num = 0;
    if (0) { }
    #if defined(MICROPY_HW_I2C1_SCL)
    else if (self->i2c->Instance == I2C1) { i2c_num = 1; }
    #endif
    #if defined(MICROPY_HW_I2C2_SCL)
    else if (self->i2c->Instance == I2C2) { i2c_num = 2; }
    #endif
    #if defined(MICROPY_HW_I2C3_SCL)
    else if (self->i2c->Instance == I2C3) { i2c_num = 3; }
    #endif
    #if defined(MICROPY_HW_I2C4_SCL)
    else if (self->i2c->Instance == I2C4) { i2c_num = 4; }
    #endif

    if (self->i2c->State == HAL_I2C_STATE_RESET) {
        mp_printf(print, "I2C(%u)", i2c_num);
    } else {
        if (in_master_mode(self)) {
            mp_printf(print, "I2C(%u, I2C.MASTER, baudrate=%u)", i2c_num, i2c_get_baudrate(self->i2c));
        } else {
            mp_printf(print, "I2C(%u, I2C.SLAVE, addr=0x%02x)", i2c_num, (self->i2c->Instance->OAR1 >> 1) & 0x7f);
        }
    }
}

/// \method init(mode, *, addr=0x12, baudrate=400000, gencall=False)
///
/// Initialise the I2C bus with the given parameters:
///
///   - `mode` must be either `I2C.MASTER` or `I2C.SLAVE`
///   - `addr` is the 7-bit address (only sensible for a slave)
///   - `baudrate` is the SCL clock rate (only sensible for a master)
///   - `gencall` is whether to support general call mode
STATIC mp_obj_t pyb_i2c_init_helper(const pyb_i2c_obj_t *self, size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
    static const mp_arg_t allowed_args[] = {
        { MP_QSTR_mode,     MP_ARG_INT, {.u_int = PYB_I2C_MASTER} },
        { MP_QSTR_addr,     MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 0x12} },
        { MP_QSTR_baudrate, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = MICROPY_HW_I2C_BAUDRATE_DEFAULT} },
        { MP_QSTR_gencall,  MP_ARG_KW_ONLY | MP_ARG_BOOL, {.u_bool = false} },
        { MP_QSTR_dma,      MP_ARG_KW_ONLY | MP_ARG_BOOL, {.u_bool = false} },
    };

    // parse args
    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);

    // set the I2C configuration values
    I2C_InitTypeDef *init = &self->i2c->Init;

    if (args[0].u_int == PYB_I2C_MASTER) {
        // use a special address to indicate we are a master
        init->OwnAddress1 = PYB_I2C_MASTER_ADDRESS;
    } else {
        init->OwnAddress1 = (args[1].u_int << 1) & 0xfe;
    }

    i2c_set_baudrate(init, MIN(args[2].u_int, MICROPY_HW_I2C_BAUDRATE_MAX));
    init->AddressingMode  = I2C_ADDRESSINGMODE_7BIT;
    init->DualAddressMode = I2C_DUALADDRESS_DISABLED;
    init->GeneralCallMode = args[3].u_bool ? I2C_GENERALCALL_ENABLED : I2C_GENERALCALL_DISABLED;
    init->OwnAddress2     = 0; // unused
    init->NoStretchMode   = I2C_NOSTRETCH_DISABLE;

    *self->use_dma = args[4].u_bool;

    // init the I2C bus
    i2c_deinit(self->i2c);
    i2c_init(self->i2c);

    return mp_const_none;
}

/// \classmethod \constructor(bus, ...)
///
/// Construct an I2C object on the given bus.  `bus` can be 1 or 2.
/// With no additional parameters, the I2C object is created but not
/// initialised (it has the settings from the last initialisation of
/// the bus, if any).  If extra arguments are given, the bus is initialised.
/// See `init` for parameters of initialisation.
///
/// The physical pins of the I2C busses are:
///
///   - `I2C(1)` is on the X position: `(SCL, SDA) = (X9, X10) = (PB6, PB7)`
///   - `I2C(2)` is on the Y position: `(SCL, SDA) = (Y9, Y10) = (PB10, PB11)`
STATIC mp_obj_t pyb_i2c_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *args) {
    // check arguments
    mp_arg_check_num(n_args, n_kw, 1, MP_OBJ_FUN_ARGS_MAX, true);

