cc3200/mods/pybi2c.c - lite/micropython - Linaro Git Browser

 /*
  * This file is part of the Micro Python project, http://micropython.org/
  *
  * The MIT License (MIT)
  *
  * Copyright (c) 2013, 2014 Damien P. George
  * Copyright (c) 2015 Daniel Campora
  *
  * 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/mpstate.h"
 #include "py/runtime.h"
 #include "py/mphal.h"
 #include "bufhelper.h"
 #include "inc/hw_types.h"
 #include "inc/hw_i2c.h"
 #include "inc/hw_ints.h"
 #include "inc/hw_memmap.h"
 #include "rom_map.h"
 #include "pin.h"
 #include "prcm.h"
 #include "i2c.h"
 #include "pybi2c.h"
 #include "mpexception.h"
 #include "pybsleep.h"
 #include "utils.h"
 #include "pybpin.h"
 #include "pins.h"

 /// \moduleref pyb
 /// \class I2C - a two-wire serial protocol

 typedef struct _pyb_i2c_obj_t {
     mp_obj_base_t base;
     uint baudrate;
 } pyb_i2c_obj_t;

 /******************************************************************************
  DEFINE CONSTANTS
  ******************************************************************************/
 #define PYBI2C_MASTER                          (0)

 #define PYBI2C_MIN_BAUD_RATE_HZ                (50000)
 #define PYBI2C_MAX_BAUD_RATE_HZ                (400000)

 #define PYBI2C_TRANSC_TIMEOUT_MS               (10)
 #define PYBI2C_TRANSAC_WAIT_DELAY_US           (10)

 #define PYBI2C_TIMEOUT_TO_COUNT(to_us, baud)   (((baud) * to_us) / 16000000)

 #define RET_IF_ERR(Func)                        {                           \
                                                     if (!Func) {            \
                                                         return  false;      \
                                                     }                       \
                                                 }

 /******************************************************************************
  DECLARE PRIVATE DATA
  ******************************************************************************/
 STATIC pyb_i2c_obj_t pyb_i2c_obj = {.baudrate = 0};

 STATIC const mp_obj_t pyb_i2c_def_pin[2] = {&pin_GP13, &pin_GP23};

 /******************************************************************************
  DEFINE PRIVATE FUNCTIONS
  ******************************************************************************/
 // only master mode is available for the moment
 STATIC void i2c_init (pyb_i2c_obj_t *self) {
     // Enable the I2C Peripheral
     MAP_PRCMPeripheralClkEnable(PRCM_I2CA0, PRCM_RUN_MODE_CLK | PRCM_SLP_MODE_CLK);
     MAP_PRCMPeripheralReset(PRCM_I2CA0);
     // Configure I2C module with the specified baudrate
     MAP_I2CMasterInitExpClk(I2CA0_BASE, self->baudrate);
 }

 STATIC bool pyb_i2c_transaction(uint cmd) {
     // Convert the timeout to microseconds
     int32_t timeout = PYBI2C_TRANSC_TIMEOUT_MS * 1000;
     // Sanity check, t_timeout must be between 1 and 255
     uint t_timeout = MIN(PYBI2C_TIMEOUT_TO_COUNT(timeout, pyb_i2c_obj.baudrate), 255);
     // Clear all interrupts
     MAP_I2CMasterIntClearEx(I2CA0_BASE, MAP_I2CMasterIntStatusEx(I2CA0_BASE, false));
     // Set the time-out in terms of clock cycles. Not to be used with breakpoints.
     MAP_I2CMasterTimeoutSet(I2CA0_BASE, t_timeout);
     // Initiate the transfer.
     MAP_I2CMasterControl(I2CA0_BASE, cmd);
     // Wait until the current byte has been transferred.
     // Poll on the raw interrupt status.
     while ((MAP_I2CMasterIntStatusEx(I2CA0_BASE, false) & (I2C_MASTER_INT_DATA | I2C_MASTER_INT_TIMEOUT)) == 0) {
         // wait for a few microseconds
         UtilsDelay(UTILS_DELAY_US_TO_COUNT(PYBI2C_TRANSAC_WAIT_DELAY_US));
         timeout -= PYBI2C_TRANSAC_WAIT_DELAY_US;
         if (timeout < 0) {
             // the peripheral is not responding, so stop
             return false;
         }
     }

     // Check for any errors in the transfer
     if (MAP_I2CMasterErr(I2CA0_BASE) != I2C_MASTER_ERR_NONE) {
         switch(cmd) {
         case I2C_MASTER_CMD_BURST_SEND_START:
         case I2C_MASTER_CMD_BURST_SEND_CONT:
         case I2C_MASTER_CMD_BURST_SEND_STOP:
             MAP_I2CMasterControl(I2CA0_BASE, I2C_MASTER_CMD_BURST_SEND_ERROR_STOP);
             break;
         case I2C_MASTER_CMD_BURST_RECEIVE_START:
         case I2C_MASTER_CMD_BURST_RECEIVE_CONT:
         case I2C_MASTER_CMD_BURST_RECEIVE_FINISH:
             MAP_I2CMasterControl(I2CA0_BASE, I2C_MASTER_CMD_BURST_RECEIVE_ERROR_STOP);
             break;
         default:
             break;
         }
         return false;
     }
     return true;
 }

 STATIC void pyb_i2c_check_init(pyb_i2c_obj_t *self) {
     // not initialized
     if (!self->baudrate) {
         nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, mpexception_os_request_not_possible));
     }
 }

 STATIC bool pyb_i2c_scan_device(byte devAddr) {
     // Set I2C codec slave address
     MAP_I2CMasterSlaveAddrSet(I2CA0_BASE, devAddr, true);
     // Initiate the transfer.
     RET_IF_ERR(pyb_i2c_transaction(I2C_MASTER_CMD_SINGLE_RECEIVE));
     // Since this is a hack, send the stop bit anyway
     MAP_I2CMasterControl(I2CA0_BASE, I2C_MASTER_CMD_BURST_SEND_ERROR_STOP);
     return true;
 }

 STATIC bool pyb_i2c_mem_addr_write (byte addr, byte *mem_addr, uint mem_addr_len) {
     // Set I2C codec slave address
     MAP_I2CMasterSlaveAddrSet(I2CA0_BASE, addr, false);
     // Write the first byte to the controller.
     MAP_I2CMasterDataPut(I2CA0_BASE, *mem_addr++);
     // Initiate the transfer.
     RET_IF_ERR(pyb_i2c_transaction(I2C_MASTER_CMD_BURST_SEND_START));

