stm32/i2c: Add support for I2C4 on H7 MCUs.

The current code assumes all I2Cs are on the same peripheral bus, which is
not true for I2C4 and the same goes for the clock enable code.
Signed-off-by: iabdalkader <i.abdalkader@gmail.com>

ports/stm32/i2c.c

@@ -285,8 +285,17 @@ int i2c_write(i2c_t *i2c, const uint8_t *src, size_t len, size_t next_len) {
 
 STATIC uint16_t i2c_timeout_ms[MICROPY_HW_MAX_I2C];
 
+static uint32_t i2c_get_id(i2c_t *i2c) {
+    #if defined(STM32H7)
+    if (i2c == I2C4) {
+        return 3;
+    }
+    #endif
+    return ((uint32_t)i2c - I2C1_BASE) / (I2C2_BASE - I2C1_BASE);
+}
+
 int i2c_init(i2c_t *i2c, mp_hal_pin_obj_t scl, mp_hal_pin_obj_t sda, uint32_t freq, uint16_t timeout_ms) {
-    uint32_t i2c_id = ((uint32_t)i2c - I2C1_BASE) / (I2C2_BASE - I2C1_BASE);
+    uint32_t i2c_id = i2c_get_id(i2c);
 
     // Init pins
     if (!mp_hal_pin_config_alt(scl, MP_HAL_PIN_MODE_ALT_OPEN_DRAIN, MP_HAL_PIN_PULL_UP, AF_FN_I2C, i2c_id + 1)) {
@@ -300,9 +309,22 @@ int i2c_init(i2c_t *i2c, mp_hal_pin_obj_t scl, mp_hal_pin_obj_t sda, uint32_t fr
     i2c_timeout_ms[i2c_id] = timeout_ms;
 
     // Enable I2C peripheral clock
-    RCC->APB1ENR |= RCC_APB1ENR_I2C1EN << i2c_id;
-    volatile uint32_t tmp = RCC->APB1ENR; // delay after RCC clock enable
+    volatile uint32_t tmp;
     (void)tmp;
+    switch (i2c_id) {
+        case 0:
+        case 1:
+        case 2:
+            RCC->APB1ENR |= RCC_APB1ENR_I2C1EN << i2c_id;
+            tmp = RCC->APB1ENR; // delay after RCC clock enable
+            break;
+        #if defined(STM32H7)
+        case 3:
+            RCC->APB4ENR |= RCC_APB4ENR_I2C4EN;
+            tmp = RCC->APB4ENR; // delay after RCC clock enable
+            break;
+        #endif
+    }
 
     // Initialise I2C peripheral
     i2c->CR1 = 0;
@@ -340,7 +362,8 @@ int i2c_init(i2c_t *i2c, mp_hal_pin_obj_t scl, mp_hal_pin_obj_t sda, uint32_t fr
 }
 
 STATIC int i2c_wait_cr2_clear(i2c_t *i2c, uint32_t mask) {
-    uint32_t i2c_id = ((uint32_t)i2c - I2C1_BASE) / (I2C2_BASE - I2C1_BASE);
+    uint32_t i2c_id = i2c_get_id(i2c);
+
     uint32_t t0 = HAL_GetTick();
     while (i2c->CR2 & mask) {
         if (HAL_GetTick() - t0 >= i2c_timeout_ms[i2c_id]) {
@@ -352,7 +375,8 @@ STATIC int i2c_wait_cr2_clear(i2c_t *i2c, uint32_t mask) {
 }
 
 STATIC int i2c_wait_isr_set(i2c_t *i2c, uint32_t mask) {
-    uint32_t i2c_id = ((uint32_t)i2c - I2C1_BASE) / (I2C2_BASE - I2C1_BASE);
+    uint32_t i2c_id = i2c_get_id(i2c);
+
     uint32_t t0 = HAL_GetTick();
     while (!(i2c->ISR & mask)) {
         if (HAL_GetTick() - t0 >= i2c_timeout_ms[i2c_id]) {