diff --git a/sw/airborne/arch/lpc21/mcu_periph/i2c_arch.c b/sw/airborne/arch/lpc21/mcu_periph/i2c_arch.c
index 49c46ed1ab..eb990fdebe 100644
--- a/sw/airborne/arch/lpc21/mcu_periph/i2c_arch.c
+++ b/sw/airborne/arch/lpc21/mcu_periph/i2c_arch.c
@@ -342,6 +342,43 @@ bool_t i2c_submit(struct i2c_periph* p, struct i2c_transaction* t) {
 }
 
 void i2c_event(void) { }
-void i2c2_setbitrate(int bitrate __attribute__ ((unused))) { }
+void i2c_setbitrate(struct i2c_periph* p, int bitrate)
+{
+  int period = 15000000 / 2 / bitrate;
+  // Max 400kpbs
+  if (period < 19)
+    period = 19;
+  // Min 5kbps
+  if (period > 1500)
+    period = 1500;
+
+/* default clock speed 37.5KHz with our 15MHz PCLK
+   I2C1_CLOCK = PCLK / (I2C1_SCLL + I2C1_SCLH)     */
+
+#if (PCLK == 30000000)
+  period *= 2;
+#endif
+
+#if (PCLK == 60000000)
+  period *= 4;
+#endif
+
+#ifdef USE_I2C0
+  if (p == &i2c0)
+  {
+    /* set bitrate */
+    I2C0SCLL = period;
+    I2C0SCLH = period;
+  }
+#endif
+#ifdef USE_I2C1
+  if (p == &i2c1)
+  {
+    /* set bitrate */
+    I2C1SCLL = period;
+    I2C1SCLH = period;
+  }
+#endif
+}