stmhal: Add a function for setting the pin alternate function

mp_hal_gpio_set_af will search for a given function and unit
and set the alternate function to the alternate function index
found.

stmhal/i2c.c

@@ -217,32 +217,30 @@ void i2c_init(I2C_HandleTypeDef *i2c) {
     GPIO_InitStructure.Speed = GPIO_SPEED_FAST;
     GPIO_InitStructure.Pull = GPIO_NOPULL; // have external pull-up resistors on both lines
 
-    const pyb_i2c_obj_t *self;
-    const pin_obj_t *pins[2];
+    int i2c_unit;
+    const pin_obj_t *scl_pin;
+    const pin_obj_t *sda_pin;
 
     if (0) {
     #if defined(MICROPY_HW_I2C1_SCL)
     } else if (i2c == &I2CHandle1) {
-        self = &pyb_i2c_obj[0];
-        pins[0] = &MICROPY_HW_I2C1_SCL;
-        pins[1] = &MICROPY_HW_I2C1_SDA;
-        GPIO_InitStructure.Alternate = GPIO_AF4_I2C1;
+        i2c_unit = 1;
+        scl_pin = &MICROPY_HW_I2C1_SCL;
+        sda_pin = &MICROPY_HW_I2C1_SDA;
         __I2C1_CLK_ENABLE();
     #endif
     #if defined(MICROPY_HW_I2C2_SCL)
     } else if (i2c == &I2CHandle2) {
-        self = &pyb_i2c_obj[1];
-        pins[0] = &MICROPY_HW_I2C2_SCL;
-        pins[1] = &MICROPY_HW_I2C2_SDA;
-        GPIO_InitStructure.Alternate = GPIO_AF4_I2C2;
+        i2c_unit = 2;
+        scl_pin = &MICROPY_HW_I2C2_SCL;
+        sda_pin = &MICROPY_HW_I2C2_SDA;
         __I2C2_CLK_ENABLE();
     #endif
     #if defined(MICROPY_HW_I2C3_SCL)
     } else if (i2c == &I2CHandle3) {
-        self = &pyb_i2c_obj[2];
-        pins[0] = &MICROPY_HW_I2C3_SCL;
-        pins[1] = &MICROPY_HW_I2C3_SDA;
-        GPIO_InitStructure.Alternate = GPIO_AF4_I2C3;
+        i2c_unit = 3;
+        scl_pin = &MICROPY_HW_I2C3_SCL;
+        sda_pin = &MICROPY_HW_I2C3_SDA;
         __I2C3_CLK_ENABLE();
     #endif
     } else {
@@ -251,11 +249,8 @@ void i2c_init(I2C_HandleTypeDef *i2c) {
     }
 
     // init the GPIO lines
-    for (uint i = 0; i < 2; i++) {
-        mp_hal_gpio_clock_enable(pins[i]->gpio);
-        GPIO_InitStructure.Pin = pins[i]->pin_mask;
-        HAL_GPIO_Init(pins[i]->gpio, &GPIO_InitStructure);
-    }
+    mp_hal_gpio_set_af(scl_pin, &GPIO_InitStructure, AF_FN_I2C, i2c_unit);
+    mp_hal_gpio_set_af(sda_pin, &GPIO_InitStructure, AF_FN_I2C, i2c_unit);
 
     // init the I2C device
     if (HAL_I2C_Init(i2c) != HAL_OK) {
@@ -267,6 +262,7 @@ void i2c_init(I2C_HandleTypeDef *i2c) {
     }
 
     // invalidate the DMA channels so they are initialised on first use
+    const pyb_i2c_obj_t *self = &pyb_i2c_obj[i2c_unit - 1];
     dma_invalidate_channel(self->tx_dma_stream, self->tx_dma_channel);
     dma_invalidate_channel(self->rx_dma_stream, self->rx_dma_channel);
 }

stmhal/mphalport.c

@@ -118,3 +118,17 @@ void mp_hal_gpio_clock_enable(GPIO_TypeDef *gpio) {
     #endif
     }
 }
+
+bool mp_hal_gpio_set_af(const pin_obj_t *pin, GPIO_InitTypeDef *init, uint8_t fn, uint8_t unit) {
+    mp_hal_gpio_clock_enable(pin->gpio);
+
+    const pin_af_obj_t *af = pin_find_af(pin, fn, unit);
+    if (af == NULL) {
+        return false;
+    }
+    init->Pin = pin->pin_mask;
+    init->Alternate = af->idx;
+    HAL_GPIO_Init(pin->gpio, init);
+
+    return true;
+}

stmhal/mphalport.h

 // We use the ST Cube HAL library for most hardware peripherals
 #include STM32_HAL_H
+#include "pin.h"
 
 // The unique id address differs per MCU.  Ideally this define should
 // go in some MCU-specific header, but for now it lives here.
@@ -23,6 +24,7 @@
 #define GPIO_read_output_pin(gpio, pin) (((gpio)->ODR >> (pin)) & 1)
 
 void mp_hal_gpio_clock_enable(GPIO_TypeDef *gpio);
+bool mp_hal_gpio_set_af(const pin_obj_t *pin, GPIO_InitTypeDef *init, uint8_t fn, uint8_t unit);
 
 extern const unsigned char mp_hal_status_to_errno_table[4];
 

stmhal/pin.h

@@ -24,10 +24,14 @@
  * THE SOFTWARE.
  */
 
+#ifndef __MICROPY_INCLUDED_STMHAL_PIN_H__
+#define __MICROPY_INCLUDED_STMHAL_PIN_H__
+
 // This file requires pin_defs_xxx.h (which has port specific enums and
 // defines, so we include it here. It should never be included directly
 
 #include MICROPY_PIN_DEFS_PORT_H
+#include "py/obj.h"
 
 typedef struct {
   mp_obj_base_t base;
@@ -93,3 +97,5 @@ const pin_obj_t *pin_find_named_pin(const mp_obj_dict_t *named_pins, mp_obj_t na
 const pin_af_obj_t *pin_find_af(const pin_obj_t *pin, uint8_t fn, uint8_t unit);
 const pin_af_obj_t *pin_find_af_by_index(const pin_obj_t *pin, mp_uint_t af_idx);
 const pin_af_obj_t *pin_find_af_by_name(const pin_obj_t *pin, const char *name);
+
+#endif // __MICROPY_INCLUDED_STMHAL_PIN_H__