extmod: Add generic machine.I2C class, with bit-bang I2C.

Should work on any machine that provides the correct pin functions.

extmod/machine_i2c.c

+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2016 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 <stdint.h>
+#include <string.h>
+
+#include "py/mphal.h"
+#include "py/runtime.h"
+#include "extmod/machine_i2c.h"
+
+#if MICROPY_PY_MACHINE_I2C
+
+typedef struct _machine_i2c_obj_t {
+    mp_obj_base_t base;
+    uint32_t us_delay;
+    mp_hal_pin_obj_t *scl;
+    mp_hal_pin_obj_t *sda;
+} 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_low(self->scl);
+}
+
+STATIC void mp_hal_i2c_scl_release(machine_i2c_obj_t *self) {
+    mp_hal_pin_od_high(self->scl);
+}
+
+STATIC void mp_hal_i2c_sda_low(machine_i2c_obj_t *self) {
+    mp_hal_pin_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 void mp_hal_i2c_start(machine_i2c_obj_t *self) {
+    mp_hal_i2c_sda_release(self);
+    mp_hal_i2c_delay(self);
+    mp_hal_i2c_scl_release(self);
+    mp_hal_i2c_delay(self);
+    mp_hal_i2c_sda_low(self);
+    mp_hal_i2c_delay(self);
+}
+
+STATIC void 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);
+    mp_hal_i2c_scl_release(self);
+    mp_hal_i2c_delay(self);
+    mp_hal_i2c_sda_release(self);
+    mp_hal_i2c_delay(self);
+}
+
+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_config_od(self->scl);
+    mp_hal_pin_config_od(self->sda);
+    mp_hal_i2c_stop(self);
+}
+
+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);
+        mp_hal_i2c_scl_release(self);
+        mp_hal_i2c_delay(self);
+        mp_hal_i2c_scl_low(self);
+    }
+
+    mp_hal_i2c_sda_release(self);
+    mp_hal_i2c_delay(self);
+    mp_hal_i2c_scl_release(self);
+    mp_hal_i2c_delay(self);
+
+    int ret = mp_hal_i2c_sda_read(self);
+    mp_hal_i2c_delay(self);
+    mp_hal_i2c_scl_low(self);
+
+    return !ret;
+}
+
+STATIC void mp_hal_i2c_write(machine_i2c_obj_t *self, uint8_t addr, uint8_t *data, size_t len) {
+    mp_hal_i2c_start(self);
+    if (!mp_hal_i2c_write_byte(self, addr << 1)) {
+        goto er;
+    }
+    while (len--) {
+        if (!mp_hal_i2c_write_byte(self, *data++)) {
+            goto er;
+        }
+    }
+    return;
+
+er:
+    mp_hal_i2c_stop(self);
+    nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, "I2C bus error"));
+}
+
+STATIC int mp_hal_i2c_read_byte(machine_i2c_obj_t *self, uint8_t *val) {
+    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--) {
+        mp_hal_i2c_scl_release(self);
+        mp_hal_i2c_delay(self);
+        data = (data << 1) | mp_hal_i2c_sda_read(self);
+        mp_hal_i2c_scl_low(self);
+        mp_hal_i2c_delay(self);
+    }
+    *val = data;
+
+    mp_hal_i2c_scl_release(self);
+    mp_hal_i2c_delay(self);
+    mp_hal_i2c_scl_low(self);
+    mp_hal_i2c_delay(self);
+
+    return 1; // success
+}
+
+STATIC void mp_hal_i2c_read(machine_i2c_obj_t *self, uint8_t addr, uint8_t *data, size_t len) {
+    mp_hal_i2c_start(self);
+    if (!mp_hal_i2c_write_byte(self, (addr << 1) | 1)) {
+        goto er;
+    }
+    while (len--) {
+        if (!mp_hal_i2c_read_byte(self, data++)) {
+            goto er;
+        }
+    }
+    return;
+
+er:
+    mp_hal_i2c_stop(self);
+    nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, "I2C bus error"));
+}
+
+/******************************************************************************/
+// MicroPython bindings for I2C
+
+STATIC void machine_i2c_obj_init_helper(machine_i2c_obj_t *self, mp_uint_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
+    enum { ARG_scl, ARG_sda, ARG_freq };
+    static const mp_arg_t allowed_args[] = {
+        { MP_QSTR_scl, MP_ARG_REQUIRED | MP_ARG_OBJ },
+        { MP_QSTR_sda, MP_ARG_REQUIRED | MP_ARG_OBJ },
+        { MP_QSTR_freq, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 400000} },
+    };
+    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);
+    mp_hal_i2c_init(self, args[ARG_freq].u_int);
+}
+
+STATIC mp_obj_t machine_i2c_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *args) {
+    mp_arg_check_num(n_args, n_kw, 0, MP_OBJ_FUN_ARGS_MAX, true);
+    machine_i2c_obj_t *self = m_new_obj(machine_i2c_obj_t);
+    self->base.type = &machine_i2c_type;
+    mp_map_t kw_args;
+    mp_map_init_fixed_table(&kw_args, n_kw, args + n_args);
+    machine_i2c_obj_init_helper(self, n_args, args, &kw_args);
+    return (mp_obj_t)self;
+}
+
+STATIC mp_obj_t machine_i2c_obj_init(size_t n_args, const mp_obj_t *args, mp_map_t *kw_args) {