     // Loop until the completion of transfer or error
     while (--mem_addr_len) {
         // Write the next byte of data
         MAP_I2CMasterDataPut(I2CA0_BASE, *mem_addr++);
         // Transact over I2C to send the next byte
         RET_IF_ERR(pyb_i2c_transaction(I2C_MASTER_CMD_BURST_SEND_CONT));
     }
     return true;
 }

 STATIC bool pyb_i2c_mem_write (byte addr, byte *mem_addr, uint mem_addr_len, byte *data, uint data_len) {
     if (pyb_i2c_mem_addr_write (addr, mem_addr, mem_addr_len)) {
         // Loop until the completion of transfer or error
         while (data_len--) {
             // Write the next byte of data
             MAP_I2CMasterDataPut(I2CA0_BASE, *data++);
             // Transact over I2C to send the byte
             RET_IF_ERR(pyb_i2c_transaction(I2C_MASTER_CMD_BURST_SEND_CONT));
         }
         // send the stop bit
         RET_IF_ERR(pyb_i2c_transaction(I2C_MASTER_CMD_BURST_SEND_STOP));
         return true;
     }
     return false;
 }

 STATIC bool pyb_i2c_write(byte addr, byte *data, uint len, bool stop) {
     // Set I2C codec slave address
     MAP_I2CMasterSlaveAddrSet(I2CA0_BASE, addr, false);
     // Write the first byte to the controller.
     MAP_I2CMasterDataPut(I2CA0_BASE, *data++);
     // Initiate the transfer.
     RET_IF_ERR(pyb_i2c_transaction(I2C_MASTER_CMD_BURST_SEND_START));

     // Loop until the completion of transfer or error
     while (--len) {
         // Write the next byte of data
         MAP_I2CMasterDataPut(I2CA0_BASE, *data++);
         // Transact over I2C to send the byte
         RET_IF_ERR(pyb_i2c_transaction(I2C_MASTER_CMD_BURST_SEND_CONT));
     }

     // If a stop bit is to be sent, do it.
     if (stop) {
         RET_IF_ERR(pyb_i2c_transaction(I2C_MASTER_CMD_BURST_SEND_STOP));
     }
     return true;
 }

 STATIC bool pyb_i2c_read(byte addr, byte *data, uint len) {
     // Initiate a burst or single receive sequence
     uint cmd = --len > 0 ? I2C_MASTER_CMD_BURST_RECEIVE_START : I2C_MASTER_CMD_SINGLE_RECEIVE;
     // Set I2C codec slave address
     MAP_I2CMasterSlaveAddrSet(I2CA0_BASE, addr, true);
     // Initiate the transfer.
     RET_IF_ERR(pyb_i2c_transaction(cmd));
     // Loop until the completion of reception or error
     while (len) {
         // Receive the byte over I2C
         *data++ = MAP_I2CMasterDataGet(I2CA0_BASE);
         if (--len) {
             // Continue with reception
             RET_IF_ERR(pyb_i2c_transaction(I2C_MASTER_CMD_BURST_RECEIVE_CONT));
         } else {
             // Complete the last reception
             RET_IF_ERR(pyb_i2c_transaction(I2C_MASTER_CMD_BURST_RECEIVE_FINISH));
         }
     }

     // Receive the last byte over I2C
     *data = MAP_I2CMasterDataGet(I2CA0_BASE);
     return true;
 }

 STATIC void pyb_i2c_read_into (mp_arg_val_t *args, vstr_t *vstr) {
     pyb_i2c_check_init(&pyb_i2c_obj);
     // get the buffer to receive into
     pyb_buf_get_for_recv(args[1].u_obj, vstr);

     // receive the data
     if (!pyb_i2c_read(args[0].u_int, (byte *)vstr->buf, vstr->len)) {
         nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, mpexception_os_operation_failed));
     }
 }

 STATIC void pyb_i2c_readmem_into (mp_arg_val_t *args, vstr_t *vstr) {
     pyb_i2c_check_init(&pyb_i2c_obj);
     // get the buffer to receive into
     pyb_buf_get_for_recv(args[2].u_obj, vstr);

     // get the addresses
     mp_uint_t i2c_addr = args[0].u_int;
     mp_uint_t mem_addr = args[1].u_int;
     // determine the width of mem_addr (1 or 2 bytes)
     mp_uint_t mem_addr_size = args[3].u_int >> 3;

     // write the register address to be read from
     if (pyb_i2c_mem_addr_write (i2c_addr, (byte *)&mem_addr, mem_addr_size)) {
         // Read the specified length of data
         if (!pyb_i2c_read (i2c_addr, (byte *)vstr->buf, vstr->len)) {
             nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, mpexception_os_operation_failed));
         }
     }
 }

 /******************************************************************************/
 /* Micro Python bindings                                                      */
 /******************************************************************************/
 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;
     if (self->baudrate > 0) {
         mp_printf(print, "I2C(0, I2C.MASTER, baudrate=%u)", self->baudrate);
     } else {
         mp_print_str(print, "I2C(0)");
     }
 }

 STATIC mp_obj_t pyb_i2c_init_helper(pyb_i2c_obj_t *self, const mp_arg_val_t *args) {
     // verify that mode is master
     if (args[0].u_int != PYBI2C_MASTER) {
         goto invalid_args;
     }

     // make sure the baudrate is between the valid range
     self->baudrate = MIN(MAX(args[1].u_int, PYBI2C_MIN_BAUD_RATE_HZ), PYBI2C_MAX_BAUD_RATE_HZ);

     // assign the pins
     mp_obj_t pins_o = args[2].u_obj;
     if (pins_o != mp_const_none) {
         mp_obj_t *pins;
         if (pins_o == MP_OBJ_NULL) {
             // use the default pins
             pins = (mp_obj_t *)pyb_i2c_def_pin;
         } else {
             mp_obj_get_array_fixed_n(pins_o, 2, &pins);
         }
         pin_assign_pins_af (pins, 2, PIN_TYPE_STD_PU, PIN_FN_I2C, 0);
     }

     // init the I2C bus
     i2c_init(self);

