codal_port: Correctly acquire and free I2C and SPI pins.

This makes sure that pins that are currently used for I2C and SPI are in
the correct pin mode, and pins that were previously but no longer used for
I2C/SPI are freed.

Fixes issue #167.

Signed-off-by: Damien George <damien@micropython.org>

Author: dpgeorge

src/codal_port/microbit_i2c.c

@@ -31,6 +31,8 @@
 
 typedef struct _microbit_i2c_obj_t {
     mp_obj_base_t base;
+    const microbit_pin_obj_t *scl;
+    const microbit_pin_obj_t *sda;
 } microbit_i2c_obj_t;
 
 STATIC mp_obj_t microbit_i2c_init(mp_uint_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
@@ -55,8 +57,12 @@ STATIC mp_obj_t microbit_i2c_init(mp_uint_t n_args, const mp_obj_t *pos_args, mp
         scl = microbit_obj_get_pin(args[ARG_scl].u_obj);
     }
 
+    // Acquire new pins and free the previous ones.
+    microbit_obj_pin_acquire_and_free(&microbit_i2c_obj.scl, scl, microbit_pin_mode_i2c);
+    microbit_obj_pin_acquire_and_free(&microbit_i2c_obj.sda, sda, microbit_pin_mode_i2c);
+
     // Initialise the I2C bus.
-    int ret =microbit_hal_i2c_init(scl->name, sda->name, args[ARG_freq].u_int);
+    int ret = microbit_hal_i2c_init(scl->name, sda->name, args[ARG_freq].u_int);
 
     if (ret != 0) {
         mp_raise_OSError(ret);
@@ -149,6 +155,8 @@ STATIC MP_DEFINE_CONST_OBJ_TYPE(
     locals_dict, &microbit_i2c_locals_dict
     );
 
-const microbit_i2c_obj_t microbit_i2c_obj = {
+microbit_i2c_obj_t microbit_i2c_obj = {
     { &microbit_i2c_type },
+    .scl = &microbit_p19_obj,
+    .sda = &microbit_p20_obj,
 };

src/codal_port/microbit_spi.c

@@ -32,6 +32,9 @@
 
 typedef struct _microbit_spi_obj_t {
     mp_obj_base_t base;
+    const microbit_pin_obj_t *sclk;
+    const microbit_pin_obj_t *mosi;
+    const microbit_pin_obj_t *miso;
 } microbit_spi_obj_t;
 
 STATIC bool microbit_spi_initialised = false;
@@ -71,12 +74,10 @@ STATIC mp_obj_t microbit_spi_init(mp_uint_t n_args, const mp_obj_t *pos_args, mp
         miso = microbit_obj_get_pin(args[ARG_miso].u_obj);
     }
 
-    // Initialise the pins.
-    // Note: the pins are not freed, so init'ing the SPI a second time on
-    // different pins will leave the old pins still in SPI mode.
-    microbit_obj_pin_acquire(sclk, microbit_pin_mode_spi);
-    microbit_obj_pin_acquire(mosi, microbit_pin_mode_spi);
-    microbit_obj_pin_acquire(miso, microbit_pin_mode_spi);
+    // Acquire new pins and free the previous ones.
+    microbit_obj_pin_acquire_and_free(&microbit_spi_obj.sclk, sclk, microbit_pin_mode_spi);
+    microbit_obj_pin_acquire_and_free(&microbit_spi_obj.mosi, mosi, microbit_pin_mode_spi);
+    microbit_obj_pin_acquire_and_free(&microbit_spi_obj.miso, miso, microbit_pin_mode_spi);
 
     // Initialise the SPI bus.
     int ret = microbit_hal_spi_init(sclk->name, mosi->name, miso->name,
@@ -147,6 +148,9 @@ STATIC MP_DEFINE_CONST_OBJ_TYPE(
     locals_dict, &microbit_spi_locals_dict
     );
 
-const microbit_spi_obj_t microbit_spi_obj = {
+microbit_spi_obj_t microbit_spi_obj = {
     { &microbit_spi_type },
+    .sclk = &microbit_p13_obj,
+    .mosi = &microbit_p15_obj,
+    .miso = &microbit_p14_obj,
 };

src/codal_port/modmicrobit.h

@@ -111,9 +111,9 @@ extern const struct _microbit_pin_obj_t microbit_p20_obj;
 extern const struct _microbit_pin_obj_t microbit_pin_logo_obj;
 extern const struct _microbit_pin_obj_t microbit_pin_speaker_obj;
 
-extern const struct _microbit_i2c_obj_t microbit_i2c_obj;
+extern struct _microbit_i2c_obj_t microbit_i2c_obj;
 extern const struct _microbit_uart_obj_t microbit_uart_obj;
-extern const struct _microbit_spi_obj_t microbit_spi_obj;
+extern struct _microbit_spi_obj_t microbit_spi_obj;
 
 extern const struct _monochrome_5by5_t microbit_const_image_heart_obj;
 extern const struct _monochrome_5by5_t microbit_const_image_heart_small_obj;