zephyr/i2c: Add support for hardware i2c.

Adds support for hardware i2c to the zephyr port. Similar to other ports
such as stm32 and nrf, we only implement the i2c protocol functions
(readfrom and writeto) and defer memory operations (readfrom_mem,
readfrom_mem_into, and writeto_mem) to the software i2c implementation.
This may need to change in the future because zephyr is considering
deprecating its i2c_transfer function in favor of i2c_write_read; in this
case we would probably want to implement the memory operations directly
using i2c_write_read.

Tested with the accelerometer on frdm_k64f and bbc_microbit boards.

9 files changed, 165 insertions, 2 deletions

diff --git a/ports/zephyr/Makefile b/ports/zephyr/Makefile
index 8e71d7f08..b23ee1093 100644
--- a/ports/zephyr/Makefile
+++ b/ports/zephyr/Makefile
@@ -43,6 +43,7 @@ SRC_C = main.c \
 	modzephyr.c \
 	modzsensor.c \
 	modmachine.c \
+	machine_i2c.c \
 	machine_pin.c \
 	uart_core.c \
 	lib/utils/stdout_helpers.c \
diff --git a/ports/zephyr/README.md b/ports/zephyr/README.md
index f7001af4b..3d2e883ad 100644
--- a/ports/zephyr/README.md
+++ b/ports/zephyr/README.md
@@ -12,6 +12,7 @@ Features supported at this time:
 
 * REPL (interactive prompt) over Zephyr UART console.
 * `utime` module for time measurements and delays.
+* `machine.I2C` class for I2C control.
 * `machine.Pin` class for GPIO control.
 * `usocket` module for networking (IPv4/IPv6).
 * "Frozen modules" support to allow to bundle Python modules together
@@ -81,6 +82,13 @@ To blink an LED:
         LED.value(0)
         time.sleep(0.5)
 