     // register it with the sleep module
     pyb_sleep_add ((const mp_obj_t)self, (WakeUpCB_t)i2c_init);

     return mp_const_none;

 invalid_args:
     nlr_raise(mp_obj_new_exception_msg(&mp_type_ValueError, mpexception_value_invalid_arguments));
 }

 STATIC const mp_arg_t pyb_i2c_init_args[] = {
     { MP_QSTR_id,                          MP_ARG_INT, {.u_int = 0} },
     { MP_QSTR_mode,                        MP_ARG_INT, {.u_int = PYBI2C_MASTER} },
     { MP_QSTR_baudrate,  MP_ARG_KW_ONLY  | MP_ARG_INT, {.u_int = 100000} },
     { MP_QSTR_pins,      MP_ARG_KW_ONLY  | MP_ARG_OBJ, {.u_obj = MP_OBJ_NULL} },
 };
 STATIC mp_obj_t pyb_i2c_make_new(const mp_obj_type_t *type, mp_uint_t n_args, mp_uint_t n_kw, const mp_obj_t *all_args) {
     // parse args
     mp_map_t kw_args;
     mp_map_init_fixed_table(&kw_args, n_kw, all_args + n_args);
     mp_arg_val_t args[MP_ARRAY_SIZE(pyb_i2c_init_args)];
     mp_arg_parse_all(n_args, all_args, &kw_args, MP_ARRAY_SIZE(args), pyb_i2c_init_args, args);

     // check the peripheral id
     if (args[0].u_int != 0) {
         nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, mpexception_os_resource_not_avaliable));
     }

     // setup the object
     pyb_i2c_obj_t *self = &pyb_i2c_obj;
     self->base.type = &pyb_i2c_type;

     // start the peripheral
     pyb_i2c_init_helper(self, &args[1]);

     return (mp_obj_t)self;
 }

 STATIC mp_obj_t pyb_i2c_init(mp_uint_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
     // parse args
     mp_arg_val_t args[MP_ARRAY_SIZE(pyb_i2c_init_args) - 1];
     mp_arg_parse_all(n_args - 1, pos_args + 1, kw_args, MP_ARRAY_SIZE(args), &pyb_i2c_init_args[1], args);
     return pyb_i2c_init_helper(pos_args[0], args);
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_KW(pyb_i2c_init_obj, 1, pyb_i2c_init);

 STATIC mp_obj_t pyb_i2c_deinit(mp_obj_t self_in) {
     // disable the peripheral
     MAP_I2CMasterDisable(I2CA0_BASE);
     MAP_PRCMPeripheralClkDisable(PRCM_I2CA0, PRCM_RUN_MODE_CLK | PRCM_SLP_MODE_CLK);
     // invalidate the baudrate
     pyb_i2c_obj.baudrate = 0;
     // unregister it with the sleep module
     pyb_sleep_remove ((const mp_obj_t)self_in);
     return mp_const_none;
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(pyb_i2c_deinit_obj, pyb_i2c_deinit);

 STATIC mp_obj_t pyb_i2c_scan(mp_obj_t self_in) {
     pyb_i2c_check_init(&pyb_i2c_obj);
     mp_obj_t list = mp_obj_new_list(0, NULL);
     for (uint addr = 1; addr <= 127; addr++) {
         for (int i = 0; i < 7; i++) {
             if (pyb_i2c_scan_device(addr)) {
                 mp_obj_list_append(list, mp_obj_new_int(addr));
                 break;
             }
         }
     }
     return list;
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(pyb_i2c_scan_obj, pyb_i2c_scan);

 STATIC mp_obj_t pyb_i2c_readfrom(mp_uint_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
     STATIC const mp_arg_t pyb_i2c_readfrom_args[] = {
         { MP_QSTR_addr,    MP_ARG_REQUIRED | MP_ARG_INT, },
         { MP_QSTR_nbytes,  MP_ARG_REQUIRED | MP_ARG_OBJ, },
     };

     // parse args
     mp_arg_val_t args[MP_ARRAY_SIZE(pyb_i2c_readfrom_args)];
     mp_arg_parse_all(n_args - 1, pos_args + 1, kw_args, MP_ARRAY_SIZE(args), pyb_i2c_readfrom_args, args);

     vstr_t vstr;
     pyb_i2c_read_into(args, &vstr);

     // return the received data
     return mp_obj_new_str_from_vstr(&mp_type_bytes, &vstr);
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_KW(pyb_i2c_readfrom_obj, 3, pyb_i2c_readfrom);

 STATIC mp_obj_t pyb_i2c_readfrom_into(mp_uint_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
     STATIC const mp_arg_t pyb_i2c_readfrom_into_args[] = {
         { MP_QSTR_addr,    MP_ARG_REQUIRED | MP_ARG_INT, },
         { MP_QSTR_buf,     MP_ARG_REQUIRED | MP_ARG_OBJ, },
     };

     // parse args
     mp_arg_val_t args[MP_ARRAY_SIZE(pyb_i2c_readfrom_into_args)];
     mp_arg_parse_all(n_args - 1, pos_args + 1, kw_args, MP_ARRAY_SIZE(args), pyb_i2c_readfrom_into_args, args);

     vstr_t vstr;
     pyb_i2c_read_into(args, &vstr);

     // return the number of bytes received
     return mp_obj_new_int(vstr.len);
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_KW(pyb_i2c_readfrom_into_obj, 1, pyb_i2c_readfrom_into);

 STATIC mp_obj_t pyb_i2c_writeto(mp_uint_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
     STATIC const mp_arg_t pyb_i2c_writeto_args[] = {
         { MP_QSTR_addr,    MP_ARG_REQUIRED | MP_ARG_INT,  },
         { MP_QSTR_buf,     MP_ARG_REQUIRED | MP_ARG_OBJ,  },
         { MP_QSTR_stop,    MP_ARG_KW_ONLY  | MP_ARG_BOOL, {.u_bool = true} },
     };

     // parse args
     mp_arg_val_t args[MP_ARRAY_SIZE(pyb_i2c_writeto_args)];
     mp_arg_parse_all(n_args - 1, pos_args + 1, kw_args, MP_ARRAY_SIZE(args), pyb_i2c_writeto_args, args);

     pyb_i2c_check_init(&pyb_i2c_obj);