+    machine_i2c_obj_init_helper(args[0], n_args - 1, args + 1, kw_args);
+    return mp_const_none;
+}
+MP_DEFINE_CONST_FUN_OBJ_KW(machine_i2c_init_obj, 1, machine_i2c_obj_init);
+
+STATIC mp_obj_t machine_i2c_scan(mp_obj_t self_in) {
+    machine_i2c_obj_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) {
+        mp_hal_i2c_start(self);
+        int ack = mp_hal_i2c_write_byte(self, (addr << 1) | 1);
+        if (ack) {
+            mp_obj_list_append(list, MP_OBJ_NEW_SMALL_INT(addr));
+        }
+        mp_hal_i2c_stop(self);
+    }
+    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) {
+    machine_i2c_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    mp_hal_i2c_start(self);
+    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) {
+    machine_i2c_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    mp_hal_i2c_stop(self);
+    return mp_const_none;
+}
+MP_DEFINE_CONST_FUN_OBJ_1(machine_i2c_stop_obj, machine_i2c_stop);
+
+STATIC mp_obj_t machine_i2c_readinto(mp_obj_t self_in, mp_obj_t buf_in) {
+    machine_i2c_obj_t *self = MP_OBJ_TO_PTR(self_in);
+
+    // get the buffer to read into
+    mp_buffer_info_t bufinfo;
+    mp_get_buffer_raise(buf_in, &bufinfo, MP_BUFFER_WRITE);
+
+    // do the read
+    uint8_t *dest = bufinfo.buf;
+    while (bufinfo.len--) {
+        if (!mp_hal_i2c_read_byte(self, dest++)) {
+            nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, "I2C bus error"));
+        }
+    }
+
+    return mp_const_none;
+}
+MP_DEFINE_CONST_FUN_OBJ_2(machine_i2c_readinto_obj, machine_i2c_readinto);
+
+STATIC mp_obj_t machine_i2c_write(mp_obj_t self_in, mp_obj_t buf_in) {
+    machine_i2c_obj_t *self = MP_OBJ_TO_PTR(self_in);
+
+    // get the buffer to write from
+    mp_buffer_info_t bufinfo;
+    mp_get_buffer_raise(buf_in, &bufinfo, MP_BUFFER_READ);
+
+    // do the write
+    uint8_t *src = bufinfo.buf;
+    while (bufinfo.len--) {
+        if (!mp_hal_i2c_write_byte(self, *src++)) {
+            nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, "I2C bus error"));
+        }
+    }
+
+    return mp_const_none;
+}
+MP_DEFINE_CONST_FUN_OBJ_2(machine_i2c_write_obj, machine_i2c_write);
+
+STATIC mp_obj_t machine_i2c_readfrom(mp_obj_t self_in, mp_obj_t addr_in, mp_obj_t nbytes_in) {
+    machine_i2c_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    vstr_t vstr;
+    vstr_init_len(&vstr, mp_obj_get_int(nbytes_in));
+    mp_hal_i2c_read(self, mp_obj_get_int(addr_in), (uint8_t*)vstr.buf, vstr.len);
+    return mp_obj_new_str_from_vstr(&mp_type_bytes, &vstr);
+}
+MP_DEFINE_CONST_FUN_OBJ_3(machine_i2c_readfrom_obj, machine_i2c_readfrom);
+
+STATIC mp_obj_t machine_i2c_readfrom_into(mp_obj_t self_in, mp_obj_t addr_in, mp_obj_t buf_in) {
+    machine_i2c_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    mp_buffer_info_t bufinfo;
+    mp_get_buffer_raise(buf_in, &bufinfo, MP_BUFFER_WRITE);
+    mp_hal_i2c_read(self, mp_obj_get_int(addr_in), (uint8_t*)bufinfo.buf, bufinfo.len);
+    return mp_const_none;
+}
+MP_DEFINE_CONST_FUN_OBJ_3(machine_i2c_readfrom_into_obj, machine_i2c_readfrom_into);
+
+STATIC mp_obj_t machine_i2c_writeto(mp_obj_t self_in, mp_obj_t addr_in, mp_obj_t buf_in) {
+    machine_i2c_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    mp_buffer_info_t bufinfo;
+    mp_get_buffer_raise(buf_in, &bufinfo, MP_BUFFER_READ);
+    mp_hal_i2c_write(self, mp_obj_get_int(addr_in), bufinfo.buf, bufinfo.len);
+    return mp_const_none;
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_3(machine_i2c_writeto_obj, machine_i2c_writeto);
+
+STATIC mp_obj_t machine_i2c_readfrom_mem(size_t n_args, const mp_obj_t *args, mp_map_t *kw_args) {
+    mp_not_implemented("I2C.readfrom_mem");
+}
+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 *args, mp_map_t *kw_args) {
+    mp_not_implemented("I2C.readfrom_mem_into");
+}
+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 *args, mp_map_t *kw_args) {
+    mp_not_implemented("I2C.writeto_mem");
+}
+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) },
+
+    // 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) },
+};
+
+STATIC MP_DEFINE_CONST_DICT(machine_i2c_locals_dict, machine_i2c_locals_dict_table);
+
+const mp_obj_type_t machine_i2c_type = {
+    { &mp_type_type },
+    .name = MP_QSTR_I2C,
+    .make_new = machine_i2c_make_new,
+    .locals_dict = (mp_obj_dict_t*)&machine_i2c_locals_dict,
+};
+
+#endif // MICROPY_PY_MACHINE_I2C

