diff --git a/drivers/video/max7456.c b/drivers/video/max7456.c
index 7bff2315616..7609223f789 100644
--- a/drivers/video/max7456.c
+++ b/drivers/video/max7456.c
@@ -391,7 +391,9 @@ static const struct file_operations g_mx7_debug_fops =
 
 static int node_from_name(FAR const char *name)
 {
-  for (int n = 0; n < NODE_MAP_LEN; n++)
+  int n;
+
+  for (n = 0; n < NODE_MAP_LEN; n++)
     {
       if (!strcmp(name, node_map[n].path))
         {
@@ -406,7 +408,9 @@ static int node_from_name(FAR const char *name)
 
 static int regaddr_from_name(FAR const char *name)
 {
-  for (int n = 0; n < REG_NAME_MAP_LEN; n++)
+  int n;
+
+  for (n = 0; n < REG_NAME_MAP_LEN; n++)
     {
       if (!strcmp(name, reg_name_map[n].path))
         {
@@ -1778,6 +1782,7 @@ int max7456_register(FAR const char *path, FAR struct mx7_config_s *config)
   FAR struct mx7_dev_s *dev = NULL;
   int ret = 0;
   int osdbl = 0;
+  int n;
 
   /* Without config info, we can't do anything. */
 
@@ -1845,7 +1850,7 @@ int max7456_register(FAR const char *path, FAR struct mx7_config_s *config)
    *    /dev/osd0/cm
    */
 
-  for (int n = 0; ret >= 0 && n < NODE_MAP_LEN; n++)
+  for (n = 0; ret >= 0 && n < NODE_MAP_LEN; n++)
     {
       ret = add_interface(path, node_map[n].path, &g_mx7_fops, 0666, dev);
     }
@@ -1857,7 +1862,7 @@ int max7456_register(FAR const char *path, FAR struct mx7_config_s *config)
    * activities.
    */
 
-  for (int n = 0; ret >= 0 && n < REG_NAME_MAP_LEN; n++)
+  for (n = 0; ret >= 0 && n < REG_NAME_MAP_LEN; n++)
     {
       ret = add_interface(path, reg_name_map[n].path, &g_mx7_debug_fops,
                           0666, dev);
@@ -1879,7 +1884,7 @@ int max7456_register(FAR const char *path, FAR struct mx7_config_s *config)
    */
 
   uint8_t buf[300];
-  for (int n = 0; n < sizeof(buf); n++)
+  for (n = 0; n < sizeof(buf); n++)
     {
       buf[n] = n;
     }
diff --git a/wireless/bluetooth/bt_smp.c b/wireless/bluetooth/bt_smp.c
index 6eeed94b823..4fcb5399b1d 100644
--- a/wireless/bluetooth/bt_smp.c
+++ b/wireless/bluetooth/bt_smp.c
@@ -1269,8 +1269,9 @@ static void swap_in_place(FAR uint8_t * buf, uint16_t len)
 static void array_shift(FAR const uint8_t *in, FAR uint8_t *out)
 {
   uint8_t overflow = 0;
+  int i;
 
-  for (int i = 15; i >= 0; i--)
+  for (i = 15; i >= 0; i--)
     {
       out[i] = in[i] << 1;
       /* previous byte */
@@ -1362,10 +1363,12 @@ static int bt_smp_aes_cmac(FAR const uint8_t *key, FAR const uint8_t *in,
   uint8_t flag;
   uint8_t n;
   int err;
+  int i;
 
   swap_buf(key, key_s, 16);
 
   /* (K1,K2) = Generate_Subkey(K) */
+
   err = cmac_subkey(key_s, k1, k2);
   if (err)
     {
@@ -1374,13 +1377,13 @@ static int bt_smp_aes_cmac(FAR const uint8_t *key, FAR const uint8_t *in,
 
   wlinfo("key %s subkeys k1 %s k2 %s\n", h(key, 16), h(k1, 16), h(k2, 16));
 
-  /* the number of blocks, n, is calculated, the block length is 16 bytes n =
+  /* The number of blocks, n, is calculated, the block length is 16 bytes n =
    * ceil(len/const_Bsize)
    */
 
   n = (len + 15) / 16;
 
-  /* check input length, flag indicate completed blocks */
+  /* Check input length, flag indicate completed blocks */
 
   if (n == 0)
     {
@@ -1407,7 +1410,8 @@ static int bt_smp_aes_cmac(FAR const uint8_t *key, FAR const uint8_t *in,
 
   wlinfo("len %u n %u flag %u\n", len, n, flag);
 
-  /* if flag is true then M_last = M_n XOR K1 */
+  /* If flag is true then M_last = M_n XOR K1 */
+
   if (flag)
     {
       xor_128((FAR struct uint128_s *)&in[16 * (n - 1)],
@@ -1425,15 +1429,17 @@ static int bt_smp_aes_cmac(FAR const uint8_t *key, FAR const uint8_t *in,
     }
 
   /* Reuse k1 and k2 buffers */
+
   x = k1;
   y = k2;
 
   /* Zeroing x */
+
   memset(x, 0, 16);
 
-  /* Rhe basic CBC-MAC is applied to M_1,...,M_{n-1},M_last */
+  /* The basic CBC-MAC is applied to M_1,...,M_{n-1},M_last */
 
-  for (int i = 0; i < n - 1; i++)
+  for (i = 0; i < n - 1; i++)
     {
       /* Y = X XOR M_i */
 
diff --git a/wireless/ieee802154/mac802154_data.c b/wireless/ieee802154/mac802154_data.c
index f43231b6606..d6ec56492be 100644
--- a/wireless/ieee802154/mac802154_data.c
+++ b/wireless/ieee802154/mac802154_data.c
@@ -136,12 +136,14 @@ int mac802154_req_data(MACHANDLE mac,
         }
       else if (meta->destaddr.mode == IEEE802154_ADDRMODE_EXTENDED)
         {
+          int index;
+
           /* The IEEE 802.15.4 Standard is confusing with regards to byte-order
            * for * extended address. More research discovers that the extended
            * address should be sent in reverse-canonical form.
            */
 
-          for (int index = IEEE802154_EADDRSIZE - 1; index >= 0; index--)
+          for (index = IEEE802154_EADDRSIZE - 1; index >= 0; index--)
             {
               frame->io_data[mhr_len++] = meta->destaddr.eaddr[index];
             }
@@ -202,12 +204,14 @@ int mac802154_req_data(MACHANDLE mac,
         }
       else if (meta->srcmode == IEEE802154_ADDRMODE_EXTENDED)
         {
+          int index;
+
           /* The IEEE 802.15.4 Standard is confusing with regards to byte-order
            * for * extended address. More research discovers that the extended
            * address should be sent in reverse-canonical form.
            */
 
-          for (int index = IEEE802154_EADDRSIZE - 1; index >= 0; index--)
+          for (index = IEEE802154_EADDRSIZE - 1; index >= 0; index--)
             {
               frame->io_data[mhr_len++] = priv->addr.eaddr[index];
             }