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

     // send the data
     if (!pyb_i2c_write(args[0].u_int, bufinfo.buf, bufinfo.len, args[2].u_bool)) {
         nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, mpexception_os_operation_failed));
     }

     // return the number of bytes written
     return mp_obj_new_int(bufinfo.len);
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_KW(pyb_i2c_writeto_obj, 1, pyb_i2c_writeto);

 STATIC mp_obj_t pyb_i2c_readfrom_mem(mp_uint_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
     STATIC const mp_arg_t pyb_i2c_readfrom_mem_args[] = {
         { MP_QSTR_addr,     MP_ARG_REQUIRED  | MP_ARG_INT, },
         { MP_QSTR_memaddr,  MP_ARG_REQUIRED  | MP_ARG_INT, },
         { MP_QSTR_nbytes,   MP_ARG_REQUIRED  | MP_ARG_OBJ, },
         { MP_QSTR_addrsize, MP_ARG_KW_ONLY   | MP_ARG_INT, {.u_int = 8} },
     };

     // parse args
     mp_arg_val_t args[MP_ARRAY_SIZE(pyb_i2c_readfrom_mem_args)];
     mp_arg_parse_all(n_args - 1, pos_args + 1, kw_args, MP_ARRAY_SIZE(args), pyb_i2c_readfrom_mem_args, args);

     vstr_t vstr;
     pyb_i2c_readmem_into (args, &vstr);
     return mp_obj_new_str_from_vstr(&mp_type_bytes, &vstr);
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_KW(pyb_i2c_readfrom_mem_obj, 1, pyb_i2c_readfrom_mem);

 STATIC const mp_arg_t pyb_i2c_readfrom_mem_into_args[] = {
     { MP_QSTR_addr,     MP_ARG_REQUIRED  | MP_ARG_INT, },
     { MP_QSTR_memaddr,  MP_ARG_REQUIRED  | MP_ARG_INT, },
     { MP_QSTR_buf,      MP_ARG_REQUIRED  | MP_ARG_OBJ, },
     { MP_QSTR_addrsize, MP_ARG_KW_ONLY   | MP_ARG_INT, {.u_int = 8} },
 };

 STATIC mp_obj_t pyb_i2c_readfrom_mem_into(mp_uint_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
     // parse args
     mp_arg_val_t args[MP_ARRAY_SIZE(pyb_i2c_readfrom_mem_into_args)];
     mp_arg_parse_all(n_args - 1, pos_args + 1, kw_args, MP_ARRAY_SIZE(args), pyb_i2c_readfrom_mem_into_args, args);

     // get the buffer to read into
     vstr_t vstr;
     pyb_i2c_readmem_into (args, &vstr);
     return mp_obj_new_int(vstr.len);
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_KW(pyb_i2c_readfrom_mem_into_obj, 1, pyb_i2c_readfrom_mem_into);

 STATIC mp_obj_t pyb_i2c_writeto_mem(mp_uint_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
     // parse args
     mp_arg_val_t args[MP_ARRAY_SIZE(pyb_i2c_readfrom_mem_into_args)];
     mp_arg_parse_all(n_args - 1, pos_args + 1, kw_args, MP_ARRAY_SIZE(pyb_i2c_readfrom_mem_into_args), pyb_i2c_readfrom_mem_into_args, args);

     pyb_i2c_check_init(&pyb_i2c_obj);

     // get the buffer to write from
     mp_buffer_info_t bufinfo;
     uint8_t data[1];
     pyb_buf_get_for_send(args[2].u_obj, &bufinfo, data);

     // get the addresses
     mp_uint_t i2c_addr = args[0].u_int;
     mp_uint_t mem_addr = args[1].u_int;
     // determine the width of mem_addr (1 or 2 bytes)
     mp_uint_t mem_addr_size = args[3].u_int >> 3;

     // write the register address to write to.
     if (pyb_i2c_mem_write (i2c_addr, (byte *)&mem_addr, mem_addr_size, bufinfo.buf, bufinfo.len)) {
         // return the number of bytes written
         return mp_obj_new_int(bufinfo.len);
     }

     nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, mpexception_os_operation_failed));
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_KW(pyb_i2c_writeto_mem_obj, 1, pyb_i2c_writeto_mem);

 STATIC const mp_map_elem_t pyb_i2c_locals_dict_table[] = {
     // instance methods
     { MP_OBJ_NEW_QSTR(MP_QSTR_init),                (mp_obj_t)&pyb_i2c_init_obj },
     { MP_OBJ_NEW_QSTR(MP_QSTR_deinit),              (mp_obj_t)&pyb_i2c_deinit_obj },
     { MP_OBJ_NEW_QSTR(MP_QSTR_scan),                (mp_obj_t)&pyb_i2c_scan_obj },
     { MP_OBJ_NEW_QSTR(MP_QSTR_readfrom),            (mp_obj_t)&pyb_i2c_readfrom_obj },
     { MP_OBJ_NEW_QSTR(MP_QSTR_readfrom_into),       (mp_obj_t)&pyb_i2c_readfrom_into_obj },
     { MP_OBJ_NEW_QSTR(MP_QSTR_writeto),             (mp_obj_t)&pyb_i2c_writeto_obj },
     { MP_OBJ_NEW_QSTR(MP_QSTR_readfrom_mem),        (mp_obj_t)&pyb_i2c_readfrom_mem_obj },
     { MP_OBJ_NEW_QSTR(MP_QSTR_readfrom_mem_into),   (mp_obj_t)&pyb_i2c_readfrom_mem_into_obj },
     { MP_OBJ_NEW_QSTR(MP_QSTR_writeto_mem),         (mp_obj_t)&pyb_i2c_writeto_mem_obj },

     // class constants
     { MP_OBJ_NEW_QSTR(MP_QSTR_MASTER),              MP_OBJ_NEW_SMALL_INT(PYBI2C_MASTER) },
 };

 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_t)&pyb_i2c_locals_dict,
 };
	/*
	* This file is part of the Micro Python project, http://micropython.org/
	*
	* The MIT License (MIT)
	*
	* Copyright (c) 2013, 2014 Damien P. George
	* Copyright (c) 2015 Daniel Campora
	*
	* 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/mpstate.h"
	#include "py/runtime.h"
	#include "py/mphal.h"
	#include "bufhelper.h"
	#include "inc/hw_types.h"
	#include "inc/hw_i2c.h"
	#include "inc/hw_ints.h"
	#include "inc/hw_memmap.h"
	#include "rom_map.h"
	#include "pin.h"
	#include "prcm.h"
	#include "i2c.h"
	#include "pybi2c.h"
	#include "mpexception.h"
	#include "pybsleep.h"
	#include "utils.h"
	#include "pybpin.h"
	#include "pins.h"