    // work out i2c bus
    int i2c_id = 0;
    if (MP_OBJ_IS_STR(args[0])) {
        const char *port = mp_obj_str_get_str(args[0]);
        if (0) {
        #ifdef MICROPY_HW_I2C1_NAME
        } else if (strcmp(port, MICROPY_HW_I2C1_NAME) == 0) {
            i2c_id = 1;
        #endif
        #ifdef MICROPY_HW_I2C2_NAME
        } else if (strcmp(port, MICROPY_HW_I2C2_NAME) == 0) {
            i2c_id = 2;
        #endif
        #ifdef MICROPY_HW_I2C3_NAME
        } else if (strcmp(port, MICROPY_HW_I2C3_NAME) == 0) {
            i2c_id = 3;
        #endif
        } else {
            nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_ValueError,
                "I2C(%s) doesn't exist", port));
        }
    } else {
        i2c_id = mp_obj_get_int(args[0]);
        if (i2c_id < 1 || i2c_id > MP_ARRAY_SIZE(pyb_i2c_obj)
            || pyb_i2c_obj[i2c_id - 1].i2c == NULL) {
            nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_ValueError,
                "I2C(%d) doesn't exist", i2c_id));
        }
    }

    // get I2C object
    const pyb_i2c_obj_t *i2c_obj = &pyb_i2c_obj[i2c_id - 1];

    if (n_args > 1 || n_kw > 0) {
        // start the peripheral
        mp_map_t kw_args;
        mp_map_init_fixed_table(&kw_args, n_kw, args + n_args);
        pyb_i2c_init_helper(i2c_obj, n_args - 1, args + 1, &kw_args);
    }

    return (mp_obj_t)i2c_obj;
}

STATIC mp_obj_t pyb_i2c_init(size_t n_args, const mp_obj_t *args, mp_map_t *kw_args) {
    return pyb_i2c_init_helper(args[0], n_args - 1, args + 1, kw_args);
}
STATIC MP_DEFINE_CONST_FUN_OBJ_KW(pyb_i2c_init_obj, 1, pyb_i2c_init);

/// \method deinit()
/// Turn off the I2C bus.
STATIC mp_obj_t pyb_i2c_deinit(mp_obj_t self_in) {
    pyb_i2c_obj_t *self = self_in;
    i2c_deinit(self->i2c);
    return mp_const_none;
}
STATIC MP_DEFINE_CONST_FUN_OBJ_1(pyb_i2c_deinit_obj, pyb_i2c_deinit);

/// \method is_ready(addr)
/// Check if an I2C device responds to the given address.  Only valid when in master mode.
STATIC mp_obj_t pyb_i2c_is_ready(mp_obj_t self_in, mp_obj_t i2c_addr_o) {
    pyb_i2c_obj_t *self = self_in;

    if (!in_master_mode(self)) {
        mp_raise_TypeError("I2C must be a master");
    }

    mp_uint_t i2c_addr = mp_obj_get_int(i2c_addr_o) << 1;

    for (int i = 0; i < 10; i++) {
        HAL_StatusTypeDef status = HAL_I2C_IsDeviceReady(self->i2c, i2c_addr, 10, 200);
        if (status == HAL_OK) {
            return mp_const_true;
        }
    }

    return mp_const_false;
}
STATIC MP_DEFINE_CONST_FUN_OBJ_2(pyb_i2c_is_ready_obj, pyb_i2c_is_ready);

