00034-BACKPORT-stm32f4-I2C-fix.patch

diff --git NuttX/nuttx/arch/arm/src/stm32/stm32f40xxx_i2c.c NuttX/nuttx/arch/arm/src/stm32/stm32f40xxx_i2c.c
index 2bb715c..481b851 100644
--- NuttX/nuttx/arch/arm/src/stm32/stm32f40xxx_i2c.c
+++ NuttX/nuttx/arch/arm/src/stm32/stm32f40xxx_i2c.c
@@ -1828,6 +1828,20 @@ static int stm32_i2c_isr(struct stm32_i2c_priv_s *priv)
    * the ISR cycle to handle the sending/receiving of the messages.
    */
 
+  /* First check for errors */
+
+  if ((status & I2C_SR1_ERRORMASK) != 0)
+    {
+         stm32_i2c_traceevent(priv, I2CEVENT_ERROR, status & I2C_SR1_ERRORMASK);
+
+         /* Clear interrupt flags */
+
+         stm32_i2c_putreg(priv, STM32_I2C_SR1_OFFSET, 0);
+
+         priv->dcnt = -1;
+         priv->msgc = 0;
+    }
+
   if (priv->dcnt == -1 && priv->msgc == 0)
     {
       i2cinfo("Shutting down I2C ISR\n");
@@ -2027,7 +2041,6 @@ static int stm32_i2c_transfer(FAR struct i2c_master_s *dev, FAR struct i2c_msg_s
                               int count)
 {
   FAR struct stm32_i2c_priv_s *priv = (struct stm32_i2c_priv_s *)dev;
-  stm32_i2c_sem_wait(priv);   /* Ensure that address or flags don't change meanwhile */
   uint32_t status = 0;
 #ifdef I2C1_FSMC_CONFLICT
   uint32_t ahbenr;
@@ -2035,6 +2048,7 @@ static int stm32_i2c_transfer(FAR struct i2c_master_s *dev, FAR struct i2c_msg_s
   int ret = 0;
 
   ASSERT(count);
+  stm32_i2c_sem_wait(priv);   /* Ensure that address or flags don't change meanwhile */
 
 #ifdef I2C1_FSMC_CONFLICT
   /* Disable FSMC that shares a pin with I2C1 (LBAR) */