	/// \moduleref pyb
	/// \class I2C - a two-wire serial protocol

	typedef struct _pyb_i2c_obj_t {
	mp_obj_base_t base;
	uint baudrate;
	} pyb_i2c_obj_t;

	/******************************************************************************
	DEFINE CONSTANTS
	******************************************************************************/
	#define PYBI2C_MASTER (0)

	#define PYBI2C_MIN_BAUD_RATE_HZ (50000)
	#define PYBI2C_MAX_BAUD_RATE_HZ (400000)

	#define PYBI2C_TRANSC_TIMEOUT_MS (10)
	#define PYBI2C_TRANSAC_WAIT_DELAY_US (10)

	#define PYBI2C_TIMEOUT_TO_COUNT(to_us, baud) (((baud) * to_us) / 16000000)

	#define RET_IF_ERR(Func) { \
	if (!Func) { \
	return false; \
	} \
	}

	/******************************************************************************
	DECLARE PRIVATE DATA
	******************************************************************************/
	STATIC pyb_i2c_obj_t pyb_i2c_obj = {.baudrate = 0};

	STATIC const mp_obj_t pyb_i2c_def_pin[2] = {&pin_GP13, &pin_GP23};

	/******************************************************************************
	DEFINE PRIVATE FUNCTIONS
	******************************************************************************/
	// only master mode is available for the moment
	STATIC void i2c_init (pyb_i2c_obj_t *self) {
	// Enable the I2C Peripheral
	MAP_PRCMPeripheralClkEnable(PRCM_I2CA0, PRCM_RUN_MODE_CLK \| PRCM_SLP_MODE_CLK);
	MAP_PRCMPeripheralReset(PRCM_I2CA0);
	// Configure I2C module with the specified baudrate
	MAP_I2CMasterInitExpClk(I2CA0_BASE, self->baudrate);
	}

	STATIC bool pyb_i2c_transaction(uint cmd) {
	// Convert the timeout to microseconds
	int32_t timeout = PYBI2C_TRANSC_TIMEOUT_MS * 1000;
	// Sanity check, t_timeout must be between 1 and 255
	uint t_timeout = MIN(PYBI2C_TIMEOUT_TO_COUNT(timeout, pyb_i2c_obj.baudrate), 255);
	// Clear all interrupts
	MAP_I2CMasterIntClearEx(I2CA0_BASE, MAP_I2CMasterIntStatusEx(I2CA0_BASE, false));
	// Set the time-out in terms of clock cycles. Not to be used with breakpoints.
	MAP_I2CMasterTimeoutSet(I2CA0_BASE, t_timeout);
	// Initiate the transfer.
	MAP_I2CMasterControl(I2CA0_BASE, cmd);
	// Wait until the current byte has been transferred.
	// Poll on the raw interrupt status.
	while ((MAP_I2CMasterIntStatusEx(I2CA0_BASE, false) & (I2C_MASTER_INT_DATA \| I2C_MASTER_INT_TIMEOUT)) == 0) {
	// wait for a few microseconds
	UtilsDelay(UTILS_DELAY_US_TO_COUNT(PYBI2C_TRANSAC_WAIT_DELAY_US));
	timeout -= PYBI2C_TRANSAC_WAIT_DELAY_US;
	if (timeout < 0) {
	// the peripheral is not responding, so stop
	return false;
	}
	}

	// Check for any errors in the transfer
	if (MAP_I2CMasterErr(I2CA0_BASE) != I2C_MASTER_ERR_NONE) {
	switch(cmd) {
	case I2C_MASTER_CMD_BURST_SEND_START:
	case I2C_MASTER_CMD_BURST_SEND_CONT:
	case I2C_MASTER_CMD_BURST_SEND_STOP:
	MAP_I2CMasterControl(I2CA0_BASE, I2C_MASTER_CMD_BURST_SEND_ERROR_STOP);
	break;
	case I2C_MASTER_CMD_BURST_RECEIVE_START:
	case I2C_MASTER_CMD_BURST_RECEIVE_CONT:
	case I2C_MASTER_CMD_BURST_RECEIVE_FINISH:
	MAP_I2CMasterControl(I2CA0_BASE, I2C_MASTER_CMD_BURST_RECEIVE_ERROR_STOP);
	break;
	default:
	break;
	}
	return false;
	}
	return true;
	}

	STATIC void pyb_i2c_check_init(pyb_i2c_obj_t *self) {
	// not initialized
	if (!self->baudrate) {
	nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, mpexception_os_request_not_possible));
	}
	}

	STATIC bool pyb_i2c_scan_device(byte devAddr) {
	// Set I2C codec slave address
	MAP_I2CMasterSlaveAddrSet(I2CA0_BASE, devAddr, true);
	// Initiate the transfer.
	RET_IF_ERR(pyb_i2c_transaction(I2C_MASTER_CMD_SINGLE_RECEIVE));
	// Since this is a hack, send the stop bit anyway
	MAP_I2CMasterControl(I2CA0_BASE, I2C_MASTER_CMD_BURST_SEND_ERROR_STOP);
	return true;
	}

	STATIC bool pyb_i2c_mem_addr_write (byte addr, byte *mem_addr, uint mem_addr_len) {
	// Set I2C codec slave address
	MAP_I2CMasterSlaveAddrSet(I2CA0_BASE, addr, false);
	// Write the first byte to the controller.
	MAP_I2CMasterDataPut(I2CA0_BASE, *mem_addr++);
	// Initiate the transfer.
	RET_IF_ERR(pyb_i2c_transaction(I2C_MASTER_CMD_BURST_SEND_START));

	// Loop until the completion of transfer or error
	while (--mem_addr_len) {
	// Write the next byte of data
	MAP_I2CMasterDataPut(I2CA0_BASE, *mem_addr++);
	// Transact over I2C to send the next byte
	RET_IF_ERR(pyb_i2c_transaction(I2C_MASTER_CMD_BURST_SEND_CONT));
	}
	return true;
	}