/// \method scan()
/// Scan all I2C addresses from 0x08 to 0x77 and return a list of those that respond.
/// Only valid when in master mode.
STATIC mp_obj_t pyb_i2c_scan(mp_obj_t self_in) {
    pyb_i2c_obj_t *self = self_in;

    if (!in_master_mode(self)) {
        mp_raise_TypeError("I2C must be a master");
    }

    mp_obj_t list = mp_obj_new_list(0, NULL);

    for (uint addr = 0x08; addr <= 0x77; addr++) {
        HAL_StatusTypeDef status = HAL_I2C_IsDeviceReady(self->i2c, addr << 1, 1, 200);
        if (status == HAL_OK) {
            mp_obj_list_append(list, MP_OBJ_NEW_SMALL_INT(addr));
        }
    }

    return list;
}
STATIC MP_DEFINE_CONST_FUN_OBJ_1(pyb_i2c_scan_obj, pyb_i2c_scan);

/// \method send(send, addr=0x00, timeout=5000)
/// Send data on the bus:
///
///   - `send` is the data to send (an integer to send, or a buffer object)
///   - `addr` is the address to send to (only required in master mode)
///   - `timeout` is the timeout in milliseconds to wait for the send
///
/// Return value: `None`.
STATIC mp_obj_t pyb_i2c_send(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
    static const mp_arg_t allowed_args[] = {
        { MP_QSTR_send,    MP_ARG_REQUIRED | MP_ARG_OBJ, {.u_obj = MP_OBJ_NULL} },
        { MP_QSTR_addr,    MP_ARG_INT, {.u_int = PYB_I2C_MASTER_ADDRESS} },
        { MP_QSTR_timeout, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 5000} },
    };

    // parse args
    pyb_i2c_obj_t *self = pos_args[0];
    mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
    mp_arg_parse_all(n_args - 1, pos_args + 1, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);

    // get the buffer to send from
    mp_buffer_info_t bufinfo;
    uint8_t data[1];
    pyb_buf_get_for_send(args[0].u_obj, &bufinfo, data);

    // if option is set and IRQs are enabled then we can use DMA
    bool use_dma = *self->use_dma && query_irq() == IRQ_STATE_ENABLED;

    DMA_HandleTypeDef tx_dma;
    if (use_dma) {
        dma_init(&tx_dma, self->tx_dma_descr, self->i2c);
        self->i2c->hdmatx = &tx_dma;
        self->i2c->hdmarx = NULL;
    }

    // send the data
    HAL_StatusTypeDef status;
    if (in_master_mode(self)) {
        if (args[1].u_int == PYB_I2C_MASTER_ADDRESS) {
            if (use_dma) {
                dma_deinit(self->tx_dma_descr);
            }
            mp_raise_TypeError("addr argument required");
        }
        mp_uint_t i2c_addr = args[1].u_int << 1;
        if (!use_dma) {
            status = HAL_I2C_Master_Transmit(self->i2c, i2c_addr, bufinfo.buf, bufinfo.len, args[2].u_int);
        } else {
            MP_HAL_CLEAN_DCACHE(bufinfo.buf, bufinfo.len);
            status = HAL_I2C_Master_Transmit_DMA(self->i2c, i2c_addr, bufinfo.buf, bufinfo.len);
        }
    } else {
        if (!use_dma) {
            status = HAL_I2C_Slave_Transmit(self->i2c, bufinfo.buf, bufinfo.len, args[2].u_int);
        } else {
            MP_HAL_CLEAN_DCACHE(bufinfo.buf, bufinfo.len);
            status = HAL_I2C_Slave_Transmit_DMA(self->i2c, bufinfo.buf, bufinfo.len);
        }
    }

    // if we used DMA, wait for it to finish
    if (use_dma) {
        if (status == HAL_OK) {
            status = i2c_wait_dma_finished(self->i2c, args[2].u_int);
        }
        dma_deinit(self->tx_dma_descr);
    }

    if (status != HAL_OK) {
        i2c_reset_after_error(self->i2c);
        mp_hal_raise(status);
    }

    return mp_const_none;
}
STATIC MP_DEFINE_CONST_FUN_OBJ_KW(pyb_i2c_send_obj, 1, pyb_i2c_send);