+To scan for I2C slaves:
+
+    from machine import I2C
+
+    i2c = I2C("I2C_0")
+    i2c.scan()
+
 The above code uses an LED location for a FRDM-K64F board (port B, pin 21;
 following Zephyr conventions port are identified by "GPIO_x", where *x*
 starts from 0). You will need to adjust it for another board (using board's
diff --git a/ports/zephyr/machine_i2c.c b/ports/zephyr/machine_i2c.c
new file mode 100644
index 000000000..bc9851a00
--- /dev/null
+++ b/ports/zephyr/machine_i2c.c
@@ -0,0 +1,145 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2013, 2014, 2015 Damien P. George
+ * Copyright (c) 2019, NXP
+ *
+ * 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 <zephyr.h>
+#include <i2c.h>
+
+#include "py/runtime.h"
+#include "py/gc.h"
+#include "py/mphal.h"
+#include "py/mperrno.h"
+#include "extmod/machine_i2c.h"
+
+STATIC const mp_obj_type_t machine_hard_i2c_type;
+
+typedef struct _machine_hard_i2c_obj_t {
+    mp_obj_base_t base;
+    struct device *dev;
+    bool restart;
+} machine_hard_i2c_obj_t;
+
+STATIC void machine_hard_i2c_print(const mp_print_t *print, mp_obj_t self_in, mp_print_kind_t kind) {
+    machine_hard_i2c_obj_t *self = self_in;
+    mp_printf(print, "%s", self->dev->config->name);
+}
+
+mp_obj_t machine_hard_i2c_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *all_args) {
+    enum { ARG_id, ARG_scl, ARG_sda, ARG_freq, ARG_timeout };
+    static const mp_arg_t allowed_args[] = {
+        { MP_QSTR_id, MP_ARG_REQUIRED | MP_ARG_OBJ },
+        { MP_QSTR_scl, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_obj = MP_OBJ_NULL} },
+        { MP_QSTR_sda, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_obj = MP_OBJ_NULL} },
+        { MP_QSTR_freq, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_obj = MP_OBJ_NULL} },
+        { MP_QSTR_timeout, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_obj = MP_OBJ_NULL} },
+    };
+
+    mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
+    mp_arg_parse_all_kw_array(n_args, n_kw, all_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
+
+    const char *dev_name = mp_obj_str_get_str(args[ARG_id].u_obj);
+    struct device *dev = device_get_binding(dev_name);
+
+    if (dev == NULL) {
+        mp_raise_ValueError("device not found");
+    }
+
+    if ((args[ARG_scl].u_obj != MP_OBJ_NULL) || (args[ARG_sda].u_obj != MP_OBJ_NULL)) {
+        mp_raise_NotImplementedError("explicit choice of scl/sda is not implemented");
+    }
+
+    if ((args[ARG_freq].u_obj != MP_OBJ_NULL)) {
+        mp_raise_NotImplementedError("explicit choice of freq is not implemented");
+    }
+
+    if ((args[ARG_timeout].u_obj != MP_OBJ_NULL)) {
+        mp_raise_NotImplementedError("explicit choice of timeout is not implemented");
+    }
+
+    machine_hard_i2c_obj_t *self = m_new_obj(machine_hard_i2c_obj_t);
+
+    self->base.type = &machine_hard_i2c_type;
+    self->dev = dev;
+    self->restart = false;
+
+    return MP_OBJ_FROM_PTR(self);
+}
+
+STATIC int machine_hard_i2c_transfer(mp_obj_base_t *self_in, uint16_t addr, uint8_t *buf, size_t len, bool stop, bool read) {
+    machine_hard_i2c_obj_t *self = (machine_hard_i2c_obj_t *)self_in;
+    struct i2c_msg msg;
+    int ret;
+
+    msg.buf = (u8_t*)buf;
+    msg.len = len;
+    msg.flags = 0;
+
+    if (read) {
+        msg.flags |= I2C_MSG_READ;
+    } else {
+        msg.flags |= I2C_MSG_WRITE;
+    }
+
+    if (self->restart) {
+        msg.flags |= I2C_MSG_RESTART;
+    }
+
+    if (stop) {
+        msg.flags |= I2C_MSG_STOP;
+        self->restart = false;
+    } else {
+        self->restart = true;
+    }
+
+    ret = i2c_transfer(self->dev, &msg, 1, addr);
+    return (ret < 0) ? -MP_EIO : len;
+}
+
+STATIC int machine_hard_i2c_readfrom(mp_obj_base_t *self_in, uint16_t addr, uint8_t *dest, size_t len, bool stop) {
+    return machine_hard_i2c_transfer(self_in, addr, dest, len, stop, true);
+}
+
+STATIC int machine_hard_i2c_writeto(mp_obj_base_t *self_in, uint16_t addr, const uint8_t *src, size_t len, bool stop) {
+    return machine_hard_i2c_transfer(self_in, addr, (uint8_t*)src, len, stop, false);
+}
+
+STATIC const mp_machine_i2c_p_t machine_hard_i2c_p = {
+    .readfrom = machine_hard_i2c_readfrom,
+    .writeto = machine_hard_i2c_writeto,
+};
+
+STATIC const mp_obj_type_t machine_hard_i2c_type = {
+    { &mp_type_type },
+    .name = MP_QSTR_I2C,
+    .print = machine_hard_i2c_print,
+    .make_new = machine_hard_i2c_make_new,
+    .protocol = &machine_hard_i2c_p,
+    .locals_dict = (mp_obj_dict_t*)&mp_machine_soft_i2c_locals_dict,
+};
diff --git a/ports/zephyr/modmachine.c b/ports/zephyr/modmachine.c
index 5909c37d6..c89529aa9 100644
--- a/ports/zephyr/modmachine.c
+++ b/ports/zephyr/modmachine.c
@@ -60,6 +60,7 @@ STATIC const mp_rom_map_elem_t machine_module_globals_table[] = {
     #endif
     { MP_ROM_QSTR(MP_QSTR_reset_cause), MP_ROM_PTR(&machine_reset_cause_obj) },
 