	STATIC bool pyb_i2c_mem_write (byte addr, byte mem_addr, uint mem_addr_len, byte data, uint data_len) {
	if (pyb_i2c_mem_addr_write (addr, mem_addr, mem_addr_len)) {
	// Loop until the completion of transfer or error
	while (data_len--) {
	// Write the next byte of data
	MAP_I2CMasterDataPut(I2CA0_BASE, *data++);
	// Transact over I2C to send the byte
	RET_IF_ERR(pyb_i2c_transaction(I2C_MASTER_CMD_BURST_SEND_CONT));
	}
	// send the stop bit
	RET_IF_ERR(pyb_i2c_transaction(I2C_MASTER_CMD_BURST_SEND_STOP));
	return true;
	}
	return false;
	}

	STATIC bool pyb_i2c_write(byte addr, byte *data, uint len, bool stop) {
	// Set I2C codec slave address
	MAP_I2CMasterSlaveAddrSet(I2CA0_BASE, addr, false);
	// Write the first byte to the controller.
	MAP_I2CMasterDataPut(I2CA0_BASE, *data++);
	// Initiate the transfer.
	RET_IF_ERR(pyb_i2c_transaction(I2C_MASTER_CMD_BURST_SEND_START));

	// Loop until the completion of transfer or error
	while (--len) {
	// Write the next byte of data
	MAP_I2CMasterDataPut(I2CA0_BASE, *data++);
	// Transact over I2C to send the byte
	RET_IF_ERR(pyb_i2c_transaction(I2C_MASTER_CMD_BURST_SEND_CONT));
	}

	// If a stop bit is to be sent, do it.
	if (stop) {
	RET_IF_ERR(pyb_i2c_transaction(I2C_MASTER_CMD_BURST_SEND_STOP));
	}
	return true;
	}

	STATIC bool pyb_i2c_read(byte addr, byte *data, uint len) {
	// Initiate a burst or single receive sequence
	uint cmd = --len > 0 ? I2C_MASTER_CMD_BURST_RECEIVE_START : I2C_MASTER_CMD_SINGLE_RECEIVE;
	// Set I2C codec slave address
	MAP_I2CMasterSlaveAddrSet(I2CA0_BASE, addr, true);
	// Initiate the transfer.
	RET_IF_ERR(pyb_i2c_transaction(cmd));
	// Loop until the completion of reception or error
	while (len) {
	// Receive the byte over I2C
	*data++ = MAP_I2CMasterDataGet(I2CA0_BASE);
	if (--len) {
	// Continue with reception
	RET_IF_ERR(pyb_i2c_transaction(I2C_MASTER_CMD_BURST_RECEIVE_CONT));
	} else {
	// Complete the last reception
	RET_IF_ERR(pyb_i2c_transaction(I2C_MASTER_CMD_BURST_RECEIVE_FINISH));
	}
	}

	// Receive the last byte over I2C
	*data = MAP_I2CMasterDataGet(I2CA0_BASE);
	return true;
	}

	STATIC void pyb_i2c_read_into (mp_arg_val_t args, vstr_t vstr) {
	pyb_i2c_check_init(&pyb_i2c_obj);
	// get the buffer to receive into
	pyb_buf_get_for_recv(args[1].u_obj, vstr);

	// receive the data
	if (!pyb_i2c_read(args[0].u_int, (byte *)vstr->buf, vstr->len)) {
	nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, mpexception_os_operation_failed));
	}
	}

	STATIC void pyb_i2c_readmem_into (mp_arg_val_t args, vstr_t vstr) {
	pyb_i2c_check_init(&pyb_i2c_obj);
	// get the buffer to receive into
	pyb_buf_get_for_recv(args[2].u_obj, vstr);

	// get the addresses
	mp_uint_t i2c_addr = args[0].u_int;
	mp_uint_t mem_addr = args[1].u_int;
	// determine the width of mem_addr (1 or 2 bytes)
	mp_uint_t mem_addr_size = args[3].u_int >> 3;

	// write the register address to be read from
	if (pyb_i2c_mem_addr_write (i2c_addr, (byte *)&mem_addr, mem_addr_size)) {
	// Read the specified length of data
	if (!pyb_i2c_read (i2c_addr, (byte *)vstr->buf, vstr->len)) {
	nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, mpexception_os_operation_failed));
	}
	}
	}

	/******************************************************************************/
	/* Micro Python bindings */
	/******************************************************************************/
	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;
	if (self->baudrate > 0) {
	mp_printf(print, "I2C(0, I2C.MASTER, baudrate=%u)", self->baudrate);
	} else {
	mp_print_str(print, "I2C(0)");
	}
	}

	STATIC mp_obj_t pyb_i2c_init_helper(pyb_i2c_obj_t self, const mp_arg_val_t args) {
	// verify that mode is master
	if (args[0].u_int != PYBI2C_MASTER) {
	goto invalid_args;
	}

	// make sure the baudrate is between the valid range
	self->baudrate = MIN(MAX(args[1].u_int, PYBI2C_MIN_BAUD_RATE_HZ), PYBI2C_MAX_BAUD_RATE_HZ);

	// assign the pins
	mp_obj_t pins_o = args[2].u_obj;
	if (pins_o != mp_const_none) {
	mp_obj_t *pins;
	if (pins_o == MP_OBJ_NULL) {
	// use the default pins
	pins = (mp_obj_t *)pyb_i2c_def_pin;
	} else {
	mp_obj_get_array_fixed_n(pins_o, 2, &pins);
	}
	pin_assign_pins_af (pins, 2, PIN_TYPE_STD_PU, PIN_FN_I2C, 0);
	}

	// init the I2C bus
	i2c_init(self);

	// register it with the sleep module
	pyb_sleep_add ((const mp_obj_t)self, (WakeUpCB_t)i2c_init);

	return mp_const_none;

	invalid_args:
	nlr_raise(mp_obj_new_exception_msg(&mp_type_ValueError, mpexception_value_invalid_arguments));
	}

