Merge pull request #80 from stm32-rs/fix_79

Fix a logic error

Author: datdenkikniet

src/dma/tx/descriptor.rs

@@ -135,7 +135,9 @@ impl TxDescriptor {
     fn set_buffer1_len(&mut self, len: usize) {
         unsafe {
             self.desc.modify(1, |w| {
-                (w & !TXDESC_1_TBS_MASK) | ((len as u32) << TXDESC_1_TBS_SHIFT)
+                let masked_len = w & !TXDESC_1_TBS_MASK;
+                let with_len = masked_len | ((len as u32) << TXDESC_1_TBS_SHIFT);
+                with_len
             });
         }
     }

src/dma/tx/mod.rs

@@ -80,7 +80,7 @@ impl<'ring> TxRing<'ring> {
 
     /// If this returns `true`, the next `send` will succeed.
     pub fn next_entry_available(&self) -> bool {
-        !self.entries[self.next_entry].is_available()
+        self.entries[self.next_entry].is_available()
     }
 
     /// Check if we can send the next TX entry.