Add support for MicroBitI2C.set/get_frequency().

inc/genhdr/qstrdefs.generated.h

@@ -500,6 +500,7 @@ QDEF(MP_QSTR_clear_calibration, (const byte*)"\x49\x11" "clear_calibration")
 QDEF(MP_QSTR_get_field_strength, (const byte*)"\xf4\x12" "get_field_strength")
 QDEF(MP_QSTR_MicroBitI2C, (const byte*)"\xb8\x0b" "MicroBitI2C")
 QDEF(MP_QSTR_i2c, (const byte*)"\x5d\x03" "i2c")
+QDEF(MP_QSTR_set_frequency, (const byte*)"\x5c\x0d" "set_frequency")
 QDEF(MP_QSTR_addr, (const byte*)"\xb6\x04" "addr")
 QDEF(MP_QSTR_n, (const byte*)"\xcb\x01" "n")
 QDEF(MP_QSTR_buf, (const byte*)"\x74\x03" "buf")

inc/microbit/modmicrobit.h

@@ -186,6 +186,7 @@ MP_DECLARE_CONST_FUN_OBJ(microbit_pin_write_analog_obj);
 MP_DECLARE_CONST_FUN_OBJ(microbit_pin_is_touched_obj);
 MP_DECLARE_CONST_FUN_OBJ(microbit_pin_set_analog_period_obj);
 MP_DECLARE_CONST_FUN_OBJ(microbit_pin_set_analog_period_microseconds_obj);
+MP_DECLARE_CONST_FUN_OBJ(microbit_i2c_set_frequency_obj);
 MP_DECLARE_CONST_FUN_OBJ(microbit_i2c_read_obj);
 MP_DECLARE_CONST_FUN_OBJ(microbit_i2c_write_obj);
 MP_DECLARE_CONST_FUN_OBJ(microbit_image_width_obj);

inc/microbit/qstrdefsport.h

@@ -191,6 +191,7 @@ Q(get_field_strength)
 
 Q(MicroBitI2C)
 Q(i2c)
+Q(set_frequency)
 Q(read)
 Q(write)
 Q(addr)

source/microbit/help.c

@@ -132,6 +132,7 @@ STATIC const mp_doc_t help_table_instances[] = {
     {&microbit_pin_is_touched_obj, "If pin is_touched() on micro:bit, return True. If nothing is touching the pin,\nreturn False.\n"},
     // I2C
     {&microbit_i2c_obj, "Communicate with one or more named devices connected to micro:bit. Each named\ndevice has an 'address', communicates using I2C, and connects to the I/O pins.\n"},
+    {&microbit_i2c_set_frequency_obj, "Use set_frequency(f) to set the I2C bus frequency.\n"},
     {&microbit_i2c_read_obj, "Use read(address, n) to read 'n' bytes from the device with this address.\n"},
     {&microbit_i2c_write_obj, "Use write(address, buffer) to write to the 'buffer' of the device at this 'address'.\n"},
     // Image

source/microbit/microbiti2c.cpp

@@ -36,6 +36,35 @@ typedef struct _microbit_i2c_obj_t {
     MicroBitI2C *i2c;
 } microbit_i2c_obj_t;
 
+STATIC mp_obj_t microbit_i2c_set_frequency(mp_obj_t self_in, mp_obj_t frequency_in) {
+    microbit_i2c_obj_t *self = (microbit_i2c_obj_t*)self_in;
+    int frequency = mp_obj_get_int(frequency_in);
+
+    /* Workaround: This is built with knowledge from
+     * mbed-classic/targets/hal/TARGET_NORDIC/TARGET_MCU_NRF51822/i2c_api.c
+     * which clamps the frequency to one of the following values.  The mbed
+     * API doesn't support return values and DAL doesn't support getting the
+     * frequency (it's protected with no getter).  We prefer to raise a
+     * ValueError when the frequency isn't one of the supported frequencies
+     * instead of clamping it silently.
+     *
+     * Note: If the default frequency changes, please update the initialized
+     * value at the bottom of this file.
+     */
+    switch (frequency) {
+    case 100000: /* 100 KHz */
+    case 250000: /* 250 KHz */
+    case 400000: /* 400 KHz */
+        break;
+    default:
+        nlr_raise(mp_obj_new_exception_msg(&mp_type_ValueError, "Invalid frequency"));
+    }
+
+    self->i2c->frequency(frequency);
+    return mp_const_none;
+}
+MP_DEFINE_CONST_FUN_OBJ_2(microbit_i2c_set_frequency_obj, microbit_i2c_set_frequency);
+
 STATIC mp_obj_t microbit_i2c_read(mp_uint_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
     static const mp_arg_t allowed_args[] = {
         { MP_QSTR_addr,     MP_ARG_REQUIRED | MP_ARG_INT, {.u_int = 0} },
@@ -85,6 +114,7 @@ STATIC mp_obj_t microbit_i2c_write(mp_uint_t n_args, const mp_obj_t *pos_args, m
 MP_DEFINE_CONST_FUN_OBJ_KW(microbit_i2c_write_obj, 1, microbit_i2c_write);
 
 STATIC const mp_map_elem_t microbit_i2c_locals_dict_table[] = {
+    { MP_OBJ_NEW_QSTR(MP_QSTR_set_frequency), (mp_obj_t)&microbit_i2c_set_frequency_obj },
     { MP_OBJ_NEW_QSTR(MP_QSTR_read), (mp_obj_t)&microbit_i2c_read_obj },
     { MP_OBJ_NEW_QSTR(MP_QSTR_write), (mp_obj_t)&microbit_i2c_write_obj },
 };
@@ -111,7 +141,7 @@ const mp_obj_type_t microbit_i2c_type = {
 
 const microbit_i2c_obj_t microbit_i2c_obj = {
     {&microbit_i2c_type},
-    .i2c = &uBit.i2c
+    .i2c = &uBit.i2c,
 };
 
 }