diff --git a/cpu/sam0_common/include/periph_cpu_common.h b/cpu/sam0_common/include/periph_cpu_common.h
index 1b01f68a86..a79010a369 100644
--- a/cpu/sam0_common/include/periph_cpu_common.h
+++ b/cpu/sam0_common/include/periph_cpu_common.h
@@ -402,6 +402,15 @@ typedef enum {
 
 /**
  * @brief   I2C device configuration
+ *          The frequency f() of the clock `gclk_src` must fulfill the condition
+ *
+ *              4 * speed ≤ f(gclk_src) ≤ 512 * speed
+ *
+ *          if speed ≤ 1 MHz and
+ *
+ *             12 * speed ≤ f(gclk_src) ≤ 520 * speed
+ *
+ *          if speed > 1 MHz
  */
 typedef struct {
     SercomI2cm *dev;        /**< pointer to the used I2C device */
diff --git a/cpu/sam0_common/periph/i2c.c b/cpu/sam0_common/periph/i2c.c
index c9cc275469..32f27207a5 100644
--- a/cpu/sam0_common/periph/i2c.c
+++ b/cpu/sam0_common/periph/i2c.c
@@ -80,6 +80,9 @@ void i2c_init(i2c_t dev)
 
     assert(dev < I2C_NUMOF);
 
+    const uint32_t fSCL = i2c_config[dev].speed;
+    const uint32_t fGCLK = sam0_gclk_freq(i2c_config[dev].gclk_src);
+
     /* Initialize mutex */
     mutex_init(&locks[dev]);
     /* DISABLE I2C MASTER */
@@ -122,30 +125,31 @@ void i2c_init(i2c_t dev)
     /* Enable Smart Mode (ACK is sent when DATA.DATA is read) */
     bus(dev)->CTRLB.reg = SERCOM_I2CM_CTRLB_SMEN;
 
-    /* Find and set baudrate. Read speed configuration. Set transfer
-     * speed: SERCOM_I2CM_CTRLA_SPEED(0): Standard-mode (Sm) up to 100
-     * kHz and Fast-mode (Fm) up to 400 kHz */
-    switch (i2c_config[dev].speed) {
-        case I2C_SPEED_NORMAL:
-        case I2C_SPEED_FAST:
-            bus(dev)->CTRLA.reg |= SERCOM_I2CM_CTRLA_SPEED(0);
-            break;
-        case I2C_SPEED_HIGH:
-            bus(dev)->CTRLA.reg |= SERCOM_I2CM_CTRLA_SPEED(2);
-            break;
-        default:
-            DEBUG("BAD BAUDRATE\n");
-            return;
+    /* Set SPEED */
+    if (fSCL > I2C_SPEED_FAST_PLUS) {
+        bus(dev)->CTRLA.reg |= SERCOM_I2CM_CTRLA_SPEED(2);
+    } else if (fSCL > I2C_SPEED_FAST) {
+        bus(dev)->CTRLA.reg |= SERCOM_I2CM_CTRLA_SPEED(1);
+    } else {
+        bus(dev)->CTRLA.reg |= SERCOM_I2CM_CTRLA_SPEED(0);
     }
+
     /* Get the baudrate */
-    tmp_baud = (int32_t)(((sam0_gclk_freq(i2c_config[dev].gclk_src) +
-               (2 * (i2c_config[dev].speed)) - 1) /
-               (2 * (i2c_config[dev].speed))) -
-               (i2c_config[dev].speed == I2C_SPEED_HIGH ? 1 : 5));
+    /* fSCL = fGCLK / (10 + 2 * BAUD)  -> BAUD   = fGCLK / (2 * fSCL) - 5 */
+    /* fSCL = fGCLK / (2 + 2 * HSBAUD) -> HSBAUD = fGCLK / (2 * fSCL) - 1 */
+    tmp_baud = (fGCLK + (2 * fSCL) - 1) /* round up */
+             / (2 * fSCL)
+             - (fSCL > I2C_SPEED_FAST_PLUS ? 1 : 5);
+
     /* Ensure baudrate is within limits */
-    if (tmp_baud < 255 && tmp_baud > 0) {
+    assert(tmp_baud < 255 && tmp_baud > 0);
+
+    if (fSCL > I2C_SPEED_FAST_PLUS) {
+        bus(dev)->BAUD.reg = SERCOM_I2CM_BAUD_HSBAUD(tmp_baud);
+    } else {
         bus(dev)->BAUD.reg = SERCOM_I2CM_BAUD_BAUD(tmp_baud);
     }
+
     /* ENABLE I2C MASTER */
     _i2c_poweron(dev);