/// \method recv(recv, addr=0x00, timeout=5000)
///
/// Receive data on the bus:
///
///   - `recv` can be an integer, which is the number of bytes to receive,
///     or a mutable buffer, which will be filled with received bytes
///   - `addr` is the address to receive from (only required in master mode)
///   - `timeout` is the timeout in milliseconds to wait for the receive
///
/// Return value: if `recv` is an integer then a new buffer of the bytes received,
/// otherwise the same buffer that was passed in to `recv`.
STATIC mp_obj_t pyb_i2c_recv(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
    static const mp_arg_t allowed_args[] = {
        { MP_QSTR_recv,    MP_ARG_REQUIRED | MP_ARG_OBJ, {.u_obj = MP_OBJ_NULL} },
        { MP_QSTR_addr,    MP_ARG_INT, {.u_int = PYB_I2C_MASTER_ADDRESS} },
        { MP_QSTR_timeout, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 5000} },
    };

    // parse args
    pyb_i2c_obj_t *self = pos_args[0];
    mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
    mp_arg_parse_all(n_args - 1, pos_args + 1, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);

    // get the buffer to receive into
    vstr_t vstr;
    mp_obj_t o_ret = pyb_buf_get_for_recv(args[0].u_obj, &vstr);

    // if option is set and IRQs are enabled then we can use DMA
    bool use_dma = *self->use_dma && query_irq() == IRQ_STATE_ENABLED;

    DMA_HandleTypeDef rx_dma;
    if (use_dma) {
        dma_init(&rx_dma, self->rx_dma_descr, self->i2c);
        self->i2c->hdmatx = NULL;
        self->i2c->hdmarx = &rx_dma;
    }

    // receive the data
    HAL_StatusTypeDef status;
    if (in_master_mode(self)) {
        if (args[1].u_int == PYB_I2C_MASTER_ADDRESS) {
            mp_raise_TypeError("addr argument required");
        }
        mp_uint_t i2c_addr = args[1].u_int << 1;
        if (!use_dma) {
            status = HAL_I2C_Master_Receive(self->i2c, i2c_addr, (uint8_t*)vstr.buf, vstr.len, args[2].u_int);
        } else {
            MP_HAL_CLEANINVALIDATE_DCACHE(vstr.buf, vstr.len);
            status = HAL_I2C_Master_Receive_DMA(self->i2c, i2c_addr, (uint8_t*)vstr.buf, vstr.len);
        }
    } else {
        if (!use_dma) {
            status = HAL_I2C_Slave_Receive(self->i2c, (uint8_t*)vstr.buf, vstr.len, args[2].u_int);
        } else {
            MP_HAL_CLEANINVALIDATE_DCACHE(vstr.buf, vstr.len);
            status = HAL_I2C_Slave_Receive_DMA(self->i2c, (uint8_t*)vstr.buf, vstr.len);
        }
    }

    // if we used DMA, wait for it to finish
    if (use_dma) {
        if (status == HAL_OK) {
            status = i2c_wait_dma_finished(self->i2c, args[2].u_int);
        }
        dma_deinit(self->rx_dma_descr);
    }

    if (status != HAL_OK) {
        i2c_reset_after_error(self->i2c);
        mp_hal_raise(status);
    }

    // return the received data
    if (o_ret != MP_OBJ_NULL) {
        return o_ret;
    } else {
        return mp_obj_new_str_from_vstr(&mp_type_bytes, &vstr);
    }
}
STATIC MP_DEFINE_CONST_FUN_OBJ_KW(pyb_i2c_recv_obj, 1, pyb_i2c_recv);

/// \method mem_read(data, addr, memaddr, timeout=5000, addr_size=8)
///
/// Read from the memory of an I2C device:
///
///   - `data` can be an integer or a buffer to read into
///   - `addr` is the I2C device address
///   - `memaddr` is the memory location within the I2C device
///   - `timeout` is the timeout in milliseconds to wait for the read
///   - `addr_size` selects width of memaddr: 8 or 16 bits
///
/// Returns the read data.
/// This is only valid in master mode.
STATIC const mp_arg_t pyb_i2c_mem_read_allowed_args[] = {
    { MP_QSTR_data,    MP_ARG_REQUIRED | MP_ARG_OBJ, {.u_obj = MP_OBJ_NULL} },
    { 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_timeout, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 5000} },
    { MP_QSTR_addr_size, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 8} },
};