	STATIC const mp_arg_t pyb_i2c_init_args[] = {
	{ MP_QSTR_id, MP_ARG_INT, {.u_int = 0} },
	{ MP_QSTR_mode, MP_ARG_INT, {.u_int = PYBI2C_MASTER} },
	{ MP_QSTR_baudrate, MP_ARG_KW_ONLY \| MP_ARG_INT, {.u_int = 100000} },
	{ MP_QSTR_pins, MP_ARG_KW_ONLY \| MP_ARG_OBJ, {.u_obj = MP_OBJ_NULL} },
	};
	STATIC mp_obj_t pyb_i2c_make_new(const mp_obj_type_t type, mp_uint_t n_args, mp_uint_t n_kw, const mp_obj_t all_args) {
	// parse args
	mp_map_t kw_args;
	mp_map_init_fixed_table(&kw_args, n_kw, all_args + n_args);
	mp_arg_val_t args[MP_ARRAY_SIZE(pyb_i2c_init_args)];
	mp_arg_parse_all(n_args, all_args, &kw_args, MP_ARRAY_SIZE(args), pyb_i2c_init_args, args);

	// check the peripheral id
	if (args[0].u_int != 0) {
	nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, mpexception_os_resource_not_avaliable));
	}

	// setup the object
	pyb_i2c_obj_t *self = &pyb_i2c_obj;
	self->base.type = &pyb_i2c_type;

	// start the peripheral
	pyb_i2c_init_helper(self, &args[1]);

	return (mp_obj_t)self;
	}

	STATIC mp_obj_t pyb_i2c_init(mp_uint_t n_args, const mp_obj_t pos_args, mp_map_t kw_args) {
	// parse args
	mp_arg_val_t args[MP_ARRAY_SIZE(pyb_i2c_init_args) - 1];
	mp_arg_parse_all(n_args - 1, pos_args + 1, kw_args, MP_ARRAY_SIZE(args), &pyb_i2c_init_args[1], args);
	return pyb_i2c_init_helper(pos_args[0], args);
	}
	STATIC MP_DEFINE_CONST_FUN_OBJ_KW(pyb_i2c_init_obj, 1, pyb_i2c_init);

	STATIC mp_obj_t pyb_i2c_deinit(mp_obj_t self_in) {
	// disable the peripheral
	MAP_I2CMasterDisable(I2CA0_BASE);
	MAP_PRCMPeripheralClkDisable(PRCM_I2CA0, PRCM_RUN_MODE_CLK \| PRCM_SLP_MODE_CLK);
	// invalidate the baudrate
	pyb_i2c_obj.baudrate = 0;
	// unregister it with the sleep module
	pyb_sleep_remove ((const mp_obj_t)self_in);
	return mp_const_none;
	}
	STATIC MP_DEFINE_CONST_FUN_OBJ_1(pyb_i2c_deinit_obj, pyb_i2c_deinit);

	STATIC mp_obj_t pyb_i2c_scan(mp_obj_t self_in) {
	pyb_i2c_check_init(&pyb_i2c_obj);
	mp_obj_t list = mp_obj_new_list(0, NULL);
	for (uint addr = 1; addr <= 127; addr++) {
	for (int i = 0; i < 7; i++) {
	if (pyb_i2c_scan_device(addr)) {
	mp_obj_list_append(list, mp_obj_new_int(addr));
	break;
	}
	}
	}
	return list;
	}
	STATIC MP_DEFINE_CONST_FUN_OBJ_1(pyb_i2c_scan_obj, pyb_i2c_scan);

	STATIC mp_obj_t pyb_i2c_readfrom(mp_uint_t n_args, const mp_obj_t pos_args, mp_map_t kw_args) {
	STATIC const mp_arg_t pyb_i2c_readfrom_args[] = {
	{ MP_QSTR_addr, MP_ARG_REQUIRED \| MP_ARG_INT, },
	{ MP_QSTR_nbytes, MP_ARG_REQUIRED \| MP_ARG_OBJ, },
	};

	// parse args
	mp_arg_val_t args[MP_ARRAY_SIZE(pyb_i2c_readfrom_args)];
	mp_arg_parse_all(n_args - 1, pos_args + 1, kw_args, MP_ARRAY_SIZE(args), pyb_i2c_readfrom_args, args);

	vstr_t vstr;
	pyb_i2c_read_into(args, &vstr);

	// return the received data
	return mp_obj_new_str_from_vstr(&mp_type_bytes, &vstr);
	}
	STATIC MP_DEFINE_CONST_FUN_OBJ_KW(pyb_i2c_readfrom_obj, 3, pyb_i2c_readfrom);

	STATIC mp_obj_t pyb_i2c_readfrom_into(mp_uint_t n_args, const mp_obj_t pos_args, mp_map_t kw_args) {
	STATIC const mp_arg_t pyb_i2c_readfrom_into_args[] = {
	{ MP_QSTR_addr, MP_ARG_REQUIRED \| MP_ARG_INT, },
	{ MP_QSTR_buf, MP_ARG_REQUIRED \| MP_ARG_OBJ, },
	};

	// parse args
	mp_arg_val_t args[MP_ARRAY_SIZE(pyb_i2c_readfrom_into_args)];
	mp_arg_parse_all(n_args - 1, pos_args + 1, kw_args, MP_ARRAY_SIZE(args), pyb_i2c_readfrom_into_args, args);

	vstr_t vstr;
	pyb_i2c_read_into(args, &vstr);

	// return the number of bytes received
	return mp_obj_new_int(vstr.len);
	}
	STATIC MP_DEFINE_CONST_FUN_OBJ_KW(pyb_i2c_readfrom_into_obj, 1, pyb_i2c_readfrom_into);

	STATIC mp_obj_t pyb_i2c_writeto(mp_uint_t n_args, const mp_obj_t pos_args, mp_map_t kw_args) {
	STATIC const mp_arg_t pyb_i2c_writeto_args[] = {
	{ MP_QSTR_addr, MP_ARG_REQUIRED \| MP_ARG_INT, },
	{ MP_QSTR_buf, MP_ARG_REQUIRED \| MP_ARG_OBJ, },
	{ MP_QSTR_stop, MP_ARG_KW_ONLY \| MP_ARG_BOOL, {.u_bool = true} },
	};

	// parse args
	mp_arg_val_t args[MP_ARRAY_SIZE(pyb_i2c_writeto_args)];
	mp_arg_parse_all(n_args - 1, pos_args + 1, kw_args, MP_ARRAY_SIZE(args), pyb_i2c_writeto_args, args);

	pyb_i2c_check_init(&pyb_i2c_obj);

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

	// send the data
	if (!pyb_i2c_write(args[0].u_int, bufinfo.buf, bufinfo.len, args[2].u_bool)) {
	nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, mpexception_os_operation_failed));
	}