+    { MP_ROM_QSTR(MP_QSTR_I2C), MP_ROM_PTR(&machine_i2c_type) },
     { MP_ROM_QSTR(MP_QSTR_Pin), MP_ROM_PTR(&machine_pin_type) },
     { MP_ROM_QSTR(MP_QSTR_Signal), MP_ROM_PTR(&machine_signal_type) },
 
diff --git a/ports/zephyr/mpconfigport.h b/ports/zephyr/mpconfigport.h
index ab5560108..0b35de35b 100644
--- a/ports/zephyr/mpconfigport.h
+++ b/ports/zephyr/mpconfigport.h
@@ -60,6 +60,8 @@
 #define MICROPY_PY_IO               (0)
 #define MICROPY_PY_MICROPYTHON_MEM_INFO (1)
 #define MICROPY_PY_MACHINE          (1)
+#define MICROPY_PY_MACHINE_I2C      (1)
+#define MICROPY_PY_MACHINE_I2C_MAKE_NEW machine_hard_i2c_make_new
 #define MICROPY_PY_MACHINE_PIN_MAKE_NEW mp_pin_make_new
 #define MICROPY_MODULE_WEAK_LINKS   (1)
 #define MICROPY_PY_STRUCT           (0)
diff --git a/ports/zephyr/mphalport.h b/ports/zephyr/mphalport.h
index e3cca8d37..4388f607d 100644
--- a/ports/zephyr/mphalport.h
+++ b/ports/zephyr/mphalport.h
@@ -23,3 +23,8 @@ static inline void mp_hal_delay_us(mp_uint_t delay) {
 static inline void mp_hal_delay_ms(mp_uint_t delay) {
     k_sleep(delay);
 }
+
+#define mp_hal_delay_us_fast(us)   (mp_hal_delay_us(us))
+#define mp_hal_pin_od_low(p)       (mp_raise_NotImplementedError("mp_hal_pin_od_low"))
+#define mp_hal_pin_od_high(p)      (mp_raise_NotImplementedError("mp_hal_pin_od_high"))
+#define mp_hal_pin_open_drain(p)   (mp_raise_NotImplementedError("mp_hal_pin_open_drain"))
diff --git a/ports/zephyr/prj_base.conf b/ports/zephyr/prj_base.conf
index 993dfdc26..58206a0bc 100644
--- a/ports/zephyr/prj_base.conf
+++ b/ports/zephyr/prj_base.conf
@@ -14,6 +14,9 @@ CONFIG_NEWLIB_LIBC=y
 CONFIG_FLOAT=y
 CONFIG_MAIN_STACK_SIZE=4736
 
+# Drivers
+CONFIG_I2C=y
+
 # Enable sensor subsystem (doesn't add code if not used).
 # Specific sensors should be enabled per-board.
 CONFIG_SENSOR=y
diff --git a/ports/zephyr/prj_frdm_k64f.conf b/ports/zephyr/prj_frdm_k64f.conf
index c974bffb6..477f3b825 100644
--- a/ports/zephyr/prj_frdm_k64f.conf
+++ b/ports/zephyr/prj_frdm_k64f.conf
@@ -2,7 +2,6 @@
 CONFIG_NET_L2_ETHERNET=y
 
 # Sensor drivers
-CONFIG_I2C=y
 CONFIG_FXOS8700=y
 CONFIG_FXOS8700_MODE_HYBRID=y
 CONFIG_FXOS8700_TEMP=y
diff --git a/ports/zephyr/prj_frdm_kw41z.conf b/ports/zephyr/prj_frdm_kw41z.conf
index de5182002..486ece2bd 100644
--- a/ports/zephyr/prj_frdm_kw41z.conf
+++ b/ports/zephyr/prj_frdm_kw41z.conf
@@ -1,5 +1,4 @@
 # Sensor drivers
-CONFIG_I2C=y
 CONFIG_FXOS8700=y
 CONFIG_FXOS8700_MODE_HYBRID=y
 CONFIG_FXOS8700_TEMP=y