STATIC mp_obj_t pyb_i2c_mem_read(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
    // parse args
    pyb_i2c_obj_t *self = pos_args[0];
    mp_arg_val_t args[MP_ARRAY_SIZE(pyb_i2c_mem_read_allowed_args)];
    mp_arg_parse_all(n_args - 1, pos_args + 1, kw_args, MP_ARRAY_SIZE(pyb_i2c_mem_read_allowed_args), pyb_i2c_mem_read_allowed_args, args);

    if (!in_master_mode(self)) {
        mp_raise_TypeError("I2C must be a master");
    }

    // get the buffer to read into
    vstr_t vstr;
    mp_obj_t o_ret = pyb_buf_get_for_recv(args[0].u_obj, &vstr);

    // get the addresses
    mp_uint_t i2c_addr = args[1].u_int << 1;
    mp_uint_t mem_addr = args[2].u_int;
    // determine width of mem_addr; default is 8 bits, entering any other value gives 16 bit width
    mp_uint_t mem_addr_size = I2C_MEMADD_SIZE_8BIT;
    if (args[4].u_int != 8) {
        mem_addr_size = I2C_MEMADD_SIZE_16BIT;
    }

    // if option is set and IRQs are enabled then we can use DMA
    bool use_dma = *self->use_dma && query_irq() == IRQ_STATE_ENABLED;

    HAL_StatusTypeDef status;
    if (!use_dma) {
        status = HAL_I2C_Mem_Read(self->i2c, i2c_addr, mem_addr, mem_addr_size, (uint8_t*)vstr.buf, vstr.len, args[3].u_int);
    } else {
        DMA_HandleTypeDef rx_dma;
        dma_init(&rx_dma, self->rx_dma_descr, self->i2c);
        self->i2c->hdmatx = NULL;
        self->i2c->hdmarx = &rx_dma;
        MP_HAL_CLEANINVALIDATE_DCACHE(vstr.buf, vstr.len);
        status = HAL_I2C_Mem_Read_DMA(self->i2c, i2c_addr, mem_addr, mem_addr_size, (uint8_t*)vstr.buf, vstr.len);
        if (status == HAL_OK) {
            status = i2c_wait_dma_finished(self->i2c, args[3].u_int);
        }
        dma_deinit(self->rx_dma_descr);
    }

    if (status != HAL_OK) {
        i2c_reset_after_error(self->i2c);
        mp_hal_raise(status);
    }

    // return the read data
    if (o_ret != MP_OBJ_NULL) {
        return o_ret;
    } else {
        return mp_obj_new_str_from_vstr(&mp_type_bytes, &vstr);
    }
}
STATIC MP_DEFINE_CONST_FUN_OBJ_KW(pyb_i2c_mem_read_obj, 1, pyb_i2c_mem_read);

/// \method mem_write(data, addr, memaddr, timeout=5000, addr_size=8)
///
/// Write to the memory of an I2C device:
///
///   - `data` can be an integer or a buffer to write from
///   - `addr` is the I2C device address
///   - `memaddr` is the memory location within the I2C device
///   - `timeout` is the timeout in milliseconds to wait for the write
///   - `addr_size` selects width of memaddr: 8 or 16 bits
///
/// Returns `None`.
/// This is only valid in master mode.
STATIC mp_obj_t pyb_i2c_mem_write(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
    // parse args (same as mem_read)
    pyb_i2c_obj_t *self = pos_args[0];
    mp_arg_val_t args[MP_ARRAY_SIZE(pyb_i2c_mem_read_allowed_args)];
    mp_arg_parse_all(n_args - 1, pos_args + 1, kw_args, MP_ARRAY_SIZE(pyb_i2c_mem_read_allowed_args), pyb_i2c_mem_read_allowed_args, args);

    if (!in_master_mode(self)) {
        mp_raise_TypeError("I2C must be a master");
    }

