esp8266: Add basic I2C driver, with init and writeto methods.

Tested and working with SSD1306 I2C display.

esp8266/Makefile

@@ -61,6 +61,7 @@ SRC_C = \
 	modpybpin.c \
 	modpybrtc.c \
 	modpybadc.c \
+	modpybi2c.c \
 	modesp.c \
 	modnetwork.c \
 	modutime.c \

esp8266/modmachine.c

@@ -142,6 +142,7 @@ STATIC const mp_rom_map_elem_t machine_module_globals_table[] = {
 
     { MP_ROM_QSTR(MP_QSTR_Timer), MP_ROM_PTR(&esp_timer_type) },
     { MP_ROM_QSTR(MP_QSTR_Pin), MP_ROM_PTR(&pyb_pin_type) },
+    { MP_ROM_QSTR(MP_QSTR_I2C), MP_ROM_PTR(&pyb_i2c_type) },
 };
 
 STATIC MP_DEFINE_CONST_DICT(machine_module_globals, machine_module_globals_table);

esp8266/modpyb.h

 extern const mp_obj_type_t pyb_pin_type;
 extern const mp_obj_type_t pyb_adc_type;
 extern const mp_obj_type_t pyb_rtc_type;
+extern const mp_obj_type_t pyb_i2c_type;
 
 typedef struct _pyb_pin_obj_t {
     mp_obj_base_t base;