	// return the number of bytes written
	return mp_obj_new_int(bufinfo.len);
	}
	STATIC MP_DEFINE_CONST_FUN_OBJ_KW(pyb_i2c_writeto_obj, 1, pyb_i2c_writeto);

	STATIC mp_obj_t pyb_i2c_readfrom_mem(mp_uint_t n_args, const mp_obj_t pos_args, mp_map_t kw_args) {
	STATIC const mp_arg_t pyb_i2c_readfrom_mem_args[] = {
	{ MP_QSTR_addr, MP_ARG_REQUIRED \| MP_ARG_INT, },
	{ MP_QSTR_memaddr, MP_ARG_REQUIRED \| MP_ARG_INT, },
	{ MP_QSTR_nbytes, MP_ARG_REQUIRED \| MP_ARG_OBJ, },
	{ MP_QSTR_addrsize, MP_ARG_KW_ONLY \| MP_ARG_INT, {.u_int = 8} },
	};

	// parse args
	mp_arg_val_t args[MP_ARRAY_SIZE(pyb_i2c_readfrom_mem_args)];
	mp_arg_parse_all(n_args - 1, pos_args + 1, kw_args, MP_ARRAY_SIZE(args), pyb_i2c_readfrom_mem_args, args);

	vstr_t vstr;
	pyb_i2c_readmem_into (args, &vstr);
	return mp_obj_new_str_from_vstr(&mp_type_bytes, &vstr);
	}
	STATIC MP_DEFINE_CONST_FUN_OBJ_KW(pyb_i2c_readfrom_mem_obj, 1, pyb_i2c_readfrom_mem);

	STATIC const mp_arg_t pyb_i2c_readfrom_mem_into_args[] = {
	{ MP_QSTR_addr, MP_ARG_REQUIRED \| MP_ARG_INT, },
	{ MP_QSTR_memaddr, MP_ARG_REQUIRED \| MP_ARG_INT, },
	{ MP_QSTR_buf, MP_ARG_REQUIRED \| MP_ARG_OBJ, },
	{ MP_QSTR_addrsize, MP_ARG_KW_ONLY \| MP_ARG_INT, {.u_int = 8} },
	};

	STATIC mp_obj_t pyb_i2c_readfrom_mem_into(mp_uint_t n_args, const mp_obj_t pos_args, mp_map_t kw_args) {
	// parse args
	mp_arg_val_t args[MP_ARRAY_SIZE(pyb_i2c_readfrom_mem_into_args)];
	mp_arg_parse_all(n_args - 1, pos_args + 1, kw_args, MP_ARRAY_SIZE(args), pyb_i2c_readfrom_mem_into_args, args);

	// get the buffer to read into
	vstr_t vstr;
	pyb_i2c_readmem_into (args, &vstr);
	return mp_obj_new_int(vstr.len);
	}
	STATIC MP_DEFINE_CONST_FUN_OBJ_KW(pyb_i2c_readfrom_mem_into_obj, 1, pyb_i2c_readfrom_mem_into);

	STATIC mp_obj_t pyb_i2c_writeto_mem(mp_uint_t n_args, const mp_obj_t pos_args, mp_map_t kw_args) {
	// parse args
	mp_arg_val_t args[MP_ARRAY_SIZE(pyb_i2c_readfrom_mem_into_args)];
	mp_arg_parse_all(n_args - 1, pos_args + 1, kw_args, MP_ARRAY_SIZE(pyb_i2c_readfrom_mem_into_args), pyb_i2c_readfrom_mem_into_args, args);

	pyb_i2c_check_init(&pyb_i2c_obj);

	// get the buffer to write from
	mp_buffer_info_t bufinfo;
	uint8_t data[1];
	pyb_buf_get_for_send(args[2].u_obj, &bufinfo, data);

	// get the addresses
	mp_uint_t i2c_addr = args[0].u_int;
	mp_uint_t mem_addr = args[1].u_int;
	// determine the width of mem_addr (1 or 2 bytes)
	mp_uint_t mem_addr_size = args[3].u_int >> 3;

	// write the register address to write to.
	if (pyb_i2c_mem_write (i2c_addr, (byte *)&mem_addr, mem_addr_size, bufinfo.buf, bufinfo.len)) {
	// return the number of bytes written
	return mp_obj_new_int(bufinfo.len);
	}

	nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, mpexception_os_operation_failed));
	}
	STATIC MP_DEFINE_CONST_FUN_OBJ_KW(pyb_i2c_writeto_mem_obj, 1, pyb_i2c_writeto_mem);

	STATIC const mp_map_elem_t pyb_i2c_locals_dict_table[] = {
	// instance methods
	{ MP_OBJ_NEW_QSTR(MP_QSTR_init), (mp_obj_t)&pyb_i2c_init_obj },
	{ MP_OBJ_NEW_QSTR(MP_QSTR_deinit), (mp_obj_t)&pyb_i2c_deinit_obj },
	{ MP_OBJ_NEW_QSTR(MP_QSTR_scan), (mp_obj_t)&pyb_i2c_scan_obj },
	{ MP_OBJ_NEW_QSTR(MP_QSTR_readfrom), (mp_obj_t)&pyb_i2c_readfrom_obj },
	{ MP_OBJ_NEW_QSTR(MP_QSTR_readfrom_into), (mp_obj_t)&pyb_i2c_readfrom_into_obj },
	{ MP_OBJ_NEW_QSTR(MP_QSTR_writeto), (mp_obj_t)&pyb_i2c_writeto_obj },
	{ MP_OBJ_NEW_QSTR(MP_QSTR_readfrom_mem), (mp_obj_t)&pyb_i2c_readfrom_mem_obj },
	{ MP_OBJ_NEW_QSTR(MP_QSTR_readfrom_mem_into), (mp_obj_t)&pyb_i2c_readfrom_mem_into_obj },
	{ MP_OBJ_NEW_QSTR(MP_QSTR_writeto_mem), (mp_obj_t)&pyb_i2c_writeto_mem_obj },

	// class constants
	{ MP_OBJ_NEW_QSTR(MP_QSTR_MASTER), MP_OBJ_NEW_SMALL_INT(PYBI2C_MASTER) },
	};

	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_t)&pyb_i2c_locals_dict,
	};