    // get the buffer to write from
    mp_buffer_info_t bufinfo;
    uint8_t data[1];
    pyb_buf_get_for_send(args[0].u_obj, &bufinfo, data);

    // get the addresses
    mp_uint_t i2c_addr = args[1].u_int << 1;
    mp_uint_t mem_addr = args[2].u_int;
    // determine width of mem_addr; default is 8 bits, entering any other value gives 16 bit width
    mp_uint_t mem_addr_size = I2C_MEMADD_SIZE_8BIT;
    if (args[4].u_int != 8) {
        mem_addr_size = I2C_MEMADD_SIZE_16BIT;
    }

    // if option is set and IRQs are enabled then we can use DMA
    bool use_dma = *self->use_dma && query_irq() == IRQ_STATE_ENABLED;

    HAL_StatusTypeDef status;
    if (!use_dma) {
        status = HAL_I2C_Mem_Write(self->i2c, i2c_addr, mem_addr, mem_addr_size, bufinfo.buf, bufinfo.len, args[3].u_int);
    } else {
        DMA_HandleTypeDef tx_dma;
        dma_init(&tx_dma, self->tx_dma_descr, self->i2c);
        self->i2c->hdmatx = &tx_dma;
        self->i2c->hdmarx = NULL;
        MP_HAL_CLEAN_DCACHE(bufinfo.buf, bufinfo.len);
        status = HAL_I2C_Mem_Write_DMA(self->i2c, i2c_addr, mem_addr, mem_addr_size, bufinfo.buf, bufinfo.len);
        if (status == HAL_OK) {
            status = i2c_wait_dma_finished(self->i2c, args[3].u_int);
        }
        dma_deinit(self->tx_dma_descr);
    }

    if (status != HAL_OK) {
        i2c_reset_after_error(self->i2c);
        mp_hal_raise(status);
    }

    return mp_const_none;
}
STATIC MP_DEFINE_CONST_FUN_OBJ_KW(pyb_i2c_mem_write_obj, 1, pyb_i2c_mem_write);

STATIC const mp_rom_map_elem_t pyb_i2c_locals_dict_table[] = {
    // instance methods
    { MP_ROM_QSTR(MP_QSTR_init), MP_ROM_PTR(&pyb_i2c_init_obj) },
    { MP_ROM_QSTR(MP_QSTR_deinit), MP_ROM_PTR(&pyb_i2c_deinit_obj) },
    { MP_ROM_QSTR(MP_QSTR_is_ready), MP_ROM_PTR(&pyb_i2c_is_ready_obj) },
    { MP_ROM_QSTR(MP_QSTR_scan), MP_ROM_PTR(&pyb_i2c_scan_obj) },
    { MP_ROM_QSTR(MP_QSTR_send), MP_ROM_PTR(&pyb_i2c_send_obj) },
    { MP_ROM_QSTR(MP_QSTR_recv), MP_ROM_PTR(&pyb_i2c_recv_obj) },
    { MP_ROM_QSTR(MP_QSTR_mem_read), MP_ROM_PTR(&pyb_i2c_mem_read_obj) },
    { MP_ROM_QSTR(MP_QSTR_mem_write), MP_ROM_PTR(&pyb_i2c_mem_write_obj) },

    // class constants
    /// \constant MASTER - for initialising the bus to master mode
    /// \constant SLAVE - for initialising the bus to slave mode
    { MP_ROM_QSTR(MP_QSTR_MASTER), MP_ROM_INT(PYB_I2C_MASTER) },
    { MP_ROM_QSTR(MP_QSTR_SLAVE), MP_ROM_INT(PYB_I2C_SLAVE) },
};

STATIC MP_DEFINE_CONST_DICT(pyb_i2c_locals_dict, pyb_i2c_locals_dict_table);

const mp_obj_type_t pyb_i2c_type = {
    { &mp_type_type },
    .name = MP_QSTR_I2C,
    .print = pyb_i2c_print,
    .make_new = pyb_i2c_make_new,
    .locals_dict = (mp_obj_dict_t*)&pyb_i2c_locals_dict,
};

#endif // MICROPY_HW_ENABLE_HW_I2C