esp8266/modpybi2c.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 "ets_sys.h"
+#include "osapi.h"
+#include "gpio.h"
+
+#include "py/runtime.h"
+#include "modpyb.h"
+
+typedef struct _pyb_i2c_obj_t {
+    mp_obj_base_t base;
+    pyb_pin_obj_t *scl;
+    pyb_pin_obj_t *sda;
+    uint8_t prev_sda;
+    uint8_t prev_scl;
+} pyb_i2c_obj_t;
+
+// these set the frequency of SCL
+#define mphal_i2c_wait_a() os_delay_us(2)
+#define mphal_i2c_wait_b() os_delay_us(1)
+
+STATIC void mphal_i2c_set_sda_scl(pyb_i2c_obj_t *self, uint8_t sda, uint8_t scl) {
+    sda &= 0x01;
+    scl &= 0x01;
+    self->prev_sda = sda;
+    self->prev_scl = scl;
+    gpio_output_set((sda << self->sda->phys_port) | (scl << self->scl->phys_port),
+        ((1 - sda) << self->sda->phys_port) | ((1 - scl) << self->scl->phys_port),
+        (1 << self->sda->phys_port) | (1 << self->scl->phys_port), 0);
+}
+
+STATIC int mphal_i2c_get_sda(pyb_i2c_obj_t *self) {
+    return GPIO_INPUT_GET(GPIO_ID_PIN(self->sda->phys_port));
+}
+
+STATIC void mphal_i2c_start(pyb_i2c_obj_t *self) {
+    mphal_i2c_set_sda_scl(self, 1, self->prev_scl);
+    mphal_i2c_wait_a();
+    mphal_i2c_set_sda_scl(self, 1, 1);
+    mphal_i2c_wait_a();
+    mphal_i2c_set_sda_scl(self, 0, 1);
+    mphal_i2c_wait_a();
+}
+
+STATIC void mphal_i2c_stop(pyb_i2c_obj_t *self) {
+    mphal_i2c_wait_a();
+    mphal_i2c_set_sda_scl(self, 0, self->prev_scl);
+    mphal_i2c_wait_a();
+    mphal_i2c_set_sda_scl(self, 0, 1);
+    mphal_i2c_wait_a();
+    mphal_i2c_set_sda_scl(self, 1, 1);
+    mphal_i2c_wait_a();
+}
+
+STATIC void mphal_i2c_init(pyb_i2c_obj_t *self, uint32_t freq) {
+    pyb_pin_obj_t *scl = self->scl;
+    pyb_pin_obj_t *sda = self->sda;
+
+    ETS_GPIO_INTR_DISABLE();
+    //ETS_INTR_LOCK();
+
+    PIN_FUNC_SELECT(sda->periph, sda->func);
+    PIN_FUNC_SELECT(scl->periph, scl->func);
+
+    GPIO_REG_WRITE(GPIO_PIN_ADDR(GPIO_ID_PIN(sda->phys_port)),
+        GPIO_REG_READ(GPIO_PIN_ADDR(GPIO_ID_PIN(sda->phys_port)))
+        | GPIO_PIN_PAD_DRIVER_SET(GPIO_PAD_DRIVER_ENABLE)); // open drain
+    GPIO_REG_WRITE(GPIO_ENABLE_ADDRESS,
+        GPIO_REG_READ(GPIO_ENABLE_ADDRESS) | (1 << sda->phys_port));
+    GPIO_REG_WRITE(GPIO_PIN_ADDR(GPIO_ID_PIN(scl->phys_port)),
+        GPIO_REG_READ(GPIO_PIN_ADDR(GPIO_ID_PIN(scl->phys_port)))
+        | GPIO_PIN_PAD_DRIVER_SET(GPIO_PAD_DRIVER_ENABLE)); // open drain
+    GPIO_REG_WRITE(GPIO_ENABLE_ADDRESS,
+        GPIO_REG_READ(GPIO_ENABLE_ADDRESS) | (1 << scl->phys_port));
+
+    mphal_i2c_set_sda_scl(self, 1, 1);
+
+    ETS_GPIO_INTR_ENABLE();
+    //ETS_INTR_UNLOCK();
+
+    mphal_i2c_set_sda_scl(self, 1, 0);
+    mphal_i2c_wait_a();
+
+    // when SCL = 0, toggle SDA to clear up
+    mphal_i2c_set_sda_scl(self, 0, 0);
+    mphal_i2c_wait_a();
+    mphal_i2c_set_sda_scl(self, 1, 0);
+    mphal_i2c_wait_a();
+
+    // set data_cnt to max value
+    for (uint8_t i = 0; i < 28; i++) {
+        mphal_i2c_set_sda_scl(self, 1, 0);
+        mphal_i2c_wait_a();
+        mphal_i2c_set_sda_scl(self, 1, 1);
+        mphal_i2c_wait_a();
+    }
+
+    // reset all
+    mphal_i2c_stop(self);
+}
+
+STATIC int mphal_i2c_write_byte(pyb_i2c_obj_t *self, uint8_t val) {
+    uint8_t dat;
+    sint8 i;
+
+    mphal_i2c_wait_a();
+
+    mphal_i2c_set_sda_scl(self, self->prev_sda, 0);
+    mphal_i2c_wait_a();
+
+    for (i = 7; i >= 0; i--) {
+        dat = val >> i;
+        mphal_i2c_set_sda_scl(self, dat, 0);
+        mphal_i2c_wait_a();
+        mphal_i2c_set_sda_scl(self, dat, 1);