extmod/machine_i2c.h

+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2016 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.
+ */
+
+#ifndef __MICROPY_INCLUDED_EXTMOD_MACHINE_I2C_H__
+#define __MICROPY_INCLUDED_EXTMOD_MACHINE_I2C_H__
+
+#include "py/obj.h"
+
+extern const mp_obj_type_t machine_i2c_type;
+
+#endif // __MICROPY_INCLUDED_EXTMOD_MACHINE_I2C_H__

py/mpconfig.h

@@ -837,6 +837,10 @@ typedef double mp_float_t;
 #define MICROPY_PY_MACHINE (0)
 #endif
 
+#ifndef MICROPY_PY_MACHINE_I2C
+#define MICROPY_PY_MACHINE_I2C (0)
+#endif
+
 #ifndef MICROPY_PY_USSL
 #define MICROPY_PY_USSL (0)
 #endif

py/py.mk

@@ -167,6 +167,7 @@ PY_O_BASENAME = \
 	../extmod/moduhashlib.o \
 	../extmod/modubinascii.o \
 	../extmod/machine_mem.o \
+	../extmod/machine_i2c.o \
 	../extmod/modussl.o \
 	../extmod/modurandom.o \
 	../extmod/modwebsocket.o \

py/qstrdefs.h

@@ -681,6 +681,26 @@ Q(mem16)
 Q(mem32)
 #endif
 
+#if MICROPY_PY_MACHINE_I2C
+Q(I2C)
+Q(init)
+Q(scl)
+Q(sda)
+Q(freq)
+Q(scan)
+Q(start)
+Q(stop)
+Q(read)
+Q(readinto)
+Q(write)
+Q(readfrom)
+Q(readfrom_into)
+Q(writeto)
+Q(readfrom_mem)
+Q(readfrom_mem_into)
+Q(writeto_mem)
+#endif
+
 #if MICROPY_PY_USSL
 Q(ussl)
 Q(wrap_socket)