+        mphal_i2c_wait_a();
+
+        if (i == 0) {
+            mphal_i2c_wait_b();
+        }
+
+        mphal_i2c_set_sda_scl(self, dat, 0);
+        mphal_i2c_wait_a();
+    }
+
+    mphal_i2c_set_sda_scl(self, self->prev_sda, 0);
+    mphal_i2c_wait_a();
+    mphal_i2c_set_sda_scl(self, 1, 0);
+    mphal_i2c_wait_a();
+    mphal_i2c_set_sda_scl(self, 1, 1);
+    mphal_i2c_wait_a();
+
+    int ret = mphal_i2c_get_sda(self);
+    mphal_i2c_wait_a();
+    mphal_i2c_set_sda_scl(self, 1, 0);
+    mphal_i2c_wait_a();
+
+    return !ret;
+}
+
+STATIC void mphal_i2c_write(pyb_i2c_obj_t *self, uint8_t addr, uint8_t *data, size_t len, bool stop) {
+    mphal_i2c_start(self);
+    if (!mphal_i2c_write_byte(self, addr << 1)) {
+        goto er;
+    }
+    while (len--) {
+        if (!mphal_i2c_write_byte(self, *data++)) {
+            goto er;
+        }
+    }
+    if (stop) {
+        mphal_i2c_stop(self);
+    }
+    return;
+
+er:
+    mphal_i2c_stop(self);
+    nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, "I2C bus error"));
+}
+
+/******************************************************************************/
+// MicroPython bindings for I2C
+
+STATIC void pyb_i2c_obj_init_helper(pyb_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_obj_get_pin_obj(args[ARG_scl].u_obj);
+    self->sda = mp_obj_get_pin_obj(args[ARG_sda].u_obj);
+    mphal_i2c_init(self, args[ARG_freq].u_int);
+}
+
+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) {
+    mp_arg_check_num(n_args, n_kw, 0, MP_OBJ_FUN_ARGS_MAX, true);
+    pyb_i2c_obj_t *self = m_new_obj(pyb_i2c_obj_t);
+    self->base.type = &pyb_i2c_type;
+    mp_map_t kw_args;
+    mp_map_init_fixed_table(&kw_args, n_kw, args + n_args);
+    pyb_i2c_obj_init_helper(self, n_args, args, &kw_args);
+    return (mp_obj_t)self;
+}
+
+STATIC mp_obj_t pyb_i2c_obj_init(mp_uint_t n_args, const mp_obj_t *args, mp_map_t *kw_args) {
+    pyb_i2c_obj_init_helper(args[0], n_args - 1, args + 1, kw_args);
+    return mp_const_none;
+}
+MP_DEFINE_CONST_FUN_OBJ_KW(pyb_i2c_init_obj, 1, pyb_i2c_obj_init);
+
+STATIC mp_obj_t pyb_i2c_writeto(mp_uint_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
+    enum { ARG_addr, ARG_buf, ARG_stop };
+    static const mp_arg_t allowed_args[] = {
+        { MP_QSTR_addr, MP_ARG_REQUIRED | MP_ARG_INT, {.u_int = 0} },
+        { MP_QSTR_buf,  MP_ARG_REQUIRED | MP_ARG_OBJ, {.u_obj = MP_OBJ_NULL} },
+        { MP_QSTR_stop, MP_ARG_KW_ONLY | MP_ARG_BOOL, {.u_bool = true} },
+    };
+    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 write from
+    mp_buffer_info_t bufinfo;
+    mp_get_buffer_raise(args[ARG_buf].u_obj, &bufinfo, MP_BUFFER_READ);
+
+    // do the I2C transfer
+    mphal_i2c_write(self, args[ARG_addr].u_int, bufinfo.buf, bufinfo.len, args[ARG_stop].u_bool);
+
+    return mp_const_none;
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_KW(pyb_i2c_writeto_obj, 1, pyb_i2c_writeto);
+
+STATIC const mp_rom_map_elem_t pyb_i2c_locals_dict_table[] = {
+    { MP_ROM_QSTR(MP_QSTR_init),    MP_ROM_PTR(&pyb_i2c_init_obj) },
+    { MP_ROM_QSTR(MP_QSTR_writeto), MP_ROM_PTR(&pyb_i2c_writeto_obj) },
+};
+
+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,
+    .make_new = pyb_i2c_make_new,
+    .locals_dict = (mp_obj_dict_t*)&pyb_i2c_locals_dict,
+};

esp8266/qstrdefsport.h

@@ -142,6 +142,17 @@ Q(memory)
 Q(ADC)
 Q(read)
 
+// I2C
+Q(I2C)
+Q(init)
+Q(scl)
+Q(sda)
+Q(freq)
+Q(writeto)
+Q(stop)
+Q(buf)
+Q(addr)
+
 // utime
 Q(utime)
 Q(localtime)